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Many species have mitochondrial DNA lineages that are phylogenetically intermixed with other species, but studies have rarely tested the cause of such paraphyly. In this study, we tested two hypotheses that could explain mitochondrial paraphyly of Holarctic gadwalls (Anas strepera) with respect to Asian falcated ducks (A. falcata). First, hybridization(More)
Many studies of phylogeography, speciation, and species limits restrict their focus to a narrow issue: gene tree monophyly. However, reciprocal monophyly does not provide an ideal touchstone criterion of any aspect of evolutionary divergence. There is a continuum of divergence stages as isolated populations go from initial allele frequency differences to(More)
Hypoxia is one of the most important factors affecting survival at high altitude, and the major hemoglobin protein is a likely target of selection. We compared population genetic structure in the alphaA and betaA hemoglobin subunits (HBA2 and HBB) of five paired lowland and highland populations of Andean dabbling ducks to unlinked reference loci. In the(More)
During the Late Pleistocene, glaciers sundered many species into multiple glacial refugia where populations diverged in allopatry. Although deeply divergent mitochondrial DNA (mtDNA) lineages often reflect the number of refugia occupied, it is unlikely that populations that split during the recent Wisconsin glaciations will have reached reciprocal(More)
When populations become locally adapted to contrasting environments, alleles that have high fitness in only one environment may be quickly eliminated in populations adapted to other environments, such that gene flow is partly restricted. The stronger the selection, the more rapidly immigrant alleles of lower fitness will be eliminated from the population.(More)
More than 100 species of birds have Holarctic distributions extending across Eurasia and North America, and many of them likely achieved these distributions by recently colonizing one continent from the other. Mitochondrial DNA (mtDNA) and five nuclear introns were sequenced to test the direction and timing of colonization for a Holarctic duck, the gadwall(More)
Species-level DNA phylogenies frequently suffer from two shortcomings--gene trees usually are constructed from a single locus, and often species are represented by only one individual. To evaluate the effect of these two shortcomings, we tested phylogenetic hypotheses within the wigeons and allies, a clade of Anas ducks (Anatidae) composed of five species.(More)
A widely accepted paradigm is that sedentary Neotropical bird species are a reservoir that gives rise to temperate-tropical migratory species. Recently, an alternative theory has been proposed, that developmental plasticity can allow some individuals within a migratory species to establish a disjunct breeding range through loss of migration, thus(More)
The relevance of spatial variation in the environment and host communities for parasite community composition is poorly documented, creating a need for additional case studies from which general principles can be developed. Avian malaria in southern African waterfowl has not previously been studied. As a first step towards documenting and understanding its(More)
Genetic studies of waterfowl (Anatidae) have observed the full spectrum of mitochondrial (mt) DNA population divergence, from apparent panmixia to deep, reciprocally monophyletic lineages. Yet, these studies often found weak or no nuclear (nu) DNA structure, which was often attributed to male-biased gene flow, a common behaviour within this family. An(More)