Tropical forest communities are among the most diverse on Earth. A few large genera tend to make disproportionate contributions to this diversity. How a large number of congeneric species coexist in local communities has been a puzzle in community ecology research.
In a study published in Journal of Ecology, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and their collaborators tried to explore the co-occurrence mechanism of closely related species. They investigated 13 species of Ficus that occur within a 20-ha forest dynamics plot using spatially explicit soil data and species-level transcriptomic data.
The researchers utilized detailed data on the functional genetic similarity of species to assess whether co-occurring congeners are dissimilar in drought and defence-related genes. Specifically, they sequenced and assembled the leaf transcriptomes of 13 locally co-occurring Ficus in a tropical rainforest in southwest China and used the data to quantify whether genetic distance between species in genes related to drought and defence were linked to patterns of co-occurrence within and between habitats varying in their soil water content.
They found widespread and consistent evidence of the importance of defence gene dissimilarity in co-occurring species, providing genetic support for what would be expected under the Janzen-Connell mechanism. They also found that drought-related gene sequence similarity is related to Ficus co-occurrence, indicating that similar responses to drought promote co-occurrence.The differences in defense genes of co-occurring Ficus trees were associated with the co-occurrence of Ficus, while the similarities in drought-related gene sequences were associated with the co-occurrence of Ficus.
"Our study provides the first detailed functional genomic evidence that, taking Ficus as an example, the co-occurrence of closely related species may be related to functional gene differentiation in terms of drought and defense. The results also confirmed the potential of community transcriptomics in helping to explore mechanisms underlying biodiversity maintenance," said YANG Jie of XTBG.
 

Contact
YANG Jie Ph.D Principal Investigator
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
E-mail: yangjie@xtbg.org.cn
First published: 12 January 2024