title: A role for nonphysical barriers to gene flow in the diversification of a highly vagile seabird, the masked booby (Sula dactylatra).
abstract: To test the hypothesis that nonphysical barriers to gene flow play a role in the divergence of low-latitude seabird populations, we applied phylogeographic methods to mitochondrial control region sequence variation in a global sample of masked boobies (Sula dactylatra). In accord with previous studies, we found that Indo-Pacific and Atlantic haplotypes form two divergent lineages, excluding one haplotype previously attributed to secondary contact between the Indian Ocean and the Caribbean Sea. Within the Indo-Pacific and the Atlantic, we found a relatively large number of haplotypes, many of which were unique to a single population. Although haplotypes from most populations were found in more than one higher-level clade, nested clade analysis revealed a significant association between clades and geography for the majority of higher-level clades, most often interpreted as a consequence of isolation by distance. We found low levels of gene flow within Indo-Pacific and Atlantic populations, and a significant correlation between gene flow and geographical distance among Indo-Pacific populations. We estimate that Indo-Pacific masked boobies experienced rapid population growth approximately 180,000 years ago and that the majority of Indo-Pacific and Atlantic populations diverged within the last approximately 115,000 years. These combined data suggest that the predominant pattern between Indo-Pacific and Atlantic populations is long-term isolation by physical barriers to gene flow. In contrast, populations within these regions appear to have diverged despite few obvious physical barriers to gene flow, perhaps as a consequence of limited natal dispersal combined with local adaptation and/or genetic drift.
authors.affiliation: Department of Biology, Queen's University, Kingston, ON K7L 3N6, Canada. tammy.steeves@canterbury.ac.nz
authors.forename: Tammy E
authors.initials: TE
authors.lastname: Steeves
authors.forename: David J
authors.initials: DJ
authors.lastname: Anderson
authors.forename: Vicki L
authors.initials: VL
authors.lastname: Friesen
mesh_terms: D000818:Animals; D001717:Birds / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics; D051456:Gene Flow; D014644:Genetic Variation; D005843:Geography; D006239:Haplotypes; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial