Discovery Magazine

Photo Credit: Carrie Topp

Evolution of endemism in Commander and Aleutian Island Birds

How biodiversity is generated and maintained are central questions in evolutionary biology and conservation biology. Pleistocene glacial cycles are thought to have shaped species assemblages at high latitudes, but the role that refugial isolation and post-glacial colonization played in generating biodiversity is uncertain. We have been studying the population genetics of birds in the Aleutian Islands, Alaska (and to a limited extent in the Commander Islands, Russia), where there are many endemic subspecies. Based on our research, we have developed several hypotheses about biodiversity formation and conservation in this region, including: 1) the Commander Islands served as a refugium for birds (such as Rock Ptarmigan, Common Raven and Pacific Wren) during the late Pleistocene glacial cycles; 2) genetically divergent lineages found in the western Aleutian Islands, such as the Common Raven, are endemic and thus represent separate conservation units; and 3) birds colonized the Aleutian Islands from North America rather than from Asia.

We currently have some support for these hypotheses, but to fully test these ideas we need to travel to the Commander Islands and the Kamchatka Peninsula of Russia to obtain specimens of several species, including Common Raven, Rock Ptarmigan, Pacific Wren, and Rock Sandpiper. We will use next-generation sequencing to provide genome-scale sequence data using a RAD-tag approach to identify and genotype single nucleotide polymorphisms (SNPs) in each individual. By using this method we will be able to acquire a multi-locus data set for non-model organisms (such as Common Raven, Rock Ptarmigan, and Pacific Wren) that will provide substantially more information about the evolutionary relationships among Aleutian and Commander Island birds. By testing these hypotheses, we seek to fully describe the patterns and discover the processes responsible for endemism among these remote islands.