Both Morus alba (Malus sieboldiana) and Morus australis (Malus sieboldiana) belong to the genus Morus in the family Moraceae and are deciduous shrubs commonly found along the edges of forests in Japan. Both are well-known for their use in sericulture (silkworm farming). Morphologically, a major characteristic is the presence of hairless upper surfaces on the leaves, with a mix of undivided leaves and lobed leaves with a distinctive 3 to 5 incisions. However, the two species are often confused and treated as if they were different varieties. In reality, they are completely different species biologically, with originally different distributions, and morphological differences are evident in their leaves, flowers, and fruits. Morus alba is more suitable for sericulture, while Morus australis is more suitable for food. This article will explain the classification and morphology of the genus Morus.

What are mulberries (Maguwa/Yamaguwa)?

Morus alba, also known as mulberry, mountain mulberry, or Chinese mulberry, is a deciduous tree native to central China. It was introduced worldwide for the purpose of raising silkworms (Bombyx mori), and in Japan, cultivated specimens have escaped cultivation (Kanagawa Prefecture Flora Survey Association, 2018).

The Japanese mulberry (Morus australis) is a deciduous tree distributed in Hokkaido, Honshu, Shikoku, Kyushu, and the Ryukyu Islands in Japan; Sakhalin; China; the Indochina Peninsula; India; and the Himalayas. It commonly grows in forest edges from mountainous areas to coastal regions and is cultivated for sericulture.

Both belong to the genus Morus in the family Moraceae and are deciduous shrubs that can be found in various places along the forest edges of Japan.

The leaves are easily recognizable by their granular dots or almost hairless appearance on the upper surface, their relatively straight lateral veins, and the fact that they consist of a mix of undivided leaves and lobed leaves with a distinctive 3 to 5 incisions.

This plant is dioecious, and rarely monoecious, so the flowers are unisexual, with separate male and female inflorescences, and are wind-pollinated (Taylor et al., 2006). The stamens of the male flower release elastic energy to actively disperse pollen. The female flower has four perianth segments.

The fruit is encased in a thick, fleshy perianth, and the ripe, dark purple mulberries are sometimes eaten.

Other characteristics include its branches being grayish-brown and almost hairless.

However, it is perhaps best known for its use as feed for silkworm larvae. Raw silk and silk produced from silkworms are important products, and they have been raised in Japan since ancient times. From the late Edo period until the production of synthetic fibers (from the 1870s to the mid-1930s), the export of raw silk supported Japan's modernization and was a valuable source of cash income for farmers (Settsu, 2017). A considerable number of mulberry trees were cultivated specifically for this purpose.

Although its use is limited these days, wild individuals can be seen in various places.

However, many articles describe mulberry and mountain mulberry as if they were simply different varieties, but biologically they are completely different species, and it seems some people are unaware of the differences.

It seems that these products are being sold interchangeably on sites like Amazon and Rakuten.

What is the difference between Morus alba and Morus serrata?

First, regarding the difference in distribution, the common mulberry (Morus edulis) is an introduced species, while the Japanese mulberry (Morus australis) is a native species. The common mulberry was introduced to Japan in ancient times for silkworms. However, in Japanese history textbooks, when the term "mulberry" is used, it almost always refers to the common mulberry due to its importance.

There are also several morphological differences (Hayashi, 2019; Kanagawa Prefecture Flora Survey Association, 2018).

Regarding the leaves, the differences are that in Morus alba (Morus serrulata), the leaf margins have blunt serrations, the leaf tips are not caudal, and the upper surface of the leaf is glossy, while in Morus australis (Morus erythrosora), the serrations on the leaf margins are very pointed, the leaf tips are caudal, and the upper surface of the leaf is usually less glossy.

However, it's important to note that there is also a variety of mulberry called *Morus serrata* f. maritima that grows on the coast and has nearly hairless, glossy leaves.

Some sources on the internet suggest that they can be distinguished by the notches in their leaves, but this is scientifically unproven and there is too much individual variation, so it's best not to rely on this method.

Regarding the flowers, there is a difference in that the pistil's style in *Malus sieboldiana* is two-lobed from the base, while in *Malus sieboldiana*, the style is two-lobed at the tip. This is a very subtle difference and may be difficult to observe.

Regarding the fruit, there is a difference in that the protrusion of the style (part of the pistil) does not remain in the mulberry tree, while it does remain in the wild mulberry tree.

Therefore, only in the Japanese mulberry (Morus australis) can you observe thin projections extending from various points between the aggregate fruits.

However, hybrids of Morus alba and Morus serrata are also said to exist, and there are intermediate individuals that are difficult to distinguish.

What are the differences in the uses of mulberry and wild mulberry?

Both the Japanese mulberry (Morus edulis) and the mountain mulberry (Morus serrata) have been used in sericulture (Tsujii, 2006).

However, while the Japanese mulberry (Morus edulis) is the most important tree species in sericulture, the Japanese mulberry (Morus serrata) has harder leaves than the Japanese mulberry, which slows down the growth of silkworms and is considered inferior as feed. Therefore, it was used when the Japanese mulberry was not growing well and there was a shortage of feed.

Therefore, it can be said that mulberry was overwhelmingly more important to humans.

However, as a wild edible plant, the Japanese mulberry (Morus serrulata) is more useful in Japan than the Japanese honeysuckle (Morus edulis). Its young shoots and leaves have been boiled and soaked in water before being eaten, and its fruit has been eaten raw or made into jam.

What are the differences between the genus *Mulberry* and *Broussonetia papyrifera*?

A genus very closely related to the mulberry genus is the paper mulberry genus, particularly the commonly seen species known as *Broussonetia papyrifera*.

Both plants produce lobed and unlobed leaves, have inconspicuous flowers that are wind-pollinated, and produce red, red fruits (aggregate fruits) that are mainly dispersed by birds, among other similarities.

However, in the genus Morus, the female flowers have four perianth segments, the upper surface of the leaves is dotted or almost hairless, the branches are grayish-brown and almost hairless, and the fruit is enclosed in a thickened, fleshy perianth. In contrast, in the genus Broussonetia papyrifera, including Broussonetia verniciflua, the female flowers have a tubular perianth segment that is 3-4 lobed at the tip, the upper surface of the leaves is densely or sparsely covered with short hairs, the branches are brown and have fine hairs, and the fruit has a fleshy pedicel.

Another difference is that the male inflorescences and aggregate fruits of the genus *Mulberry* are elongated, while those of the genus *Broussonetia papyrifera* are spherical.

Please see the separate article for information on the genus *Broussonetia*.

What are the differences between *Broussonetia papyrifera* and *Broussonetia kozoa*? Do *Broussonetia papyrifera* flowers burst open? What is the history of *Broussonetia papyrifera*? Are its fruits edible?

Both *Broussonetia papyrifera* and *Broussonetia erythrorhizon* have been used as paper since ancient times, and *Broussonetia papyrifera* can still be found in familiar green spaces today. However, some literature suggests that the distinction between these two species is not very clear, and they have historically been confused with each other. However...

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Are there any other similar types?

Morus cathayana resembles Morus australis, but is distributed only in western Japan, Korea, and China, and differs in that it has dense, short hairs on the underside of its leaves. It is mostly undivided.

Morus kagayamae is similar to Morus australis, but it is distributed only in the Izu Peninsula and the Izu Islands. It differs in that its leaves are somewhat thicker, the underside of the leaves is almost hairless, and the hair-like projections on the upper surface of the leaves are inconspicuous. Its serrations and lobes are sharper than those of Morus australis.

References

Hayashi, Masayuki. 2019. Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers, Tokyo. 824pp. ISBN: 9784635070447

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Taylor, PE, Card, G., House, J., Dickinson, MH, & Flagan, RC 2006. High-speed pollen release in the white mulberry tree, Morus alba L. Sexual Plant Reproduction 19: 19-24. http://doi.org/10.1007/s00497-006-0025-5.

Tsujii, Tatsuichi. 2006. Continued: Trees of Japan. Chuokoron-Shinsha, Tokyo. 230pp. ISBN: 9784121018342

Setsutsu, Hideki. 2017. Amazing! The hidden power of silkworms! Shining silk. Surface Science 38(3): 135-137. https://doi.org/10.1380/jsssj.38.135

Ficus microcarpa, Ficus serrata, and Ficus serrata all belong to the genus Ficus in the family Moraceae. They are distinguished from other Ficus species by their climbing habit, attaching themselves to tree trunks and rocks. Their most distinctive feature, like other Ficus species, is the formation of a fruit-like structure called a "syconium" (or syconium). The three species differ mainly in the shape of their leaves, and can also be distinguished by their syconium. It is known that only one species of parasitic wasp visits each syconium, a phenomenon known as "obligate pollination symbiosis." This article will explain the classification, morphology, and ecology of the subgenus Synoecia.

What are Himeitabi, Ooitabi, and Itabikazura?

Ficus thunbergii, also known as Himeitabi or Hime-gake-sekiryu, is distributed in Honshu (south of central Japan), Shikoku, Kyushu, and the Ryukyu Islands in Japan; and in Korea (Jeju Island). It is an evergreen vine (climbing woody plant) that grows in warm forests and forest edges, attached to tree trunks and rocks (Kanagawa Prefecture Flora Survey Association, 2018).

Ficus pumila, also known as giant fig or large cliff fig, is an evergreen climbing woody plant found on cliffs and rocks in warm regions of Japan (west of Chiba Prefecture), Shikoku, Kyushu, and the Ryukyu Islands; China, Taiwan, and Indochina. It is also cultivated in gardens for screening and greening walls.

Ficus sarmentosa subsp. nipponica var. nipponica, also known as rock fig vine, is distributed in Honshu (south of Fukushima and Niigata prefectures), Shikoku, Kyushu, and the Ryukyu Islands in Japan; as well as in Korea, China, and Taiwan. It is an evergreen climbing woody plant that grows in warm forests. It sends out roots from its branches, climbs trees and rocks, and often grows on stone walls of houses. Ficus nipponica is a synonym (former scientific name).

All of these species belong to the genus Ficus in the family Moraceae. They are distinguished from other species in the genus Ficus by their climbing habit, attaching themselves to tree trunks and rocks as epiphytes. They are collectively known as the subgenus Synoecia.

Its most distinctive feature, like other fig species, is the formation of a part that resembles a fruit. This is called a "syconium" (or "syconium inflorescence"), and it is actually a cluster of flowers that "blooms" inside it throughout the summer and even in the dead of winter.

