DNA sequence variation at the hypervariable 5′ end of the mitochondrial control region was examined in 247 individuals to detect genetic divergence among 14 populations of red grouse (Lagopus lagopus scoticus) in northeastern Scotland. Ten haplotypes were resolved, several of which were shared among populations. Analysis of molecular variance, Nei's γST, and a cladistic estimate of the amount of gene flow indicated a lack of overall population differentiation. Patterns of overall panmixia are in stark contrast to previous reports of localized subdivision among the same set of populations detected using hypervariable microsatellite markers. Because grouse cocks are territorial and show extreme natal philopatry and females are the dispersing sex, such discordance could be explained by sex-biased dispersal, with extensive female-mediated gene flow preventing mitochondrial DNA divergence. However, it is difficult to reconcile how effective dispersal of females would not homogenize both mitochondrial and nuclear structure simultaneously. We use a model that examines the spatial and temporal dynamics of diparentally and uniparentally inherited genes to show that, under realistic ecological scenarios and with specific differences in the dispersal of males and females, the local effective size of the nuclear genome can be less than that of the mitochondrial and the patterns of structuring we observe are meaningful.
Corresponding Editor: J. Neigel