title: Phylogeography and genetic structure of two Patagonian shag species (Aves: Phalacrocoracidae).
abstract: We compared the phylogeographic and genetic structure of two sympatric shag species, Phalacrocorax magellanicus (rock shag) and Phalacrocorax atriceps (imperial shag), from Patagonia (southern South America). We used multilocus genotypes of nuclear DNA (microsatellite loci) from 324 individuals and mitochondrial DNA sequences (ATPase) from 177 individuals, to evaluate hypotheses related to the effect of physical and non-physical barriers on seabird evolution. Despite sharing many ecological traits, the focal species strongly differ in two key aspects: P. magellanicus has a strong tendency to remain at/near their breeding colonies during foraging trips and the non-breeding season, while P. atriceps exhibits the converse pattern. Both species showed similar mtDNA genetic structure, where colonies from the Atlantic Coast, Pacific Coast and Fuegian region were genetically divergent. We also found similarities in the results of Bayesian clustering analysis of microsatellites, with both species having four clusters. However population differentiation (e.g. Fst, Φst) was higher in P. magellanicus compared to P. atriceps, and average membership probabilities of individuals to specific clusters (Q-values) were also higher in the former. Phalacrocorax magellanicus has strong phylogeographic structure, consistent with the impact of Pleistocene glaciations, with diagnostic haplotypes associated with each of the three mentioned regions. The same pattern was not as evident for P. atriceps. Migration rate estimators were higher for P. atriceps than for P. magellanicus; however both species followed an n-island-like model of gene flow, this implies that dispersal occurs across the continental land mass that separates Atlantic and Pacific Oceans. Our results supported the hypothesis that non-physical barriers are important drivers of the genetic and phylogeographic structure in seabirds, and also that physical barriers constitute effective but not absolute impediments to gene flow.
authors.affiliation: Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", CONICET, Av. Angel Gallardo 470, C1405DJR Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina. Electronic address: lucianocalderon@yahoo.com.ar.
authors.forename: Luciano
authors.initials: L
authors.lastname: Calderón
authors.affiliation: Biología y Manejo de Recursos Acuáticos, Centro Nacional Patagónico, CONICET, Blvd. Brown 2915, U9120ACD Puerto Madryn, Chubut, Argentina; Wildlife Conservation Society, Amenabar 1595, C1426AKC Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Flavio
authors.initials: F
authors.lastname: Quintana
authors.affiliation: Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", CONICET, Av. Angel Gallardo 470, C1405DJR Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Gustavo S
authors.initials: GS
authors.lastname: Cabanne
authors.affiliation: Queen's University, Department of Biology, Kingston, Ontario K7L3N6, Canada.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Lougheed
authors.affiliation: Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", CONICET, Av. Angel Gallardo 470, C1405DJR Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Pablo L
authors.initials: PL
authors.lastname: Tubaro
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D001717:Birds / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics; D006801:Humans; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D010802:Phylogeny; D058974:Phylogeography; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial
keywords: Gene flow; Genetic structure; Non-physical barriers; Phylogeography; Physical barriers; Seabirds