After the flowers inside the syconium are pollinated, the mature syconium transforms into a "fruit sac." This is the same as what is commonly known as the "fig fruit" that is eaten.

These three species have inherited the characteristics of the fig genus while also acquiring climbing habits, but you may sometimes be confused about how to distinguish between them.

What are the differences between Ficus microcarpa, Ficus pumila, and Ficus serrata?

These three species can be distinguished mainly by the shape of their leaves (Kanagawa Prefecture Flora Survey Association, 2018).

While Ficus microcarpa and Ficus serrata have oval-shaped leaves with blunt tips, Ficus serrata has leaves that are ovate-elliptic to broadly lanceolate with long, pointed tips.

The difference between *Ficus microcarpa* and *Ficus serrata* lies in the fact that young *Ficus microcarpa* leaves have serrated edges, while mature leaves are oval-shaped with entire margins, and the lateral veins are at a 50-60° angle to the main vein, with 5-6 pairs. Mature leaves also have hairs on the veins on the underside. In contrast, *Ficus serrata* leaves are all entire, with lateral veins at a 30-40° angle to the main vein, with 4-5 pairs. Mature leaves are hairless.

There are many factors involved, but I think it's best to start by checking the hairs on the underside of the leaves.

The small leaves (juvenile leaves) of young Ficus microcarpa and Ficus serrata, with their swollen or indented spaces between the veins, are highly distinctive and unique, making them important for distinguishing them from other species.

Regarding the syconium (inflorescence), there are differences: in *Ficus microcarpa*, it is spherical with a diameter of 2 cm and a syconium stalk 0.5-1.5 cm long; in *Ficus pumila*, the fruit is spherical to obovate, becoming 3.5-5 cm long when mature, with a pedicel 0.5-1 cm long; and in *Ficus serrata*, the inflorescence is spherical, about 1 cm in diameter, and almost sessile.

Regarding Ficus microcarpa and Ficus serrata, one difference is that Ficus microcarpa has spreading hairs on its young branches, while Ficus serrata has hairs on its young branches and leaves initially, but later becomes hairless.

Are there any other similar types?

Many other species of fig are known. However, since the others are all upright species, you shouldn't have much trouble distinguishing them.

What's the difference between a banyan tree and a fig tree? Why is it called the "strangler fig"? Where are the flowers? Only one type of insect visits the flowers!? Where are the real fruits? It's an important food source for bats!?

The Japanese banyan tree (Ficus microcarpa) and the Japanese Ficus microcarpa (Ficus sylvestris) are known as two "strangler figs" in southern Japan, both producing drooping aerial roots and forming receptacles. Ecologically, they are similar, and it can be difficult to distinguish between them. However, there are significant differences in leaf venation and leaf length between the two. Also, regarding aerial roots...

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What's the difference between loquat (Biwa) and wild fig (Inubiwa)? How do they differ from apricots, persimmons, and mangoes? We'll explain how to distinguish between similar species! Insects and small birds visit loquat blossoms that bloom in winter!?

The loquat (Ficus microcarpa) is an evergreen tree native to China, cultivated worldwide for its edible fruit. In Japan, it is frequently cultivated not only for food but also for ornamental purposes. A similar-sounding species, the deciduous shrub known as *Ficus erecta*, is often confused with the loquat due to its oval-shaped, fruit-like structure...

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How is pollination done? Only one type of wasp comes!?

As mentioned above, the fig genus, which includes Ficus microcarpa, Ficus serrata, and Ficus philadelphicus, forms a part that resembles a fruit, and this is called a "syconium" (or "syconium inflorescence").

In reality, it's the part that contains the flowers, and it "blooms" inside it regardless of whether it's summer or the dead of winter.

Surprisingly, only one specific species of gall wasp (small bee) visits these flowers inside (Azuma et al, 2010).

Specifically, for Ficus microcarpa, it's Wiebesia sp.; for Ficus pumila, it's Wiebesia pumilae ; and for Ficus serrata, it's Wiebesia sp.

This type of symbiotic relationship involving almost one-to-one pollination is called "obligatory pollination symbiosis."

The specific process is described in a separate article.

What's the difference between a banyan tree and a fig tree? Why is it called the "strangler fig"? Where are the flowers? Only one type of insect visits the flowers!? Where are the real fruits? It's an important food source for bats!?

The Japanese banyan tree (Ficus microcarpa) and the Japanese Ficus microcarpa (Ficus sylvestris) are known as two "strangler figs" in southern Japan, both producing drooping aerial roots and forming receptacles. Ecologically, they are similar, and it can be difficult to distinguish between them. However, there are significant differences in leaf venation and leaf length between the two. Also, regarding aerial roots...

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What are the seed dispersal methods?

While it is certain that all three seed dispersal methods involve animal feeding, records of specific animals are insufficient. However, some records exist.

There are records of the fruit pods of Ficus microcarpa and Ficus serrata being eaten by Yakushima macaques (Otani, 2005) and by martens (Takatsuki, 2017).

There are records of the fruit sacs of *Ficus microcarpa* being eaten by *Flying Flying Fox* and *Flying Flying Fox* (Miyagi and Takahara, 2000).

The large fig (Ficus microcarpa) is clearly larger than the small fig (Ficus microcarpa) and the Japanese fig (Ficus serrata). It seems plausible that the small fig and the Japanese fig are mainly eaten by birds and small mammals, while the large fig is eaten by large mammals for seed dispersal. However, we await further research. The seed dispersal of the large fig on the mainland is something to be curious about.

References

Azuma, H., Harrison, RD, Nakamura, K., & Su, ZH 2010. Molecular phylogenies of figs and fig-pollinating wasps in the Ryukyu and Bonin (Ogasawara) islands, Japan. Genes & Genetic Systems 85(3): 177-192. https://doi.org/10.1266/ggs.85.177

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Takatsuki, Shigeki. 2017. Characteristics of fruits used by martens—a review. Mammalian Science 57(2): 337-347. https://doi.org/10.11238/mammalianscience.57.337

Miyagi, Tomoaki and Takahara, Kenji. 2000. On the plants of Sueyoshi Park and the food plants of the large bat. Bulletin of the Okinawa Prefectural Museum 26: 47-84. https://okimu.jp/userfiles/files/page/museum/issue/bulletin/kiyou26/26-4.pdf

Otani, T. 2005. Characteristics of medium-sized mammals as seed dispersers of berries—mainly using Japanese macaques as an example—. Nagoya University Journal of Forest Science 24: 7-43. https://doi.org/10.18999/nagufs.24.7

The loquat is an evergreen tree native to China, cultivated worldwide for its edible fruit. In Japan, it is frequently cultivated not only for food but also for ornamental purposes. A similar-sounding species, the dog loquat (Ficus erecta), is a deciduous shrub that is sometimes confused with the loquat due to its oval-shaped, fruit-like structure, but taxonomically they are completely different species. This difference can be seen in all organs, including flowers, fruits, and leaves. Loquats are also frequently searched for in relation to apricots, persimmons, and mangoes, perhaps because of the similar color of their fruits, but they differ in taste, fruiting season, and leaf shape. Loquat flowers bloom even in the middle of winter, and research in China has shown that insects visit in early winter, while bulbuls and white-eyes visit in late winter. It can be said that the loquat employs a hybrid strategy for pollination. This article will explain the classification and ecology of the loquat.

What are loquats and dog figs?

The loquat (Eriobotrya japonica), native to China, is an evergreen tree cultivated worldwide for its edible fruit (Mogi et al., 2000). In Japan, it has been documented since the Nara period and has been cultivated since at least that time, and is now planted in gardens and parks. Wild individuals are thought to be escaped cultivated individuals, but there are habitats in western Japan that appear to be wild, leading to the theory that it is a native species (Kanagawa Prefecture Flora Survey Association, 2018). However, in my opinion, this is not very reliable considering its global distribution. The Japanese name comes from the fact that the shape of the loquat fruit resembles the musical instrument biwa.

While the Japanese Wikipedia lists the loquat's scientific name as Rhaphiolepis bibas, placing it within the genus Rhaphiolepis, subsequent molecular phylogenetic studies have reaffirmed the prevailing view that the genera Rhaphiolepis and loquat should be separated (Dong et al., 2022), and globally, Eriobotrya japonica is considered the correct scientific name (RBG Kew, 2024).

Ficus erecta, also known as the dog loquat, is distributed in Honshu (west of the Kanto region), Shikoku, Kyushu, and the Ryukyu Islands in Japan; and in Korea (Jeju Island). It is a deciduous shrub that grows in forests of oak and chestnut trees and is common near the coast.

Since they all share the name "loquat," you might get the impression that they are somewhat closely related.

It could be argued that they share the common characteristic of producing an oval-shaped, edible part on the plant body when it matures in the wild.

What is the difference between loquat and dog fig?

However, taxonomically speaking, loquats and wild figs are completely different species, and it's difficult to find any similarities between them.

While the loquat (Biwa) belongs to the genus Eriobotrya in the family Rosaceae, the wild fig (Ficus erecta) belongs to the genus Ficus in the family Moraceae.

One of the most significant differences is that while the loquat tree has actual flowers and fruits attached to its plant body, the wild fig (Ficus erecta) has what are called "syconia" or "syconium" instead of flowers and fruits.

This syconium is a structure unique to the fig genus, with flowers blooming inside the sac-like part. Only a small wasp called Blastophaga nipponica enters the syconium and contributes to pollination (Azuma et al, 2003; Azuma et al, 2010). This relationship is called "obligatory pollination symbiosis." For more details on this relationship, please see the separate article.

What's the difference between a banyan tree and a fig tree? Why is it called the "strangler fig"? Where are the flowers? Only one type of insect visits the flowers!? Where are the real fruits? It's an important food source for bats!?

The Japanese banyan tree (Ficus microcarpa) and the Japanese Ficus microcarpa (Ficus sylvestris) are known as two "strangler figs" in southern Japan, both producing drooping aerial roots and forming receptacles. Ecologically, they are similar, and it can be difficult to distinguish between them. However, there are significant differences in leaf venation and leaf length between the two. Also, regarding aerial roots...

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When ripe, the flower receptacle transforms into a "fruit receptacle," and the flowers inside develop into the fruit. In other words, the true fruit of the fig tree is located inside the fruit receptacle.

