Population genetic patterns of a mangrove‐associated frog reveal its colonization history and habitat connectivity

Abstract

AbstractAimTo understand the impact of historical and contemporary habitat distributions and connectivity on the spatial patterns of a species' genetic variation and divergence, we examined the phylogenetic relationship, population genetic structure and demographic history of a mangrove‐specialist, the crab‐eating frog (Fejervarya cancrivora) from 10 geographic populations in China and northern Vietnam.LocationSoutheast Asian coasts, especially the southern China and northern Vietnam coasts.MethodsWe used the sequences of three mitochondrial DNA (mtDNA) regions to infer phylogenetic relationships and divergence times between our samples and those from other Southeast Asian countries. Thirteen nuclear microsatellite loci were used to analyse population genetic structure. Ancient and more recent demographic history was assessed using mtDNA and microsatellite data, respectively, and population divergence history scenarios were evaluated using approximate Bayesian computation.ResultsThe mtDNA haplotypes from China joined the F. cancrivora clades from the Philippines, Thailand and Bangladesh, which diverged from the clades from Malaysia and Indonesia. Microsatellite analyses revealed three genetically differentiated clusters and a strong pattern of isolation by distance at the individual level. Ancient population sizes were relatively stable, but genetic signatures of recent population declines were detected. Population divergence history analyses supported that Hainan populations were ancestral to those of the Guangdong, Guangxi and northern Vietnam populations.Main conclusionsOur results suggest that F. cancrivora's contemporary genetic patterns have been shaped by past and present habitat conformations. This species may have dispersed along the coast from Southeast Asia to China during Pleistocene glaciations when sea levels were low, colonizing the Hainan area first. It subsequently spread to mainland China coasts when sea levels rose and shorelines withdrew. Additionally, current declines and fragmentation of mangrove forests have likely exacerbated population reductions and genetic divergences among now disjunct populations. This study provides a framework for understanding the population history of mangrove‐associated biota and thus aids conservation management of this critical ecosystem.