Historic DNA reveals contemporary population structure results from anthropogenic effects, not pre-fragmentation patterns
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- Tracy, L.N. & Jamieson, I.G. Conserv Genet (2011) 12: 517. doi:10.1007/s10592-010-0158-9
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Contemporary patterns of genetic structure among fragmented populations can either result from historic patterns or arise from human-induced fragmentation. Use of historic samples collected prior to fragmentation allows for the origin of genetic structure to be established and appropriate management steps to be determined. In this study, we compare historic and contemporary levels of genetic diversity and structure of an endangered passerine, the New Zealand mohua or yellowhead (Mohoua ochrocephala), using nuclear microsatellites. We found that a significant amount of allelic richness has been lost over the last 100 years. Close to half of this was due to extinction of birds from entire regions, but almost as much was due to loss of genetic diversity within extant populations. We found a pattern of isolation by distance among contemporary populations, which could have resulted from historic structure due to limited gene flow along a latitudinal cline. However, we found that minimal genetic structure existed historically. The pattern of increased structure over time was confirmed by factorial correspondence analysis. We conclude that the genetic structure apparent today resulted from anthropogenic effects of recent fragmentation and isolation. We emphasize the importance of assessing genetic structure of populations prior to their fragmentation, when determining the significance of contemporary patterns. This study highlights the growing importance of museum specimens as a tool in the conservation of threatened and endangered species.