On the other hand, the loquat has flowers with five white petals in a conical inflorescence, and its fruit is a yellow-orange pome-shaped fruit.

Therefore, you can see that the characteristics of the flowers and fruits of the loquat and the dog fig are completely different. The "dog" in dog fig means useless, and while it's not that the dog fig is inedible to humans, it's not as tasty as the loquat.

The leaves are also completely different: the loquat leaves are broadly oblanceolate to narrowly obovate with serrated edges and prominent downy hairs, while the wild fig leaves are obovate with entire margins and lack downy hairs.

Furthermore, while the loquat tree (Ficus microcarpa) is monoecious (having both male and female flowers on the same plant), the wild fig (Ficus erecta) is dioecious (having separate male and female flowers on different plants).

While no other species of the genus Loquat are known in Japan, numerous species are known in China (Wu et al., 2003).

What are the differences between loquats, apricots, persimmons, and mangoes?

Looking at the suggestions in Google Search, it seems many people are curious about the differences between loquats, apricots (Prunus armeniaca var. ansu), persimmons (Diospyros kaki), and mangoes (Mangifera indica).

To someone who has observed them carefully, it might seem that there is no way to confuse them, but since both have yellowish fruits, some people might not be able to tell the difference, so I will briefly explain the differences here.

First, in terms of classification, loquats and apricots belong to the Rosaceae family, persimmons to the Ebenaceae family, and mangoes to the Anacardiaceae family. Therefore, with the exception of loquats and apricots, they are quite distantly related, and the basic structures of their leaves and flowers differ significantly. We will omit the detailed differences here, but you can see that they have completely different shapes by looking at the following photos.

The shape and taste of the fruit are as follows:

Loquat fruits are broadly oval-shaped, pear-like fruits, 3-4 cm in diameter. They ripen to a yellowish-orange color around May or June. The taste is mildly sweet with a refreshing flavor.

Apricots are drupe fruits, about 3 cm in diameter. They ripen to a yellow to dark yellow color around June or July. The taste is intensely sour, while the closely related apricot is also sour but also quite sweet. They are usually eaten in the form of dried apricots.

The fruit of the persimmon tree is a berry, 3.5 to 8.5 cm in diameter (cultivated varieties can grow to over 10 cm). It ripens to a yellowish-red color around October to November. It has a crisp, refreshing sweetness and a crunchy texture.

Mango fruits are drupe-like fruits, broadly oval to comma-shaped, measuring 3-25 cm in length and 1.5-15 cm in width, with size varying depending on the variety. They ripen from mid-April to around July, turning green or yellow to pink. The taste varies depending on the variety, but the apple mango, common in Japan, is very sweet and has a rich aroma.

For more information about these plants, please see our other article.

There's a difference between apricots and plums! What are the differences between plums, cherries, and Japanese apricots? We'll explain how to distinguish between similar species! Why do they bloom between plums and cherries? The fruit's toxicity didn't affect birds!?

Apricots and apricots are familiar foods because their fruits are often eaten as dried fruit. They are often treated as the same thing, and "apricot" is commonly used as the English name for "apricot." However, this is not always correct. Biologically, they are very closely related...

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What are the differences between persimmon (Diospyros kaki), Japanese persimmon (Diospyros serrata), and mountain persimmon (Diospyros margaritacea)? We'll explain how to distinguish between similar species! Where are they native to? What's the difference between astringent and sweet persimmons? What insects visit the flowers? Who eats them in nature?

The Japanese persimmon (kaki) has been cultivated in Japan since ancient times and is a fruit and plant strongly associated with Japanese culture. While closely related species exist, the Japanese persimmon is easily distinguishable by the size of its fruit. However, when distinguishing by leaves alone, it resembles the Japanese dwarf persimmon (Diospyros kaki), the Ryukyu dwarf persimmon (Diospyros ryukyuensis), and the evergreen persimmon (Diospyros kaki), and subtle differences...

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How are loquats pollinated? What animals visit the flowers that bloom in winter?

Loquats are slightly self-compatible and can self-pollinate to a limited extent, but it has been found that cross-pollination improves fruit set rate and quality in terms of fruit size, fruit weight, seed count, flesh weight, and sugar content (Khan et al., 2022). Simply put, if you let insects or other means pollinate the fruit, you will get more delicious fruit.

Loquats bloom from November to January, producing around 100 small, fragrant flowers in a conical inflorescence 10-20 cm long. The flowers are about 1 cm in diameter and have five white petals. The lower inner part of the petals, the calyx, and the inflorescence are densely covered with brownish downy hairs.

While it's rare for plants to bloom in winter, how do they manage pollination? There should be fewer animals that act as pollinators during winter.

Loquats are commercially cultivated as fruit trees all over the world, so research on this topic is quite advanced. It's interesting that loquats are more popular as fruit trees in other countries than in Japan.

A study in Jordan found that European honeybees, a species of the genus *Hymenoptera*, and a species of the genus *Bumblebee* visit flowers (Freihat et al., 2008). A study in Islamabad, Pakistan, found that houseflies, calliflies, syrphidae, and honeybees visit flowers (Sarwar et al., 2012). A study in Punjab, Pakistan, found that honeybees, pygmy bees, and syrphidae visit flowers (Ahmad et al., 2021).

Except for Jordan, which has a Mediterranean climate, it can be seen that, generally speaking, small insects that are resistant to winter cold are the ones that visit the flowers.

However, these results are from records outside of the native habitat. The pollination ecology of loquats has also been studied in China, their native country, and some interesting results have been obtained there (Fang et al., 2012).

This study found that in early winter, as in other countries, insects such as the Oriental honeybee (Apis cerana), the Asian hornet (Vespa velutina), calliflies (Calliphoridae), and syrphidae (Hyrphidae) visited flowers. However, in late winter, the number of insects decreased, and it was found that birds such as the brown-eared bulbul (Pycnonotus sinensis) and the Japanese white-eye (Zosterops japonicus) became the main pollinators. Furthermore, the experiment revealed that their contribution to pollination was quite significant. For both birds and birds, the main food source was nectar.

Loquat blossoms secrete abundant nectar for a long period, making them a good food source for birds, but they also emit a pleasant scent. Since birds are thought to have a very weak sense of smell, this characteristic is thought to be an adaptation to attract insects.

In summary, these results from its native habitat suggest that loquat flowers have evolved to attract both small, cold-hardy insects and birds.

References

Ahmad, S., Khalofah, A., Khan, SA, Khan, KA, Jilani, MJ, Hussain, T., … & Ahmad, Z. 2021. Effects of native pollinator communities on the physiological and chemical parameters of loquat tree (Eriobotrya japonica) under open field condition. Saudi Journal of Biological Sciences 28(6): 3235-3241. ISSN: 1319-562X, https://doi.org/10.1016/j.sjbs.2021.02.062

Azuma, H., Harrison, RD, Nakamura, K., & Su, ZH 2010. Molecular phylogenies of figs and fig-pollinating wasps in the Ryukyu and Bonin (Ogasawara) islands, Japan. Genes & Genetic Systems 85(3): 177-192. ISSN: 1341-7568, https://doi.org/10.1266/ggs.85.177

Higashi, Koji; Su, Zhihui; and Nakamura, Keiko. 2003. Co-evolution of the genus Ficus and fig wasps. Mathematical Sciences 479: 78-83. ISSN: 0386-2240, https://www.saiensu.co.jp/search/?isbn=4910054690538&y=2003

Dong, Z., Qu, S., Landrein, S., Yu, WB, Xin, J., Zhao, W., … & Xin, P. 2022. Increasing taxa sampling provides new insights on the phylogenetic relationship between Eriobotrya and Rhaphiolepis. Frontiers in Genetics 13: 831206. ISSN: 1664-8021, https://doi.org/10.3389/fgene.2022.831206

Fang, Q., Chen, YZ, & Huang, SQ 2012. Generalist passerine pollination of a winter-flowering fruit tree in central China. Annals of Botany 109(2): 379-384. ISSN: 0305-7364, https://doi.org/10.1093/aob/mcr293

Freihat, NM, Al-Ghzawi, AAM, Zaitoun, S., & Alqudah, A. 2008. Fruit set and quality of loquats (Eriobotrya japonica) as effected by pollinations under sub-humid Mediterranean. Scientia Horticulturae 117(1): 58-62. ISSN: 0304-4238, https://doi.org/10.1016/j.scienta.2008.03.012

Khan, SA, Tanveer, M., Ahmad, S., Mars, M., Naeem, M., Naveed, Z., … & Goulson, D. 2022. Declining abundance of pollinating insects drives falls in loquat (Eriobotrya japonica) fruit yields in the Pothwar region of Pakistan. Agriculture, Ecosystems & Environment 339: 108138. ISSN: 1873-2305, https://doi.org/10.1016/j.agee.2022.108138

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Mogi, T., Ishii, H., Sakio, H., Katsuyama, T., Ota, K., Takahashi, H., Shirokawa, S., and Nakagawa, S. 2000. Flowers Blooming on Trees: Polypetalous Flowers (Vol. 1, Revised 3rd Edition). Yama-kei Publishers, Tokyo. 719pp. ISBN: 9784635070034

RBG Kew. 2024. The International Plant Names Index and World Checklist of Vascular Plants. Plants of the World Online. http://www.ipni.org and https://powo.science.kew.org/

Sarwar, G., Raja, S., Mahmood, R., Stephen, E., & Munawar, MS 2012. Fruit setting and yield of loquats (Eriobotrya japonica) as affected by pollinators. Pakistan Entomologist 34(1): 43-46. ISSN: 1017-1827, https://www.pakentomol.com/cms/pages/tables/upload/file/5a042f8c731b4008.pdf

Wu, ZY, Raven, PH & Hong, DY (Eds.). 2003. Flora of China (Vol. 9 Pittosporaceae through Connaraceae). Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis. ISBN: 9781930723146

Both the Bodhi tree (Tilia japonica) and the large-leaved Bodhi tree (Tilia maximowicziana) are deciduous trees belonging to the genus Tilia in the Malvaceae family. Although they have different origins, they are both cultivated in cities throughout Japan, and their leaf shapes are very similar, so those who have never seen them may not be able to distinguish them. However, there are significant differences not only in the size of the leaves but also in the length of the petioles. A closely related species in the same genus is the Japanese linden (Tilia japonica), but this can be distinguished by the brown hairs in the vein axils on the underside of the leaves and the shape of the flowers. They are often confused with the Indian Bodhi tree due to their names, but the Indian Bodhi tree belongs to the Moraceae family and has completely different leaf and flower shapes. Originally, the tree under which Gautama Siddhartha (Buddha) attained enlightenment was the Indian Bodhi tree, but because the Indian Bodhi tree does not grow in Japan, this species was imported from China as a substitute for planting in temples, resulting in the names being reversed. The inflorescences of the Bodhi tree and the large-leaved Bodhi tree hang downwards, and the flowers are small and white, but they have a strong scent that seems to attract many bees. The fruit is a nut, and there are bracts at the base of the inflorescence. When it falls, it rotates, moving away from the mother tree and thus dispersing the seeds. This article will explain the classification, morphology, pollination ecology, and seed dispersal of linden and large-leaved linden.

