Habitat divergence, reproductive phenology divergence and leaf functional traits divergence among three closely related congeneric plant species, the endemic Helicia rengetiensis and widespread H. formosana and H. cochinchinensis

Background/Question/Methods

Woody plant species coexist in the face of intense competition for recourse remains a fundamental challenge to community ecology. Sympatric congeneric coexistence of species is a remarkable feature which caused high alpha diversity in the tropical forest. Three congeneric subcanopy tree species, Helicia formosana, Helicia rengetiensis and Helicia cochinchinensis coexist in the subtropical forest in Taiwan. In this study, environmental factors, leaf functional traits and reproductive phenology were surveyed in order to understand the coexistence of three species in Taiwan Island scale and the 25-ha forest dynamics plot scale. We hypothesized 1. Habitat divergence affected the distribution of three congerneric species, and it also caused leaf functional traits divergence, 2. If habitat of congeneric species converged their reproductive phenology should diverge in order to prevent competition. Canonical Correspondence Analysis (CCA) was used to know environmental factors that effect distribution of three species and torus translation test was used to test the habitat association of three species. For testing the reproductive phenology divergence, one way analysis of variance (ANOVA) was used to know the differences in peak flowering time and fruiting time among three species, and Duncan’s significance tests for pairwise were used to determine whether the peak flowering time and fruiting time was significantly different from zero for other two species. Effects of habitat and species on leaf traits were analysed using two-way ANOVA. Duncan’s significance tests for pairwise were used to compare the leaf traits among three Helicia species in different habitats.

Results/Conclusions

The CCA results showed environmental factors explained 14.4% and 63.1% variations for Taiwan Island scale and 25-ha plot scale, respectively. Torus translation test showed H. formosana and H. cochinchinensis preferred the similar habitat, but H. rengetiensis preferred the different habitat. Our results supported habitat divergence affected distributions of Helicia formosana and Helicia rengetiensis, and which also caused divergence of leaf functional traits. Habitat converged species, their peak flowering time showed divergence, but their fruiting time showed no divergence. Our results concluded environmental factors affected the distribution of species and divergent of leaf functional traits. Meanwhile, we also suggested if habitats of congeneric species overlap, divergence of flowering time might reduce species competition for shared pollinators and thereby facilitate species coexistence.