Camel crickets carry seeds

Heterotrophic plants can often be found on the forest floor. Down there, in the dark, where the wind seldom reaches, common methods of seed dispersal stop working. But new research by Professor Kenji Suetsugu (@tugutuguk) of Kobe University shows that heterotophic plants have evolved a novel solution, in the form of camel crickets (Tachycines elegantissima).

Heterotrophic plants, which extract the energy they require for growth from other plants, rather than photosynthesis, tend to grow in shady places. Sheltered below the canopy, there isn’t enough wind to blow the dust-like seeds away from the plant, and so these strange, pale plants have enlisted some extra help to spread their seed into new territories.

Image: (a–c) Flowering plants of three species of heterotrophic plants included in the study: (a) Yoania amagiensis, (b) Monotropastrum humile, (c) Phacellanthus tubiflorus. (d–f) Fruiting plants of three species of heterotrophic plants investigated here: (d) Y. amagiensis, (e) M. humile, (f) P. tubiflorus.
(a–c) Flowering plants of three species of heterotrophic plants included in the study: (a) Yoania amagiensis, (b) Monotropastrum humile, (c) Phacellanthus tubiflorus. (d–f) Fruiting plants of three species of heterotrophic plants investigated here: (d) Y. amagiensis, (e) M. humile, (f) P. tubiflorus.

Kenji thought animals might be involved. Many plants develop bright fruits with fleshy, nutritious pulp to attract animals which, after eating the fruits, deposit the seeds with a helping of fertiliser in the form of their feaces. Most of the time, birds and mammals are the main carriers of seeds. So Kenji set up camera traps in a woodland near Fujinomia City, Japan, and waited.

After over 90 hours of observation, much of it at night, Kenji had found some surprising results. While the plants were being visited by mice, they weren’t really interested in the pale fleshy fruits. It was the crickets that caught Kenji’s attention.

Image: (a) Tachycines elegantissima feeding on Yoania amagiensis fruit. (b) Tachycines elegantissima feeding on Monotropastrum humile fruit. (c) Diestrammena japonica feeding on Phacellanthus tubiflorus fruit.
(a) Tachycines elegantissima feeding on Yoania amagiensis fruit. (b) Tachycines elegantissima feeding on Monotropastrum humile fruit. (c) Diestrammena japonica feeding on Phacellanthus tubiflorus fruit.

The camel crickets were the most frequent visitors of the plants, and they were eating the fruits. Kenji captured some of the crickets after they had fed and found the seeds in the faeces – evidence that the insects have an important role to play in carrying the seeds to new territories.

Heterotrophic plants don’t photosynthesise and rely on acquiring nutrients from other plants; they don’t have the resources to produce brightly coloured, showy fruits, or particularly large seeds. The tiny, dust-like seeds that they produce are well suited to the digestive tract of insects like the camel cricket. The three plants that Kenji studied belong to distinct and distantly related plant groups which, he suggests, shows that they evolved to entrust insects with their seeds separately.

Quitting photosynthesis, as Kenji puts it, is a big deal in the plant world, and plants have to evolve creative ways to deal with the relative lack of energy. This new study suggests that the associated effects on the ecology of other organisms that also dwell in the dark, below the canopy, may be much greater than previously thought.

Read the paper: Suetsugu, K. (2017) Independent recruitment of a novel seed dispersal system by camel crickets in achlorophyllous plantsNew Phytologist. doi: 10.1111/nph.14859

Read the press release in Japanese or in English.

Mike Whitfield (@mgwhitfield)
Development Coordinator
New Phytologist

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