What are the linden tree and the large-leaved linden tree?

The Bodhi tree (Tilia miqueliana) is a deciduous tree distributed in China (Wu et al., 2007). In Japan, it is cultivated mainly in temples as a substitute for the sacred Indian Bodhi tree.

Tilia mandshurica, also known as the large-leaved linden tree, is distributed in Hokkaido, the Tohoku and Hokuriku regions of Honshu, and the northern part of the Kanto region of Japan. It is a deciduous tree that grows in deciduous forests in mountainous areas (Mogi et al., 2000). It is sometimes cultivated as a park tree or street tree in colder regions.

Both are deciduous trees belonging to the genus Tilia in the Malvaceae family. Although they have different origins, they share the commonality of being cultivated in cities across Japan. Their names are also similar, and those who have never seen them may not be able to distinguish between them. They also share the characteristic of having leaves that can be heart-shaped, and a venation pattern called "palmate venation," where the veins spread out from the base of the petiole throughout the leaf.

What are the differences between the Japanese linden (Tilia japonica), the large-leaved linden (Tilia japonica), and the Japanese linden (Tilia japonica)?

Before discussing the differences between the two species, it's worth noting that the same genus includes a plant called Tilia japonica (Japanese linden tree). Tilia japonica is endemic to Japan, distributed across Hokkaido, Honshu, Shikoku, and Kyushu, and is a deciduous tree that grows from mountain ridges to streams.

What are the differences between the Japanese linden tree (Tilia japonica), the large-leaved linden tree (Tilia japonica), and the Japanese linden tree (Tilia japonica)?

First, the leaf shape differs: in the linden tree, the leaves are distorted heart-shaped with few wrinkles on the upper surface, while in the Japanese linden, they are triangular to heart-shaped, and in the large-leaved linden, the upper surface of the leaves is very wrinkled (Hayashi, 2019).

In linden trees, there are clusters of brown hairs in the vein axils on the underside of the leaves, and these are particularly noticeable at the base of the petiole, where the leaves appear to be covered in brown hairs. This is absent in Japanese linden trees, and while it is common in large-leaved linden trees, it remains light brown.

The most distinctive feature is the flowers: in the linden tree, the stamens clearly protrude outward from the petals, while in the Japanese linden and large-leaved linden, the stamens are not as long and curve inward.

What is the difference between a linden tree and an Indian linden tree?

The Indian fig tree (Ficus religiosa) is another species that is often mistaken for the fig tree due to its name. The Indian fig tree is a semi-deciduous tree distributed from India to Southeast Asia.

The Indian fig tree is taxonomically completely different from the common fig tree (Tilia japonica). As mentioned above, the common fig tree belongs to the genus Tilia, while the Indian fig tree belongs to the genus Ficus in the family Moraceae.

Therefore, there are many differences. First, regarding the leaves, the Indian fig (Ficus lyrata), like other fig species, has thick, entire leaves with very long, tail-like tips that can extend more than a third of the leaf blade, whereas the leaves of the linden tree (Tilia japonica) and other Tilia species are thinner, serrated, and while the tips are tail-like, they are quite short.

The flowers differ further; the Indian fig tree, like many fig species, produces special flowers called "syconium" or "syconium" that resemble fruits, while the linden tree and other Tilia species have typical open flowers.

While the Indian linden tree, like its relatives the banyan tree and the fig tree, can become a "strangler fig," the fact that this doesn't happen with the Tilia genus is a significant advantage.

What's the difference between a banyan tree and a fig tree? Why is it called the "strangler fig"? Where are the flowers? Only one type of insect visits the flowers!? Where are the real fruits? It's an important food source for bats!?

The Japanese banyan tree (Ficus microcarpa) and the Japanese Ficus microcarpa (Ficus sylvestris) are known as two "strangler figs" in southern Japan, both producing drooping aerial roots and forming flower receptacles. Ecologically, they are similar, and it can be difficult to distinguish between them. However, there are significant differences in leaf venation and leaf length between the two. Also, regarding aerial roots...

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So why do they have such similar names despite being so different?

The Japanese word for linden tree, Bodhiju, is written with the kanji characters "菩提樹," where "Bodhi" is a transliteration of a Sanskrit word meaning the state of enlightenment attained by Buddha. It originates from the fact that it was the tree under which Gautama Siddhartha (Shakyamuni), the founder of Buddhism, attained enlightenment, although originally that tree was the Indian linden tree (Iwasa, 1982; Tsumega, 1990; Kurita, 2008).

However, since the Indian fig tree is native to the tropics and does not grow in Japan, fig trees imported from China were used as a substitute for planting in temples. This resulted in the confusing situation of the Japanese names being reversed. There is a theory that it was Eisai, the founder of the Rinzai school of Zen Buddhism, who brought them back (Kurita, 2008). If so, this would have been during the Southern Song dynasty in China and the Heian period in Japan.

However, it's unclear why the "Bodhi tree" was chosen from among the many plants. Perhaps it was simply because its leaves resembled those of a tail (Tsumaga, 1990), but this explanation is not very convincing and remains unclear in my research.

It is also considered a sacred tree in Hinduism (Iwasa, 1982).

What is the difference between a linden tree and a large-leaved linden tree?

There are many differences between the Japanese linden tree and the large-leaved linden tree (in the broad sense) (Hayashi, 2019).

First, as mentioned above, the Bodhi tree (Ficus microcarpa) is native to China and is mainly planted around temples, while the large-leaved Bodhi tree (Ficus serrata) grows wild in Japan. Therefore, wild specimens are likely to be large-leaved Bodhi trees. However, since large-leaved Bodhi trees are also sometimes planted, it may be difficult to distinguish them from planted specimens.

In terms of morphological differences, as the name suggests, the leaf blade size of the Japanese linden is 5-10 cm, while that of the large-leaved linden is considerably larger, at 7-18 cm.

A more striking difference is the length of the petioles: while those of the common linden tree are only 2-4 cm long, those of the large-leaved linden tree are 4-7 cm long, making them noticeable even from a distance. I think this is a good difference, as there is no overlap between the two species.

While the leaves of the Japanese linden tree (Tilia japonica) are triangular to heart-shaped, those of the large-leaved linden tree (Tilia maximowicziana) are round to heart-shaped.

Furthermore, while the large-leaved linden has clusters of light brown hairs in the vein axils on the underside of its leaves, the common linden lacks this feature.

While the flowers of the Japanese linden (Tilia japonica) tend to be yellowish-brown, those of the large-leaved linden (Tilia maximowicziana) are usually white to pale yellow. However, the morphological differences are minimal, making it difficult to use this distinction for species identification.

In addition, there is a known species called Tilia mandshurica var. mandshurica, which is distributed in the Chugoku region and Oita Prefecture of Japan, as well as the Korean Peninsula, Northeast China, and Russia (Siberia). However, although this species has stellate hairs covering the entire underside of its leaves, like Tilia maximowicziana, it completely lacks the light brown hair clusters in the vein axils on the underside of the leaves that are present in Tilia maximowicziana.

What are the varieties of the large-leaved linden tree?

Two varieties of the large-leaved linden (in the broad sense) are known.

The underside of the leaves of Tilia maximowicziana (in the narrow sense) is densely covered with stellate hairs, giving it a whitish appearance.

The underside of the leaves of Linden moss var. yesoana has sparse stellate hairs and is somewhat green.

What is the structure of a flower?

Like many other species in the Tilia genus, the flowers of the Japanese linden (Tilia japonica) and the large-leaved Japanese linden (Tilia japonica) hang down in drooping cymose inflorescences, bearing numerous small white to yellow flowers. While the shape of the flowers themselves is not particularly unusual, the presence of bracts at the base of the inflorescence is distinctive. These are used during fruit development.

The linden tree blooms in June. Bracts are borne in the leaf axils at the tips of the branches, and cymose inflorescences hang down from near the center of the bracts, bearing 3 to 12 (up to 20) flowers. The cymose inflorescences are 6 to 10 cm long. The bracts have short petioles (sometimes sessile), are spatulate in shape, 5 to 8 (up to 12) cm long, have a blunt apex, and a narrowly cuneate base, with stellate hairs on both surfaces and densely covering the underside. The flowers are pale yellow and fragrant. The pedicels are 4 to 6 cm long, and the pedicels are 8 to 12 mm long. The sepals are 5 to 6 mm long. The petals are slightly longer than the sepals. There are 5 stamens and 5 staminodes.

The large-leaved linden tree flowers from June to July. It hangs down cymose inflorescences 6-10 cm long from the sides of the base of the petioles, bearing more than ten pale yellow flowers at the end. Narrowly oblong involucral bracts are fused to the axis of the inflorescence. The involucral bracts are 5-8 cm long when in flower, densely covered with stellate hairs on both sides, and have short stalks 2-5 mm long at the base. There are five sepals, lanceolate in shape, 6-7 mm long, with pointed tips, and densely covered with long hairs on the inner surface and stellate hairs on the back. There are five pale yellow petals, narrowly oblong in shape, about 8 mm long, with slightly blunt tips. There are many stamens, about 5 mm long, and they are free. Inside the petals are five staminodes, which are spatulate, petal-like, and shorter than the petals. The ovary has five chambers, each containing two ovules, and the style is slender and elongated, with the stigma shallowly divided into five lobes.

How is pollination done?

The linden tree (Tilia japonica) and the large-leaved linden tree (Tilia maximowicziana) have fragrant flowers and produce abundant nectar, clearly indicating that they are insect-pollinated, just like other members of the Tilia genus.

