Genetic differentiation within and between bird populations : taxonomic and phylogeographic implications
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AbstractThe mapping of genealogical relationships between individuals, populations, subspecies and species is important for studies of evolutionary processes and biodiversity, and for conservation decisions. In this thesis, I have used several different types of molecular markers to investigate neutral genetic variation and structure at the population, subspecies and species level in three bird species or species complexes distributed in arctic and temperate regions; snowy owl (Bubo scandiacus), dunlin (Calidris alpina) and redpoll (Carduelis flammea,C. cabaret,C. hornemanni). In addition to providing knowledge on evolutionary processes shaping genetic patterns, the analyses have implications for conservational decisions for the studied species living in the arctic environment where climatic changes may have severe impacts. I found low levels of genetic structure in all investigated groups. Snowy owls from three well separated geographic regions were analyzed with two mtDNA genes and two Z-chromosome introns and they seemed to constitute one panmictic population. The species was also relatively genetically diverse compared to three other owl species breeding in temperate regions. The pattern found with four genetic markers (mtDNA control region, a Z-chromosome intron, microsatellites and AFLPs) among dunlin populations in Western Palearctic and East Greenland did not correspond to the four subspecies recognized in the area. Rather, dunlins in this area form two genetically monophyletic groups that are geographically overlapping, and the resulting pattern is isolation by distance. Declining and fragmented dunlin populations of the subspecies southern dunlin (C. a. schinzii) were not genetically deprived compared to vital populations in more continuous habitats. Nor was the isolated dunlin population on Svalbard, this population was genetically similar to populations on East Greenland, Iceland and around the Baltic Sea. The three redpoll species were exceptionally little differentiated in mtDNA control region sequences and microsatellites. The low level of genetic structure in dunlins and redpolls is surprising considering their taxonomic status. Recent divergence of morphological characters or ongoing gene flow may explain the patterns found in both species. I suggest that the clinal variation described illustrates a more common pattern than is normally acknowledged in avian systematics, and that conservation politics may benefit from taking these patterns into consideration instead of being constrained to categorical thinking. This is important in today’s situation of declining population sizes and threatened species in an increasing number of areas and habitats.
List of papers
I Marthinsen, G., Wennerberg, L., Solheim, R. and Lifjeld, J. T.: Indication of one panmictic population of snowy owls (Bubo scandiacus) Manuscript
II Marthinsen, G., Wennerberg, L. and Lifjeld, J. T.: Phylogeography and subspecies taxonomy of dunlins (Calidris alpina) in western Palearctic analyzed by DNA microsatellites and AFLP markers. Biological Journal of the Linnean Society. In press.
III Wennerberg, L., Marthinsen, G. and Lifjeld, J. T.: Conservation genetics and phylogeography of Southern dunlins Calidris alpina schinzii.Submitted manuscript
IV Marthinsen, G., Wennerberg, L., Pierce, E. and Lifjeld, J. T.: Phylogeography and genetic diversity of dunlins Calidris alpina in Svalbard Manuscript
V Marthinsen, G., Wennerberg, L. and Lifjeld, J. T.: Low genetic support for separate redpoll species (Carduelis flammea – hornemanni – cabaret) with mtDNA control region sequences and microsatellite markers Submitted manuscript