Gene flow maintains genetic diversity and colonization potential in recently range-expanded populations of an oriental bird, the light-vented bulbul (pycnonotus sinensis, aves: Pycnonotidae)

Aim: Two alternative genetic patterns are typical in recently established populations. One is reduced genetic diversity but significant population structuring compared with original populations. The other is the persistence of genetic polymorphisms and the lack of differentiation in frontier populations. This study aims to test for these patterns by examining population genetics of the Light-vented Bulbul (Pycnonotus sinensis), an Oriental bird that has been undergoing rapid range expansion. Location: Eastern China. Methods: Molecular analyses were conducted on mitochondrial DNA and microsatellite datasets from 256 individuals. Intraspecific phylogeny was reconstructed by Bayesian inference and network analysis. Analysis of molecular variance (AMOVA) and Bayesian clustering were applied to determine population structure. Genetic diversity was tested to determine whether there were significant differences between frontier and source populations. Population expansions were tested in mtDNA and microsatellites. Gene flow and recent migrants were estimated by Bayesian methods. Results: Both high- and low-nucleotide diversities were recorded in frontier populations, and differences in genetic diversity between frontier and source populations were not statistically significant. Population differentiation was recorded in some source but not in frontier populations. Population size expansion was detected both in frontier and in source populations, and for the whole dataset, commencing before the Last Glacial Maximum. Main conclusions: Genetic diversity can be maintained in expanding populations of the Light-vented Bulbul, and genetic differentiation can be avoided, where substantial genetic exchanges are occurring. This study also discusses the potential effects of evolutionary properties such as historical population growth on recently recorded range expansion.