In literature, there are records of the beetle Ceresium sinicum visiting linden trees (Ikeda, 2016). There are also records of European honeybees visiting (Sasaki, 2010), but since European honeybees are an invasive species, they would not contribute to pollination in the wild.

On the internet, the Kyoto University Museum database contains specimens of a species of mud dauber wasp and a species of ancient bumblebee collected from a linden tree (Kyoto University Museum, 2023), and one blog features a photograph of a yellow-breasted bumblebee visiting the tree (waiwai, 2010).

In literature, there are records of bumblebees such as the Japanese bumblebee (Bombus ignitus) and the small bumblebee (Bombus spp.) frequently visiting the Japanese linden tree (Tilia japonica) (Mizui, 1993). There are also records of European honeybees visiting the tree, and honey made from its single-flower nectar is sometimes sold (Sasaki, 2010; Masaka et al., 2013). Although European honeybees are an introduced species, they do provide benefits to humans.

In summary, while longhorn beetles are an exception, it seems that many types of bees are attracted to these flowers. The reason why, despite the flowers not having any special structure, is not fully understood, but the secret likely lies in their scent. A Chinese study detected a total of 70 volatile components in the flowers of winter linden (T. cordata), linden, and silver linden (T. tomentosa), and identified 43 aromatic compounds (Bao & Shen, 2022). These may be what strongly attracts bees.

What is the structure of the fruit?

The fruits of the Japanese linden (Tilia japonica) and the large-leaved linden (Tilia japonica) are also nuts, as is common with many other species in the Tilia genus. A nut is a fruit in which a hard, woody pericarp encloses a single seed and does not split open.

However, the unique feature is the presence of bracts at the base of the inflorescence; in the large-leaved linden, the flowers eventually elongate to a length of 6-10 cm when they develop into fruits.

The linden tree's nuts are spherical, 7-8 mm in diameter, hard, and densely covered with fine, stellate hairs on their surface.

The nuts of the large-leaved linden tree are spherical or oval in shape, 10-15 mm long, with five ridges, and densely covered with short, grayish-white hairs. They mature around October and contain a single seed without splitting open.

What are the seed dispersal methods?

The genus Tilia is dispersed by wind through its bracts (Manchester, 1994), and this is thought to be the case for Tilia japonica and Tilia maximowicziana as well (Azuma & Yasuda, 1989; Nonoda et al., 2008).

However, unlike many wind-dispersed plants where the fruit or seeds fall to the ground and are then carried away by the wind, in the genus Tilia, the inflorescence below the bracts is separated, and the distorted bracts, caught in the wind's resistance, rotate as they fall, slowly moving through the air and away from the mother tree.

In other words, it can be said that this is a seed dispersal method very similar to that of samaras of genera such as maple, hornbeam, cypress, fir tree, and tulip tree (Johnson, 1988; Azuma & Yasuda, 1989). This seed dispersal method seems to be possible precisely because it is a tall tree.

References

Azuma, A., & Yasuda, K. (1989). Flight performance of rotary seeds. Journal of Theoretical Biology, 138 (1), 23-53. https://doi.org/10.1016/S0022-5193(89)80176-6

Bao, W., & Shen, Y. (2022). Dynamic Changes on Floral Aroma Composition of the Three Species from Tilia at Different Flowering Stages. Horticulturae, 8 (8), 719. https://doi.org/10.3390/horticulturae8080719

Hayashi, Masayuki. (2019). Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers. ISBN: 9784635070447

Ikeda, Dai. (2016). Additional records of *Tetsuirohimekamikiri* from Hyogo Prefecture. *Kiberihamushi*, 38 (2), 48. ISSN: 1884-9377, https://www.konchukan.net/pdf/kiberihamushi/Vol38_2/kiberihamushi_38_2_48.pdf

Iwasa, Shunkichi. (1982). Sketches of Tropical Crops (VIII): Religious Trees. Tropical Forestry, 63, 33-36. https://doi.org/10.32205/ttf.0.63_33

Johnson, WC (1988). Estimating dispersibility of Acer, Fraxinus and Tilia in fragmented landscapes from patterns of seedling establishment. Landscape Ecology, 1, 175-187. https://doi.org/10.1007/BF00162743

Kurita, W. (2008). This Month's Tree: The Linden. Green Power, 353, 3. ISSN: 0389-0988, https://doi.org/10.11501/12524798

Kyoto University Museum. (July 1, 2023). Insects - Natural History Specimens. Kyoto University Museum website. https://www.museum.kyoto-u.ac.jp/collection/Konchu/html/index_Konchu.html

Manchester, SR (1994). Inflorescence bracts of fossil and extant Tilia in North America, Europe, and Asia: patterns of morphologic divergence and biogeographic history. American Journal of Botany, 81 (9), 1176-1185. https://doi.org/10.1002/j.1537-2197.1994.tb15612.x

Masaka, K., Sato, T., & Tanahashi, Ikuko. (2013). Actual utilization of tree nectar sources by beekeeping: Diversity and regional characteristics in Hokkaido. Journal of the Japanese Forestry Society, 95 (1), 15-22. https://doi.org/10.4005/jjfs.95.15

Tsumega, Kaneo. (1990). National Flowers of the World. Hoikusha. ISBN: 9784586507917, https://doi.org/10.11501/13645920

Mizui, Norio. (1993). Ecological studies on seed propagation of deciduous broad-leaved trees. Research Report of Hokkaido Forestry Experiment Station, 30, 1-67. ISSN: 0910-3945, https://agriknowledge.affrc.go.jp/RN/2030500320

Mogi, Toru; Ota, Kazuo; Katsuyama, Teruo; Takahashi, Hideo; Shirokawa, Shiro; Yoshiyama, Hiroshi; Ishii, Hidemi; Sakio, Hitoshi; and Nakagawa, Shigetoshi. (2000). Flowers Blooming on Trees: Polypetalous Flowers (Vol. 2, 2nd edition). Yama-kei Publishers. ISBN: 9784635070041

Nonoda, S., Shibuya, M., Saito, H., Ishibashi, S., & Takahashi, M. (2008). Invasion and growth process of broad-leaved trees in fir plantations and the effects of thinning. Journal of the Japanese Forestry Society, 90(2), 103-110. https://doi.org/10.4005/jjfs.90.103

Sasaki, Masami. 2010. The World of Flowers as Seen by Bees: Nectar-Producing Plants of the Four Seasons and Gifts from Honeybees. Kaiyusha. ISBN: 9784905930273

waiwai. (June 19, 2010). Linden tree and bumblebee. Cat's Days. http://nekobiyori.cocolog-nifty.com/days/2010/06/post-4d5a.html

Wu, ZY, Raven, PH, & Hong, DY (Eds.). (2007). Flora of China (Vol. 12 Hippocastanaceae through Theaceae). Science Press, and Missouri Botanical Garden Press. ISBN: 9781930723641

Both *Broussonetia papyrifera* and *Broussonetia kozoa* have been used as paper since ancient times, and *Broussonetia papyrifera* is still a common sight in green spaces today. However, some literature suggests that the distinction between the two species is not very clear, and they have historically been confused. Recent research, however, has shown that they can be clearly distinguished. The length of the petiole is the most important factor, and the presence or absence of fruit can also be a distinguishing factor. The hybrid *Broussonetia papyrifera* likely originated in Eurasia and was brought to Japan. The exact time when *Broussonetia papyrifera* was introduced to Japan is unclear, but it already appears in the Kojiki, Nihon Shoki, and Manyoshu from the Nara period. In Japan, it has been used as a symbol of the sacred, as well as a raw material for cloth and washi paper. The flowers of *Broussonetia papyrifera* have evolved to be wind-pollinated, and it is said that the male inflorescence disperses pollen by "popping". The fruit is an aggregate fruit and is orange-red, so it looks delicious to the human eye, but according to people who have actually eaten it, it is not tasty. However, it seems to be a delicacy for wild mammals and birds. This article will explain the classification, history, pollination ecology, and seed dispersal of paper mulberry (Broussonetia papyrifera) and paper mulberry (Broussonetia erythrorhizon).

Himekozo and Kozo are confusing!

Broussonetia monoica, also known as Himekozo, is a deciduous shrub found in forest edges, roadsides, and wastelands in hilly and low mountainous areas of Japan (south of Iwate Prefecture), Shikoku, and Kyushu; as well as in Korea and China (Mogi et al., 2000).

On the other hand, Broussonetia x kazinoki is a deciduous shrub or small tree said to be a hybrid of Broussonetia papyrifera, which belongs to the same genus as Broussonetia humilis (Kanagawa Prefecture Flora Survey Association, 2018). It is mainly a cultivated species, but occasionally escapes into the wild.

These two species, both belonging to the genus *Broussonetia papyrifera* in the family Moraceae, are often confused and their distinctions are not very clear (Hosoki, 2005).

What is the difference between *Broussonetia papyrifera* and *Broussonetia kozoa*?

However, recent studies have shown that they can be clearly distinguished (Kanagawa Prefecture Flora Survey Association, 2018).

The petioles of *Broussonetia papyrifera* are 0.5-1 cm long, and it is monoecious, so fruiting is frequently observed. On the other hand, *Broussonetia kozoa* has petioles 1-3 cm long, is dioecious, and rarely produces fruit. Incidentally, the petioles of the closely related *Broussonetia mulberry* are 3-10 cm long and covered with many coarse hairs, so it seems that they can be roughly distinguished by checking the petioles.

How did the paper mulberry hybrid come into existence?

But how did the paper mulberry hybrid come into existence?

The Japanese paper mulberry (Broussonetia papyrifera) is a native species, while the Japanese paper mulberry (Broussonetia comatus) is a cultivated species introduced to Japan. Therefore, there are two possible origins for paper mulberry in Japan.

First, there's the theory that the native Japanese paper mulberry (Broussonetia papyrifera) and the introduced paper mulberry (Broussonetia comatus) hybridized in Japan.

Another theory is that the Eurasian paper mulberry and the Eurasian paper mulberry hybridized on the Eurasian continent (either in China or Korea).

This matter has long remained unresolved, and descriptions vary from one literature to another. However, recent research using DNA sequences as genetic markers suggests the latter possibility (Won, 2019). In other words, it is believed that the paper mulberry, which originated in Eurasia, was brought to Japan.

Are there any other similar species? What's the difference between this and a mulberry tree?

