MHC variation reflects the bottleneck histories of New Zealand passerines

Most empirical evidence suggests that balancing selection does not counter the effects of genetic drift in shaping post-bottleneck MHC genetic diversity when population declines are severe or prolonged. However, few studies have been able to include data from historical specimens, or to compare populations/species with different bottleneck histories. In this study we examined MHC class II B and microsatellite diversity in four New Zealand passerine (songbird) species that experienced moderate to very severe declines. We compared diversity from historical samples (collected circa 1884-1938) to present day populations. Using a Bayesian framework, we found that the change in genetic diversity from historical to contemporary samples was affected by three main factors: 1) whether the data were based on MHC or microsatellite markers, 2) species (as a surrogate for bottleneck severity) and 3) whether the comparison between historical and contemporary samples was made using historical samples o...