Limited differentiation in microsatellite DNA variation among northern populations of the yellow warbler: evidence for male-biased gene flow?

Comparisons of the patterns of differentiation among genetic markers with different modes of inheritance can provide insights into patterns of sex-biased dispersal and gene flow. Here, we compare the patterns of differentiation in six microsatellite loci among eight northern breeding populations of the yellow warbler (Dendroica petechia) with results obtained with mitochondrial DNA. Significant but low levels of differentiation (overall FST = 0.014; overall RST = 0.015) were present across all populations. The level of differentiation is substantially less than that observed in the same samples based on mitochondrial DNA control region variation. The presence of low population imbalance index values and significant isolation-by-distance relationships for both FST and RST suggests that these populations are at evolutionary equilibrium and that the high degree of similarity between populations may be due to high levels of male-biased gene flow. This suggests that there may be significant but previously unappreciated differences in the long-distance and/or episodic dispersal behaviour of males and females in these birds.