The genus Morus, including Morus australis and Morus serrata, is known to be very closely related to the genus Broussonetia papyrifera. Both species produce lobed and unlobed leaves, have inconspicuous flowers that are wind-pollinated, and their fruits (aggregate fruits) ripen red and are mainly dispersed by birds, among other similarities.

However, while the genus *Broussonetia* has noticeable hairs on the upper surface of its leaves, the genus *Morus* has almost none.

Please see the separate article for more details.

What are the differences between Morus alba, Morus serrata, and Broussonetia papyrifera? We'll explain how to distinguish between these similar species!

Both Morus alba and Morus serrata belong to the genus Morus in the family Moraceae and are deciduous shrubs commonly found along the edges of forests in Japan. Both are well-known for their use in sericulture (silkworm farming). Morphologically, a major characteristic is the presence of hairless upper leaves, a mix of undivided leaves and lobed leaves with a distinctive 3-5 incisions. However, 2...

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How has paper mulberry been used in Japan? What is its history?

Paper mulberry (Kozo) has long been cultivated in China, Korea, and Japan, primarily as a fiber-producing plant (Won, 2019). In China, it is used not only for fiber but also as animal feed, food additives, and in traditional medicine. The exact time when paper mulberry was introduced to Japan is unclear (Tanaka et al., 2018). In the past, there was no distinction between paper mulberry, paper mulberry, and cranberry. Therefore, although it is a plant with a long history in Japan, it is not known which specific plant was used.

The paper mulberry tree, as a general term, appears in Japan's oldest books, including the Kojiki, Nihon Shoki, and Manyoshu. The Nihon Shoki mentions that ropes made from paper mulberry were used in the construction of Izumo Taisha Shrine, and that they were an important material for tying the pillars together (Arioka, 2018). The Kojiki also mentions its use as a lifeline for harvesting abalone and turban shells.

Another use is for cotton (yu), which is made by steaming the skin, soaking it in water, tearing it into thread, and then bleaching it to make it white. This white color is considered pure and sacred, and has been used in Shinto rituals for sacred objects such as nusa.

Furthermore, it is also used as a raw material for making cloth. Cloth woven from mulberry fibers was called "futobu" and was a valuable type of clothing throughout Japan until cotton, made from cotton fibers, became widespread during the Edo period. There was also "kamifu," which was made by cutting paper after it had been made into paper, and weaving it into thread. It seems to have been the finest fabric because it was breathable and durable.

As for washi (Japanese paper), it seems that papermaking techniques were introduced to Japan in the early 7th century during the Asuka period by Doncho, a monk from Goguryeo (present-day Korea) (Mizumura et al., 2015; Arioka, 2018). Some believe that this was the first time kozo (paper mulberry) in the narrow sense was brought to Japan.

As a raw material for washi paper, it has been the most commonly used because it is cheaper than ganpi or mitsumata.

What are the differences between Mitsumata and Ganpi? We'll explain how to distinguish between these similar species! Why is Mitsumata used as the raw material for Japanese banknotes? Do flowers require insects with long mouths to thrive?

Both Mitsumata and Ganpi belong to the Thymelaeaceae family and are used to make washi (Japanese paper). Their flowers are quite similar in shape. However, despite being in the same family, Mitsumata and Ganpi belong to different genera, and a closer examination of their flowering periods and inflorescence shapes reveals various differences. Ganpi was the first to be used for washi...

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Since the early modern period, it has been most important as shoji paper, such as Mino paper. This may be the most familiar use for us today.

Did flowers release pollen by "bursting"?

The flowers of the paper mulberry bloom from April to May, with male inflorescences in the leaf axils at the base of new branches and female inflorescences in the leaf axils at the top. The male inflorescences have stalks about 1 cm long and are spherical in shape with a diameter of about 1 cm, while the female inflorescences have shorter stalks and are spherical in shape with a diameter of about 5 mm, and are characterized by their prominent reddish-purple pistils.

What's most unusual is that it produces male and female flowers separately on the same plant. This is called "monoecious" in technical terms (Shimizu, 2001). While it's relatively common for male and female flowers to bloom separately on different plants, this particular type of flowering is quite rare, wouldn't you say?

Now, this shape is widely seen in the genus *Broussonetia*, but how do they disperse their pollen? It's so inconspicuous that it seems unlikely to be noticed by insects.

Research suggests that members of the genus Paper Brick (Broussonetia papyrifera) are pollinated by wind (Knuth et al., 1906; Tanaka, 2000; Won, 2019). Wind-pollinated flowers have several characteristics, and Paper Brick (Broussonetia papyrifera) particularly meets these conditions well, including (1) low pollen viscosity, (2) significant differences in morphology and color between male and female inflorescences, (3) exposed anthers on the stigma, and (4) a feathery or brush-like stigma on the pistil. These features make the pollen more easily carried by the wind, and the flower shape makes it more susceptible to wind, making it highly adapted for wind dispersal.

Furthermore, several types of wind pollination have been identified, including the "rebound type" in which the filaments, initially bent towards the center of the flower, instantly bend back and release pollen into the air through centrifugal force; the "long filament type" in which the anthers are attached to the end of the long, slender filaments and the anthers are dispersed by the wind; and the "strong wind type" in which pollen is dispersed by strong winds. However, according to research, flowers of the genus Paper Bush are classified as the "rebound type".

However, I couldn't find any description of how the paper mulberry species "bursts open." Perhaps the male inflorescences are small and clustered together, and it might be possible to observe them bursting open over time. Those with time to observe closely might make new discoveries!

The characteristic of "forming male inflorescences in the leaf axils at the base of new branches and female inflorescences in the upper leaf axils" is likely a mechanism to prevent pollen from falling immediately from top to bottom, thus making self-pollination less likely.

Fruit tastes bad when humans eat it, doesn't it...?

The fruit of the paper mulberry is an aggregate fruit, meaning that multiple fruits are clustered together to form a single fruit. It is spherical, 1-1.5 cm in diameter, and ripens to an orange-red color in June and July. At first glance, it looks delicious, but it has been described as having an unpleasant texture (Mogi et al., 2000) and the juice of the fruit is viscous and sweet when eaten, but not particularly tasty (Hosoki, 2005), suggesting it's not to human liking. There doesn't seem to be a comprehensive study of animals that actually eat it in the wild, but there are records of Asiatic black bears, martens, and raccoons eating it (Koike and Masaki, 2008; Takatsuki, 2018). It has also been used by the invasive species, the Japanese squirrel (Yoshida et al., 2009), suggesting it is a popular fruit at least among mammals.

However, it is common to see many young trees growing at the edge of forests near human settlements. This suggests that the seeds are also being eaten by birds, and some studies treat this as bird dispersal (Obata, 2007). Although I could not find any studies that specifically identified the species, one blog had a photo of a Japanese white-eye eating the seeds (Shiki in the Garden, 2023), suggesting that seed dispersal may be carried out by both mammals and birds.

On the other hand, as mentioned above, paper mulberry rarely produces fruit, and its seeds are known to have very low establishment and germination rates, making it difficult for it to propagate in the wild (Won, 2019). In cultivation, it is propagated vegetatively.

References

Arioka, Toshiyuki. 2018. Cultural History of Things and People 181: Washi Plants. Hosei University Press, Tokyo. 317pp. ISBN: 9784588218118

Obata, Hidehiro. 2007. Construction Examples Utilizing Topsoil Seed Banks in Spraying (VI) – Differences in Invasive Woody Plant Species Between the Center of the Slope and the Forest Edge. Journal of the Japanese Society of Landscape Architecture 33(3): 498-501. https://doi.org/10.7211/jjsrt.33.498

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Knuth, P., Müller, H., & Ainsworth Davis, JR 1906. Handbook of flower pollination: based upon Hermann Müller's work 'The fertilization of flowers by insects'. Clarendon Press, Oxford. 383pp. ISBN: 9781362641742, https://doi.org/10.5962/bhl.title.54973

Koike, Shinsuke & Masaki, Takashi. 2008. A literature review of woody plant fruit utilization by three species of carnivorous plants south of Honshu. Journal of the Japanese Forestry Society 90(1): 26-35. ISSN: 1349-8509, https://doi.org/10.4005/jjfs.90.26

Mizumura, M., Kubo, T., & Moriki, T., 2015. Japanese paper: History, development and use in Western paper conservation. In: F. Whymark (Ed.), Adapt & Evolve 2015: East Asian Materials and Techniques in Western Conservation (Proceedings from the International Conference of the Icon Book & Paper Group) (pp. 43-59). The Institute of Conservation. https://www.icon.org.uk/resource/japanese-paper-history-development-and-use-in-western-paper-conservation.html

Mogi, T., Ishii, H., Sakio, H., Katsuyama, T., Ota, K., Takahashi, H., Shirokawa, S., and Nakagawa, Shigetoshi. 2000. Flowers Blooming on Trees: Polypetalous Flowers (Vol. 1, Revised 3rd Edition). Yama-kei Publishers, Tokyo. 719pp. ISBN: 9784635070034

The Four Seasons in My Garden. June 5, 2023. A Japanese white-eye pecking at the fruit of a paper mulberry tree. The Four Seasons in My Garden. https://kumagai9320.hatenablog.com/entry/5333eeaa58067910c7261e0981dfc250

Shimizu, Takemi. 2001. Illustrated Dictionary of Botanical Terms. Yasaka Shobo, Tokyo. xii, 323pp. ISBN: 9784896944792

Hosoki, Daisuke. 2005. Paper mulberry (Broussonetia kazinoki Sieb.). Journal of the Japanese Society of Green Technology 30(3): 590. ISSN: 0916-7439, http://www.jsrt.jp/pdf/dokomade/30-3kouzo.pdf

Tanaka, Hajime. 2000. Pollen size and dispersal mode of wind-pollinated angiosperms. Journal of Plant Research 75(2): 116-122. ISSN: 0022-2062, https://doi.org/10.51033/jjapbot.75_2_9406

Tanaka, Motomu; Shishikura, Satoshi; and Togashi, Akira. 2018. Lifestyle Crafts Series: Utilizing Local Resources - Paper Mulberry and Mitsumata. Agricultural, Forestry and Fisheries Culture Association, Tokyo. 142pp. ISBN: 9784540171154

Takatsuki, Shigeki. 2018. Characteristics of fruits used by raccoons—a review. Mammalian Science 58(2): 237-246. ISSN: 0385-437X, https://doi.org/10.11238/mammalianscience.58.237

