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.

Opposing intraspecific vs.interspecific diversity effects on herbivory and growth in subtropical experimental tree assemblages

Aims Positive plant diversity-ecosystem function relations are ultimately driven by variation in functional traits among individuals that form a community.To date,research has largely focused on the role of species diversity for ecosystem functioning.However,substantial intraspecific trait variation is common and a significant part of this variation caused by genetic differences among individuals.Here,we studied the relative importance of species diversity and seed family(SF)diversity within species for growth and herbivory in experimental subtropical tree assemblages.Methods In 2010,we set up a field experiment in subtropical China,using four species from the local species pool.Trees were raised from seeds,with seeds from the same mother tree forming an SF.We established 23 plots containing one or four species(species diversity treatment)and one or four SFs per species(SF diversity treatment).Tree growth(stem diameter,plant height and crown expansion)and herbivory(percentage leaf loss due to leaf chewers)were monitored annually from 2011 to 2013.Important findings Tree species richness promoted growth but had no effect on herbivory.In contrast,SF diversity reduced growth and increased herbivory but only so in species mixtures.Most of the observed effects were time dependent,with the largest effect found in 2013.Our results suggest that biodiversity can affect plant performance directly via tree species-species interactions,or context dependent,via potential effects on inter-trophic interactions.Two important conclusions should be drawn from our findings.Firstly,in future studies regarding biodiversity and ecosystem functioning(BEF)relationships,intraspecific genetic diversity should be given similar weight as species diversity as it has often been neglected and its effects are not well understood.Secondly,we demonstrate opposite effects of biodiversity among and within species,stressing the importance to consider the effects of multiple levels of biodiversity simultaneously.