What kind of animal transports the seeds of the world's smallest fruit- bearing plants?
Novel seed dispersal system of a mushroom-like non-photosynthetic plant


Date:
August 21, 2020
Source:
Kobe University
Summary:
Balanophora have some of the smallest fruits among angiosperms,
leading researchers to question how the seeds of these plants
are dispersed. Very little is currently known about their seed
dispersal system. Researchers have now documented an unrecognized
seed dispersal mutualism between the peculiar, mushroom-like
non-photosynthetic plant Balanophora yakushimensis and its
avian visitors. The birds obtain nutrients, not from the tiny
undernourished fruits, but from the larger fleshy bracts, while
B. yakushimensis plants benefit from the seed dispersal.



FULL STORY ========================================================================== Balanophora have some of the smallest fruits among angiosperms,
leading researchers to question how the seeds of these plants are
dispersed. However, very little is currently known about their seed
dispersal system. Associate Professor SUETSUGU Kenji (Kobe University
Graduate School of Science) documents an unrecognized seed dispersal
mutualism between the peculiar, mushroom-like non-photosynthetic
plant Balanophora yakushimensis and its avian visitors. The birds
obtain nutrients, not from the tiny undernourished fruits, but from
the larger fleshy bracts, while B. yakushimensis plants benefit from
the seed dispersal. In contrast to well-studied fleshy-fruited plants,
the dry-fruited Balanophora species has adopted an avian seed dispersal mutualism through its fleshy bracts, which act as both visual attractants
and nutritional rewards.

These findings were published on 19 August, 2020 in 'Ecology'.


==========================================================================
The color green is a defining feature of the plant kingdom, and plants are mostly assumed to be autotrophs that can make their own food from simple inorganic substances such as carbon dioxide. Therefore, the biological
oddities of non-photosynthetic plants have long attracted the attention
of naturalists.

The genus Balanophora comprises partially or entirely subterranean non- photosynthetic plants with extremely reduced morphological features. Just
like the most famous parasitic plant Rafflesia, Balanophora mooch water
and nutrients off the host plants they are attached to. Consisting of
highly specialized root parasites, Balanophora is definitely one of the
most unusual plant genera.

Recent studies have suggested that the evolutionary transition to full heterotrophy is a complex process, although, superficially, it may
seem like a loss of photosynthetic ability. One of the most significant characteristics is the extreme reduction in the size and complexity of
their seeds. In fact, Balanophora infructescences contain 100,000 to
1,000,000 tiny dry fruits situated at the base of a fleshy, club-shaped transformed bracts. As Balanophora fruits are some of the smallest among angiosperms, the fundamental question arises as to what mode of seed
dispersal occurs in these plants.

Yet surprisingly, almost nothing is known about the seed dispersal system
of Balanophora, despite this being one of the most important aspects of
plant biology. Due to Balanophora infructescences being morphologically
similar to mushrooms, it had been assumed that mycophagous rodents
were its main seed dispersers. However, the lack of information about
the animals that actually feed on Balanophora fruits has prevented the elucidation of the seed dispersal system employed by the group.

Suetsugu studied the B. yakushimensis seed dispersal system in the
understory of the temperate forests on Yakushima Island, Kagoshima
Prefecture, Japan.

Consequently, he documented a previously unnoticed seed dispersal
mutualism between the dry-fruited B. yakushimensis and its avian
visitors. Even though plants have evolved various mechanisms to mediate
seed dispersal by animals, the predominant strategy is the production
of fleshy fruits with embedded seeds. However, B. yakushimensis have
adopted alternative approaches; not tiny undernourished fruits but larger fleshy bracts act as a tool to elicit seed dispersal. Since the bright
red transformed bracts are much larger than their minute fruits, they
should function as the primary visual attractants and edible rewards
for birds. Overall, the study documents a previously unrecorded seed
dispersal mutualism; avian visitors obtain nutrients from transformed
bracts, while B. yakushimensis plants benefit from seed dispersal. Further studies on the seed dispersal systems of other Balanophora members will
provide greater insights into ecology of these bizarre plants.


========================================================================== Story Source: Materials provided by Kobe_University. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Kenji Suetsugu. A specialized avian seed dispersal system in a
dry‐fruited non‐photosynthetic plant, Balanophora
yakushimensis. Ecology, 2020; DOI: 10.1002/ecy.3129 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200821094819.htm

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