Yoshida, Yukiko; Yamane, Akiomi; and Iwata, Ryutaro. 2009. Diet of Callosciurus erythraeus in Zushi City, Kanagawa Prefecture. Journal of Forest Wildlife Research 34: 7-11. ISSN: 0916-8265, https://doi.org/10.18987/jjwrs.34.0_7

Won, H. 2019. Test of the hybrid origin of Broussonetia × kazinoki (Moraceae) in Korea using molecular markers. Korean Journal of Plant Taxonomy 49(4): 282-293. ISSN: 1225-8318, https://doi.org/10.11110/kjpt.2019.49.4.282

Ficus microcarpa (Akou) and Ficus benghalensis (Gajumaru) are known as two "strangler figs" in southern Japan, characterized by their drooping aerial roots and the formation of syconium receptacles. Ecologically, they are similar, and it can be difficult to distinguish between them. However, there are significant differences in leaf veins and leaf length between Akou and Gajumaru. There are also differences in how they extend their aerial roots. Ecologically, while Akou is indeed a "strangler fig," it can also grow independently. On the other hand, Gajumaru appears quite aggressive, attempting to strangle other trees even after strangling them. So where are the flowers of these two species? At first glance, Akou and Gajumaru produce what appear to be "fruits," leading you to believe they don't have flowers. However, these "fruit-like" structures are called syconium receptacles, and the actual flowers are hidden inside. Only one specific species of dwarf wasp visits these receptacles. This flower doesn't simply pass on pollen and nectar to insects; instead, it provides its female flowers as food for the larvae of fig wasps, which attract adult female wasps to lay their eggs. Meanwhile, the banyan tree and the fig tree complete pollination during the wasp's migration. This kind of relationship is widely observed in the fig genus and represents co-evolution. After pollination, the syconium transforms into a fruit sac, and then the seeds are dispersed by birds or fruit bats. This article will explain the classification, life history, pollination ecology, and seed dispersal of the banyan tree and the fig tree.

Two species found in southern Japan that produce drooping aerial roots and syconia.

Ficus superba, also known as Akou, is an evergreen tree distributed along the coasts of Shikoku, Kyushu, and the Ryukyu Islands in Japan, as well as from Southeast Asia to southern China. It grows in lowland tropical rainforests and on rocky areas and outcrops of limestone where other plants have difficulty growing (Tsuchiya & Miyagi, 1991; Otani, 2020). One theory about its Japanese name is that its small red fruit resembles a baby ("ako" in the Wakayama and Kochi dialects).

The banyan tree , Ficus microcarpa, is also known as the banyan tree (Yōju). It is distributed in the southwestern islands of Japan, south of Yakushima and Tanegashima; southern China; Taiwan; Bhutan; India; Sri Lanka; Nepal; Southeast Asia (Malaysia; Myanmar; Thailand; Vietnam); New Guinea; and northern Australia. It is an evergreen tree that grows in mountainous and lowland areas. One theory about its Japanese name is that it is a corrupted form of the word "karumaru," meaning "to entangle" or "to get tangled," referring to the appearance of its trunk and aerial roots.

Both belong to the fig genus of the Moraceae family and are distributed in southern Japan. They are similar in that they have three prominent veins at the base of their leaves, hang down aerial roots, and produce round, swollen organs called receptacles. In addition, unlike other fig species in Japan such as Ficus erecta, both are monoecious, meaning they have both male and female flowers on the same plant.

What is the difference between a Ficus microcarpa and a banyan tree?

However, there are significant differences in leaf shape between the Ficus microcarpa and the banyan tree (Hayashi, 2014).

In the Ficus microcarpa (Ako), the lateral veins are clearly visible throughout the leaf, with few parts growing at an obtuse angle from the main vein, and countless parts growing in a reticulate pattern. In contrast, in the Ficus benghalensis (Gajumaru), the lateral veins are faint and inconspicuous, there are many parts growing at an obtuse angle from the main vein, and the reticulate pattern is hardly visible.

In short, the Ficus microcarpa (Akou) has finer, more detailed leaf veins that can be seen.

In Ficus microcarpa, the three-veined pattern is clearly visible on both the upper and lower surfaces of the leaf, but in Ficus benghalensis, it may not be prominent on the upper surface of the leaf, but is clearly visible on the lower surface.

Furthermore, while the leaf blades of the Ficus microcarpa are long, measuring 10-20 cm and the petioles 2-7 cm, the leaf blades of the Ficus benghalensis are short, measuring 4-10 cm and the petioles 1-2 cm.

There are also differences in how they develop their aerial roots.

While the banyan tree (Ficus microcarpa) often extends long, octopus-tentacle-like aerial roots from low places and creeps along rocks, the Japanese banyan tree (Ficus serrata) usually hangs down thin, string-like aerial roots from high places.

Let's confirm the above.

In addition, Taiwan is also known for a variety of banyan tree called Ficus microcarpa f. crassifolia, which has particularly round leaves.

While there are many other known species in the fig genus, such as Ficus erecta, the species found on the Japanese mainland can be distinguished from the two species mentioned above by the fact that the base of the leaves is shallowly indented or the veins on the underside of the leaves are three-dimensional.

Are there any other similar types?

The fig genus includes many species, so it's necessary to distinguish between them. Please see the separate article for more details.

What's the difference between loquat (Biwa) and wild fig (Inubiwa)? How do they differ from apricots, persimmons, and mangoes? We'll explain how to distinguish between similar species! Insects and small birds visit loquat blossoms that bloom in winter!?

The loquat (Ficus microcarpa) is an evergreen tree native to China, cultivated worldwide for its edible fruit. In Japan, it is frequently cultivated not only for food but also for ornamental purposes. A similar-sounding species, the deciduous shrub known as *Ficus erecta*, is often confused with the loquat due to its oval-shaped, fruit-like structure...

ecological-information.com

What are the differences between *Ficus microcarpa*, *Ficus pumila*, and *Ficus serrata*? We explain how to distinguish between similar species! What is the special parasitic wasp that visits the "fruit-like" "syconium"?

Ficus microcarpa, Ficus serrata, and Ficus serrata all belong to the Ficus genus of the Moraceae family. They are distinguished from other Ficus species by their climbing growth habit, attaching themselves to tree trunks and rocks. Their most distinctive feature, like other Ficus species, is the formation of fruit-like structures...

ecological-information.com

Was the banyan tree a opportunistic "strangler fig"?

The banyan tree is often called the "strangler fig." Why is that?

After the fruits of the banyan tree are eaten by birds and other animals while they are still in the tree, the seeds are excreted in their droppings and fall into the base of branches or hollows in the trunks of trees such as the Japanese red tree and palm trees. The seeds germinate and become epiphytic, extending aerial roots downwards until they reach the ground (Tsuchiya and Miyagi, 1991; Otani, 2006).

From here, it grows thicker and thicker aerial roots, eventually covering the parent tree and, incredibly, killing it. For this reason, it is sometimes called the "strangler fig."

One way it differs from other plants is that its roots are completely exposed above ground, and it grows downwards. However, unlike mistletoe and similar plants, it doesn't steal nutrients; rather, it physically takes away areas that are more suitable for photosynthesis.

Furthermore, this does not mean that all individuals "strangle" their prey. Some individuals that are fortunate enough to grow in suitable locations such as Yakushima and the Ryukyu Islands, where the roots do not dry out easily and there is moisture along streams, climb onto rock faces, and sometimes concrete retaining walls, to obtain sunlight.

Is the banyan tree's method of "strangling" more intense than that of the fig tree?

The banyan tree is also a "strangler fig" (Maeshiro, 1988). Therefore, in the same way as the fig tree, it falls into the base of branches or hollows in the trunk of a tree, germinates and takes root, extends aerial roots downwards, and strangles the parent tree.

However, unlike the banyan tree, the Ficus microcarpa produces prop roots (aerial roots that support the roots) (Katanoda and Ohno, 1999).

In the early stages of the banyan tree, the aerial roots play a role called "adhesive aerial roots," which germinate, attach to the trunk, grow downwards, and constrict the parent tree (Maeshiro, 1988).

However, as the tree ages, the aerial roots increase in the number of "pillar-type aerial roots," and their role changes. In other words, after strangling the parent tree, they increase the number of aerial roots that cling to the ground, stone walls, or limestone like pillars, so that the tree can survive even if the parent tree's trunk is damaged or rots.

Furthermore, in the case of the banyan tree, there is another pattern of strangulation that differs from that of the fig tree.

Unlike the banyan tree (Ficus microcarpa), the banyan tree (Ficus microcarpa) has thin, string-like aerial roots that hang down from high places. These are called "suspending aerial roots" and they emerge from the attached or supportive aerial roots once they have grown to a certain extent.

If a tree is directly beneath aerial roots, it will be entangled and strangled to death. Since this strangulation occurs after the tree has grown to a certain extent, it could be considered quite cruel.

Putting all this information together, it seems that the banyan tree (Ficus microcarpa) is an opportunistic "strangler fig," while the Ficus microcarpa (Gajumaru) is a stronger, absolute "strangler fig."

Is it true that banyan trees like the Japanese Ficus microcarpa and the Ficus regia don't have flowers?

At first glance, you won't find the "flowers" that we usually see on banyan trees like the Ficus microcarpa. Instead, round, swollen parts that resemble "fruits" appear directly on the plant and can be seen for an extended period.

This is a characteristic common to the fig genus. The fig also shares this characteristic, and its name is written with the kanji characters for "flowerless fruit," which comes from the fact that it appears to produce fruit without flowering.

So, do fig trees really not have flowers and just produce fruit directly?

Years of research by scientists have shown that this is not the case.

The part that resembles a fruit is called a "syconium" (or "syconium inflorescence"), and it is known that it "blooms" inside even in summer and the dead of winter.

This becomes clear when you actually cut the flower receptacle in half and examine its interior.

Inside, you can find pollen released from the stamens and ovules, which are precursors to seeds. If it were a fruit, you wouldn't be able to observe these things.

Both the banyan tree (Ficus microcarpa) and the Japanese Ficus (Ficus sieboldii) produce syconia year-round in the wild, but they become particularly numerous from around springtime. Since the syconia grow directly on the trunk, they are called "cauliflory."

Inside, it produces male and female flowers, waiting for insects. But are there really any insects that would come to such an invisible flower?

Years of research have revealed that the only insects that visit these flowers are Platyscapa ishiiana in the case of the Ficus microcarpa and Eupristina verticillata in the case of the Ficus benghalensis.

