Dominant species determine the pattern of correlation between species and genetic diversity in the rainforest
Species diversity can be causally influenced by the genetic diversity of a dominant species. As tropical forests have a very high diversity of species, it is not clear whether the model of correlation between species and genetic diversity (SGDC) depends on the ecological role of focal species.
In a study published in Plant Diversity, researchers at the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences attempted to reveal the underlying mechanisms of species coexistence in species-rich communities. They found that the adaptive genetic diversity of dominant species contributes to species coexistence and community assembly.
The researchers used high-throughput DNA sequencing to derive the adaptive, neutral, and total genetic diversity of two coexisting tree species, a canopy-dominant tree species, Parashorea chinensis, and an abundant tree species in understory, Pittosporopsis kerrii, which can shape the community characteristics of the seasonal rainforest of Xishuangbanna.
They also quantified the correlation patterns between species and the genetic diversity of both species and community species.
Using structural equation modeling (SEM), the researchers further deciphered the hierarchical relationships between genetic and species diversity of the two species and environmental variables.
The study showed that the adaptive genetic diversity of the dominant understory species, Pi. Kerrii, and the species richness of rarefied trees were negatively correlated, but that there was no significant correlation between adaptive genetic diversity of the canopy dominant species Pa. chinensis, the largest biomass in the community.
The SEM analysis revealed that the two levels of biodiversity were causally related, as increasing adaptive genetic diversity resulted in increased species diversity by promoting coexistence.
The availability of nitrogen in the soil was the main driver of the observed correlations between species and genetic diversity. The availability of soil nitrogen has played an important role in the structuring of species diversity and the adaptive genetic diversity of dominant canopy species.
“Our results reveal the important ecological role of dominant species in competitive interactions and the regulation of community structure, and they highlight the important ecological link between genetic diversity and species diversity,” said Dr LI Qiaoming, first author of the study.