| Summary: | This thesis describes the global molecular population structure of two shorebird species, in particular of the dunlin, Calidris alpina, by means of comparative sequence analysis of the most variable part of the mitochondrial DNA (mtDNA) genome. There are several reasons why mtDNA is the molecule of choice to probe the recent evolutionary history of a species. Most importantly, mtDNA accumulates substitutions at a high average rate that permits the tracing of genealogies within the time frame of speciation. The population structure of shorebirds, like that of arctic- breeding waterfowl (Ploeger, 1968), must have been influenced dramatically by the Pleistocene glaciations (mainly during the last one million years). The fastest evolving part of the mtDNA genome, the non-coding control region, offers sufficient genetic resolution to reveal differentiation of such recent origin. The typical mode of maternal inheritance, the absence of recombination, and the presumed neutrality of substitutions, are characteristics that add to the suitability of mtDNA for the construction of robust phylogenies ( Chapter 1 ).Cloning and sequencing of the control region of a turnstone ( Arenaria interpres ) facilitated subsequent amplification and direct sequencing of the homologous region in other turnstones, and dunlins as well. Comparison of this approximately 1200 basepairs (bp) region for several turnstones, dunlins and a chicken ( Gallusdomesticus ) revealed the presence of differentially evolving sequence blocks within the control region. Both shorebird species contain an AC repetitive sequence at the 3' end of the light strand, varying in size (around 100 bp) and composition between individuals. Sequence identity is highest in the central part of the control region, similar to the conservation of this part in other vertebrate species. Most single nucleotide substitutions, as well as insertions and deletions, are restricted to two segments, notably at the beginning and near the end of the control region. Overall, the organization ...
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