This type of symbiotic relationship involving almost one-to-one pollination is called "obligatory pollination symbiosis."

How do banyan trees like the fig tree and the Ficus microcarpa pollinate using dwarf wasps?

Let's look at the specific process of pollination (Otani, 2020; Borges, 2021).

Banyan trees like the fig tree and the Ficus microcarpa form syconium, and each syconium initially produces female flowers (female phase). Female parasitic wasps visit these female flowers. However, they don't come to find food like nectar or pollen, as is common with other pollinating insects. The female parasitic wasps visit the syconium with the purpose of laying eggs in the female flowers to feed their larvae. When these female parasitic wasps leave another syconium, they have pollen on their bodies. The reason for this will become clear later.

The tip of the flower receptacle has tiny holes, through which female wasps fly in and enter the receptacle. At this time, the female wasps have pollen from other individuals on their bodies, so they pollinate the female flowers, and the banyan or fig tree is successfully pollinated.

The female wasp lays her eggs in the female flower and then dies. Female wasps hatch from fertilized eggs, and male wasps hatch from unfertilized eggs.

One to several months later, the hatched parasitic wasp larvae will feed on the female flowers. Female flowers contain ovules, which are precursors to seeds, making them a very nutritious and excellent food source.

By the way, you might think that this would mean that even the pollinated female flowers would be eaten, but female flowers are produced with the understanding that they will be eaten, and extra sterile ones are produced to serve as food for the larvae of the parasitic wasps.

In this way, the grown parasitic wasps mate inside the flower receptacle. Usually, multiple female parasitic wasps are present, so there is generally no need to worry about inbreeding.

On the syconium side of banyan trees like the fig tree (Ficus microcarpa) and Ficus benghalensis, the male flowers bloom around the time the larval stage of the parasitic wasps becomes adults (male phase). When the female parasitic wasps become adults, they emerge from the syconium, receiving pollen from the male flowers and flying away. It's a very well-designed cycle. On the other hand, the males have vestigial wings and spend their entire lives inside the syconium where they were born.

The female parasitic wasps that escape will then invade another syconium that is bearing a female flower. This cycle is necessary, which is why they need to produce syconiums all year round.

By the way, what happens if a female parasitic wasp invades a syconium while it is producing male flowers? Male and female syconiums are almost indistinguishable in appearance.

While it's not fully understood in the case of Ficus microcarpa and Banyan trees, in closely related species, the female parasitic wasp is unable to lay eggs and dies without leaving any offspring. Although it appears to be a highly symbiotic relationship, a closer look reveals that it's not necessarily a win-win situation.

However, in the case of banyan trees and fig trees, newly emerged adults are able to escape, so perhaps they are also able to escape.

The "obligate pollination symbiosis" system common to the fig genus

The nearly one-to-one obligate pollination symbiosis practiced by Ficus microcarpa and Banyan trees is widely observed in the Ficus genus and the Ficus parasitic family, and is known to promote co-evolution (Azuma et al, 2003; Azuma et al, 2010).

Co-evolution refers to the phenomenon where, in conjunction with the diversification of species in one taxonomic group, species in another taxonomic group also diversify in a coordinated manner.

It's difficult to explain how this relationship came about, but it's thought to have originated in tropical regions with abundant resources and no distinct seasons, which may have been a major advantage for obligate pollination symbiosis.

Specifically, the following arrangements apply to the different types of products in Japan.

• Fig (Ficus carica) vs. Fig wasp (Blastophaga psenes)
• Ficus erecta vs. Blastophaga nipponica (Ficus erecta wasp)
• Ficus septica vs. Ceratosolen bisulcatus
• Ficus benguetensis vs. Ceratosolen cornutus
• Giant Ficus pumila vs. Giant Ficus Wasp Wiebesia pumilae
• Ficus thunbergii vs. Wiebesia sp.
• Ficus irisana vs. Kradibia commuta (Ficus irisana wasp)
• Ficus ampelas vs. Kradibia sumatrana (Ficus ampelas vs. Ficus sumatrana)
• Ficus virgata vs. Liporrhopalum philippinensis

These absolute pollination symbiotic systems are maintained in much the same way, but there are a few slight differences.

Unlike other fig species in Japan, such as the Japanese Ficus microcarpa (Ficus erecta), the Japanese banyan tree (Ficus mongolica) and the Japanese fig (Ficus canaliculata) are monoecious, meaning they undergo pollination as described above. However, most other fig species are dioecious (having separate male and female plants).

Therefore, there are male and female plants, and pollination occurs in a similar but slightly different way than described above.

The flower receptacle transforms into a fruit receptacle, and the seeds are dispersed by birds and bats.

After pollination, the mature flower receptacle transforms into a fruit receptacle. This is the same fruit that is commonly known as the "fig fruit" that is eaten.

Since the flowers were located inside the syconium, the actual fruit must be located inside the fruit sac.

The fruit sacs of both the banyan tree and the fig tree ripen to a yellow or pale pink color.

Generally, fig species with red pods are eaten by monkeys and birds with well-developed color vision, while fig species with green pods tend to emit an odor and are eaten by most other mammals, including bats (Harrison et al., 2012). In either case, the seeds are dispersed via animal feces.

In the case of banyan trees such as the Japanese fig (Ficus microcarpa) and the Ficus mongolica, it is said that their seeds are dispersed by birds, as evidenced by the change in their color.

It is also known that Yakushima macaques like it (Otani, 2005).

However, other studies have shown that birds and monkeys are not the only ones that eat these fruit sacs. Fruit bats, which primarily feed on nectar and fruit, also eat the fruit sacs and play an important role in seed dispersal (Miyagi and Takahara, 2000).

Studies conducted in the Southwest Islands have confirmed that all four species of flying foxes—the Erabu flying fox, the Orii flying fox, the Yaeyama flying fox, and the Daito flying fox—feed on the fruit sacs of the Ficus microcarpa and the banyan tree.

The fruit sacs of the Ficus microcarpa and Banyan tree are a form of "cauliflorous fruit" that develops from cauliflorous flowers. Therefore, they are attached closely to the trunk or branches. It is generally believed that cauliflorous fruit has the effect of making it easier for animals such as fruit bats to eat the fruit (in this case, the fruit sac) by perching on the trunk or sturdy branches (Van der Pijl, 1961).

Considering their ecology, this seems to apply well to the Ficus microcarpa and the banyan tree as well.

However, a study conducted by an American research group presents a different view (Harrison et al., 2012). They examined numerous species of the fig subgenus Sycomorus and statistically investigated the correlation between fruit-eating animals and the arrangement of the fruit capsules (whether they are cauliflorous or not). Their results showed no correlation. On the other hand, they found a correlation with flowering period, nutritional status, and habitat preference.

I'm not sure if the same thing applies to the subgenus Urostiguma, which includes both the banyan tree and the Ficus microcarpa, but it might not be that simple.

Nevertheless, the fact that their fruits are cauliflorous was a very important factor in supporting the survival of many species of fruit bats.

References

Azuma, H., Harrison, RD, Nakamura, K., & Su, ZH 2010. Molecular phylogenies of figs and fig-pollinating wasps in the Ryukyu and Bonin (Ogasawara) islands, Japan. Genes & Genetic Systems 85(3): 177-192. https://doi.org/10.1266/ggs.85.177

Higashi, Koji; Su, Zhihui; and Nakamura, Keiko. 2003. Co-evolution of the genus Ficus and fig wasps. Mathematical Sciences 479: 78-83. ISSN: 0386-2240, https://www.saiensu.co.jp/search/?isbn=4910054690538&y=2003

Borges, RM 2021. Interactions between figs and gall-inducing fig wasps: adaptations, constraints, and unanswered questions. Frontiers in Ecology and Evolution 9: 685542. https://doi.org/10.3389/fevo.2021.685542

Harrison, RD, Rønsted, N., Xu, L., Rasplus, JY, & Cruaud, A. 2012. Evolution of fruit traits in Ficus subgenus Sycomorus (Moraceae): to what extent do frugivores determine seed dispersal mode?. PloS One 7(6): e38432. https://doi.org/10.1371/journal.pone.0038432

Hayashi, Masayuki. 2014. 1100 Tree Leaves Identified Through Real-Life Scans. Yama-kei Publishers, Tokyo. 759pp. ISBN: 9784635070324

Katanoda, Itsuro & Ohno, Teruyoshi. 1999. Wildflowers of the Ryukyu Archipelago from Amami: A Gift from the Sun. Nanpo Shinsha, Kagoshima. 221pp. ISBN: 9784931376212

Maeshiro, T., Nakasuga, T., & Baba, S. 1988. On the morphology of aerial roots of Ficus microcarpa. Proceedings of the Kyushu Branch of the Japanese Forestry Society 41: 87-88. ISSN: 0919-6412, http://jfs-q.jp/kfr/41/bin090907172135009.pdf

Miyagi, Tomoaki and Takahara, Kenji. 2000. On the plants of Sueyoshi Park and the food plants of the large bat. Bulletin of the Okinawa Prefectural Museum 26: 47-84. https://okimu.jp/userfiles/files/page/museum/issue/bulletin/kiyou26/26-4.pdf

Otani, T. 2005. Characteristics of medium-sized mammals as seed dispersers of berries—mainly using Japanese macaques as an example—. Nagoya University Journal of Forest Science 24: 7-43. https://doi.org/10.18999/nagufs.24.7

Otani, T. 2006. Life history of the strangler banyan tree. Forests and Forestry of Kyushu 78: 1-3. ISSN: 1346-5686, http://www.ffpri-kys.affrc.go.jp/kysmr/data/mr78.pdf

Otani, Tatsuya. 2020. The lives of *Ficus microcarpa* and *Epipactis thunbergii* in the northernmost distribution zone. *Understanding the Forests of Shikoku* 33: 2-3. ISSN: 1348-9747, https://www.ffpri.affrc.go.jp/skk/documents/sm33.pdf

Tsuchiya, Makoto & Miyagi, Koichi. 1991. Nature Observation on Southern Islands. Tokai University Press, Tokyo. xix, 194pp. ISBN: 9784486011590

Van der Pijl, L. 1961. Ecological aspects of flower evolution. II. Zoophilous flower classes. Evolution 15(1): 44-59. https://doi.org/10.2307/2405842

Source

This article is a significantly expanded version of one included in the following book.