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 d ifferent modes of inheritance fan provide insights into patterns of sex-bia sed dispersal and gene flow. Here, we compare the patterns of differentiati on in six microsatellite loci among eight northern breeding populations of the yellow warbler (Dendroica petechia) with results obtained with mitochon drial DNA. Significant but low levels of differentiation (overall F-ST = 0. 014; overall R-ST = 0.015) were present across all populations. The level o f differentiation is substantially less than that observed in the same samp les based on mitochondrial DNA control region variation. The presence of lo w population imbalance index values and significant isolation-by-distance r elationships for both F-ST and R-ST suggests that these populations are at evolutionary equilibrium and that the high degree of similarity between pop ulations may be due to high levels of male-biased gene flow. This suggests that there may be significant but previously unappreciated differences in t he long-distance and/or episodic dispersal behaviour of males and females i n these birds.