Ants and camel crickets serve dual roles in both pollinating and dispersing seeds of Balanophora subcupularis, as discovered by Kobe University, providing crucial insights into plant-insect interactions and conservation.
The dark and damp understories of the subtropical forests on Shimoshima Island in Japan are home to parasitic plants called Balanophora, which feed on the roots of other plants. For over a century, the mechanism of their seed dispersal has remained a mystery.
Although it has been suggested that the tiny seeds are carried by the wind, the understories of these (sub)tropical forests experience little to no wind. Some plant species among the Balanophora are bright red, resembling strawberries, and attract birds and rabbits to eat and thus disperse the seeds.
However, others, like Balanophora subcupularis, have dull colors and a yeasty smell, making it unlikely that vertebrates are involved. Similarly, the mechanism of the plant’s pollination has remained unclear.
Research Methods and Discoveries
The Kobe University botanist Suetsugu Kenji specializes in understanding the interactions between these parasitic plants and their surrounding ecosystems, including the often overlooked but crucial role of invertebrate pollinators and seed dispersers.
To determine who aids B. subcupularis in its reproduction, he and his team watched the plants for over 100 hours and took tens of thousands of automated night photographs while the flower was in bloom or bore fruit, identifying the visitors. In addition, they conducted both animal exclusion and seed feeding experiments to ascertain whether the animals in the photographs are indeed effective pollinators and seed dispersers.
Significance of Dual Roles in Pollination and Seed Dispersal
In two consecutive papers published in the journal Ecology, the Kobe University team published that B. subcupularis is pollinated by ants and camel crickets, which visit the plants for their pollen and nectar. Remarkably, these same species also later feed on the fleshy leaves carrying the seeds, aiding in seed dispersal.
“It is well known that many plants rely on insects for pollination, although it’s rare for ants and crickets. Also, many plants use birds and mammals to distribute their fruits, and again it’s very unusual that crickets or other tiny arthropods take over this role. Even more striking, it is very rare for the same animal to perform both functions, and it is unique that the same invertebrates do so,” says Suetsugu on his surprise about this finding.
The Kobe University botanist suggests that this rare combination of pollination and seed distribution roles may be influenced by two factors. First, “B. subcupularis blooms late in the year when many typical pollinators, such as bees, are less active. In addition, our study site is a small island at the northern edge of the plant’s distribution, which might contribute to the scarcity of pollinators and seed dispersers.”
Implications for Conservation and Plant Survival
Suetsugu also highlights the broader implications of these findings: “This underscores the importance of invertebrates in plant reproduction and encourages us to look deeper into how these relationships evolve and what environmental factors drive such unique adaptations. More practically, our findings also contribute to conservation strategies for rare and endangered plants like Balanophora subcupularis. Understanding their reliance on specific invertebrates for both pollination and seed dispersal helps inform habitat preservation efforts and the management of invertebrate populations, which are crucial for these plants’ survival.”
References:
“Ants, camel crickets, and cockroaches as pollinators: The unsung heroes of a non-photosynthetic plant” by Kenji Suetsugu and Hiromu Hashiwaki, 4 December 2024, Ecology.
DOI: 10.1002/ecy.4464
“Beyond pollination: Ants and camel crickets as double mutualists in a non-photosynthetic plant” by Kenji Suetsugu and Hiromu Hashiwaki, 4 December 2024, Ecology.
DOI: 10.1002/ecy.4465
This research was funded by the Japan Science and Technology Agency (grant JPMJPR21D6).
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