Genetic And Functional Leaf Trait Diversity Throughout The Distribution Of Two Cerrado Tree Species: Testing The Centre-Periphery Hypothesis

Aim The centre-periphery hypothesis (CPH) states that peripheral populations exhibit lower genetic diversity, abundance and size, and higher differentiation compared to central populations, due to a decline in environmental suitability towards range margins. Here, we tested if neutral genetic diversity and functional leaf trait diversity fit the predicted patterns of the CPH.Location Cerrado, Brazil.Taxon Qualea grandiflora (Vochysiaceae) and Annona crassiflora (Annonaceae).Methods Variation in eight functional leaf traits and nine or eight microsatellite loci were analysed in 37 populations (777 individuals) of Q. grandiflora and 21 populations (397 individuals) of A. crassiflora. We tested CPH using three distinct centres of species' range: geographical (centre of species' geographic occurrence), historical (centre of species' refugia) and ecological (centre of species' current suitability areas). Generalised linear regressions were performed between genetic diversity and differentiation, coefficients of variation and means of leaf metamer traits of populations and their distances from each centre.Results A decrease in allele richness was observed from central towards peripheral populations for ecological (both species) and geographical centres (Q. grandiflora). Overall, the results for both species pointed to a decrease in metamer vigour towards marginal populations, pattern consistent with a decrease in environmental suitability towards periphery as predicted by CPH. Besides geographical and ecological centres, leaf traits fitted CPH considering historical centre.Main Conclusions Results for leaf traits and genetic diversity of two phylogenetically distant species indicate the consistency of the CPH for Cerrado species. Our results highlight the importance of considering distinct centres and a great number of populations along species' range to better determinate the processes underlying the distribution of genetic diversity and functional traits. The low genetic diversity and metamer vigour in marginal populations can explain the Cerrado endemism of studied species and suggest that the ongoing climatic changes can be critical for their survival.