Adaptive genetic diversity of dominant species contributes to species co-existence and community assembly

The synthesis of evolutionary biology and community ecology aims to understand how genetic variation within one species can shape community properties and how the ecological properties of a community can drive the evolution of a species.A rarely explored aspect is whether the interaction of genetic variation and community properties depends on the species'ecological role.Here we investigated the interactions among environmental factors,species diversity,and the within-species genetic diversity of species with different ecological roles.Using high-throughput DNA sequencing,we genotyped a canopydominant tree species,Parashorea chinensis,and an understory-abundant species,Pittosporopsis kerrii,from fifteen plots in Xishuangbanna tropical seasonal rainforest and estimated their adaptive,neutral and total genetic diversity;we also surveyed species diversity and assayed key soil nutrients.Structural equation modelling revealed that soil nitrogen availability created an opposing effect in species diversity and adaptive genetic diversity of the canopy-dominant Pa.chinensis.The increased adaptive genetic diversity of Pa.chinensis led to greater species diversity by promoting co-existence.Increased species diversity reduced the adaptive genetic diversity of the dominant understory species,Pi.kerrii,which was promoted by the adaptive genetic diversity of the canopy-dominant Pa.chinensis.However,such relationships were absent when neutral genetic diversity or total genetic diversity were used in the model.Our results demonstrated the important ecological interaction between adaptive genetic diversity and species diversity,but the pattern of the interaction depends on the identity of the species.Our results highlight the significant ecological role of dominant species in competitive interactions and regulation of community structure.

Genetic diversity and differentiation follow secondary succession in a multi-species study on woody plants from subtropical China

Aims Species diversity and genetic diversity may be affected in parallel by similar environmental drivers.However,genetic diversity may also be affected independently by habitat characteristics.We aim at disentangling relationships between genetic diversity,species diversity and habitat characteristics of woody species in subtropical forest.Methods We studied 11 dominant tree and shrub species in 27 plots in Gutianshan,China,and assessed their genetic diversity(A_(r))and population differentiation(F′_(ST))with microsatellite markers.We tested if Ar and population specific F′_(ST) were correlated to local species diversity and plot characteristics.Multi-model inference and model averaging were used to determine the relative importance of each predictor.Additionally,we tested for isolation-by-distance(IBD)and isolation-by-elevation by regressing pairwise F′_(ST) against pairwise spatial and elevational distances.Important Findings Genetic diversity was not related to species diversity for any of the study species.Thus,our results do not support joint effects of habitat characteristics on these two levels of biodiversity.Instead,genetic diversity in two understory shrubs,Rhododendron simsii and Vaccinium carlesii,was affected by plot age with decreasing genetic diversity in successionally older plots.Population differentiation increased with plot age in R.simsii and Lithocarpus glaber.This shows that succession can reduce genetic diversity within,and increase genetic diversity between populations.Furthermore,we found four cases of IBD and two cases of isolation-by-elevation.The former indicates inefficient pollen and seed dispersal by animals whereas the latter might be due to phenological asynchronies.These patterns indicate that succession can affect genetic diversity without parallel effects on species diversity and that gene flow in a continuous subtropical forest can be restricted even at a local scale.

Pattern and drivers of species- genetic diversity correlation in natural forest tree communities across a biodiversity hotspot

Aims Exploring species-genetic diversity correlation(SGDC)is essential for understanding spatial patterns of diversity and the underlying mechanisms.Until now,latitudinal patterns of species diversity(SD)and genetic diversity(GD)were rarely studied simultaneously.As the freezing-tolerance hypothesis predicts a decrease of SD from low to high latitudes and the central-marginal hypothesis predicts a unimodal pattern of GD along latitude,we hypothesized that SD and GD are uncorrelated.We also tested how climatic and edaphic factors affect the correlation between the two levels of biodiversity.Methods We measured(i)SD(species richness and Simpson’s diversity index)and community dissimilarity of woody plants(63 plots),(ii)GD(al-lelic richness and expected heterozygosity)and genetic differen-tiation of a dominant tree species(Euptelea pleiospermum;678 individuals from 21 populations)using nuclear microsatellite data,and(iii)climatic(annual mean precipitation,annual mean tempera-ture,minimum temperature,maximum temperature,annual rela-tive moisture,solar radiation,photosynthetically active radiation)and edaphic(total C,total N,total P,available P,K,Ca,Mg,Al,Fe,Mn,Ni,Zn,B,Mo,Cu,pH)variables of 21 sites.We conducted both linear and quadratic regression analyses of diversity param-eters against latitude.Relationships between SD and GD were tested using Pearson’s correlation.Pearson’s and Spearman’sρcor-relation coefficients were calculated between diversity parameters and environmental variables.We used stepwise multiple regression analysis to identify the significant environmental predictors of SD and GD.Important Findings We observed no significant correlation between measures of SD and GD.SD decreases with increasing latitude,which can be partly explained by the freezing-tolerance hypothesis,whereas GD pre-sents a unimodal pattern along the latitudinal gradient,which is consistent with the prediction of the central-marginal hypothesis.The contrasting latitudinal patterns of SD and GD indicate that the two levels of biodiversity do not co-vary in space.Based on both correlation analysis and stepwise multiple regression analysis,SD is only related to climatic variables,whereas GD is mainly related to edaphic variables.Our results show that different geographical and environmental factors affect SD and GD,driving the non-significant correlation between the two fundamental levels of biodiversity.Furthermore,a significantly positive correlation was observed be-tween genetic distance and community dissimilarity,both of which were significantly correlated with geographical distance.