title: Population structure and phylogeography reveal pathways of colonization by a migratory marine reptile (Chelonia mydas) in the central and eastern Pacific.
abstract: Climate, behavior, ecology, and oceanography shape patterns of biodiversity in marine faunas in the absence of obvious geographic barriers. Marine turtles are an example of highly migratory creatures with deep evolutionary lineages and complex life histories that span both terrestrial and marine environments. Previous studies have focused on the deep isolation of evolutionary lineages (>3 mya) through vicariance; however, little attention has been given to the pathways of colonization of the eastern Pacific and the processes that have shaped diversity within the most recent evolutionary time. We sequenced 770 bp of the mtDNA control region to examine the stock structure and phylogeography of 545 green turtles from eight different rookeries in the central and eastern Pacific. We found significant differentiation between the geographically separated nesting populations and identified five distinct stocks (F ST = 0.08-0.44, P < 0.005). Central and eastern Pacific Chelonia mydas form a monophyletic group containing 3 subclades, with Hawaii more closely related to the eastern Pacific than western Pacific populations. The split between sampled central/eastern and western Pacific haplotypes was estimated at around 0.34 mya, suggesting that the Pacific region west of Hawaii has been a more formidable barrier to gene flow in C. mydas than the East Pacific Barrier. Our results suggest that the eastern Pacific was colonized from the western Pacific via the Central North Pacific and that the Revillagigedos Islands provided a stepping-stone for radiation of green turtles from the Hawaiian Archipelago to the eastern Pacific. Our results fit with a broader paradigm that has been described for marine biodiversity, where oceanic islands, such as Hawaii and Revillagigedo, rather than being peripheral evolutionary "graveyards", serve as sources and recipients of diversity and provide a mechanism for further radiation.
authors.affiliation: Marine Mammal & Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration 8901 La Jolla Shores Drive, La Jolla, California, 92037.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Dutton
authors.affiliation: Marine Mammal & Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration 8901 La Jolla Shores Drive, La Jolla, California, 92037.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Jensen
authors.affiliation: Marine Mammal & Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration 8901 La Jolla Shores Drive, La Jolla, California, 92037.
authors.forename: Amy
authors.initials: A
authors.lastname: Frey
authors.affiliation: Marine Mammal & Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration 8901 La Jolla Shores Drive, La Jolla, California, 92037.
authors.forename: Erin
authors.initials: E
authors.lastname: LaCasella
authors.affiliation: Pacific Islands Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration 1845 Wasp Blvd., Honolulu, Hawaii, 96818.
authors.forename: George H
authors.initials: GH
authors.lastname: Balazs
authors.affiliation: Archie Carr Center for Sea Turtle Research and Department of Biology, University of Florida PO Box 118525, Gainesville, Florida, 32611.
authors.forename: Patricia
authors.initials: P
authors.lastname: Zárate
authors.affiliation: Facultad de Biología, Centro Multidisciplinario de Estudios en Biotecnología- UMSNH Morelia, Michoacán, 58030, México.
authors.forename: Omar
authors.initials: O
authors.lastname: Chassin-Noria
authors.affiliation: Dirección de Especies Prioritarias para la Conservación, CONANP Camino al Ajusco 200, 2° piso Ala Sur, Col. Jardines en la Montaña, México, DF, 14210, México.
authors.forename: Adriana Laura
authors.initials: AL
authors.lastname: Sarti-Martinez
authors.affiliation: Kelonian Conservation Society Heredia, Costa Rica.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Velez
keywords: Chelonia mydas; genetic stock structure; marine turtles; mtDNA; phylogeography