title: Importance of dispersal routes that minimize open-ocean movement to the genetic structure of island populations.
abstract: Islands present a unique scenario in conservation biology, offering refuge yet imposing limitations on insular populations. The Kimberley region of northwestern Australia has more than 2500 islands that have recently come into focus as substantial conservation resources. It is therefore of great interest for managers to understand the driving forces of genetic structure of species within these island archipelagos. We used the ubiquitous bar-shouldered skink (Ctenotus inornatus) as a model species to represent the influence of landscape factors on genetic structure across the Kimberley islands. On 41 islands and 4 mainland locations in a remote area of Australia, we genotyped individuals across 18 nuclear (microsatellite) markers. Measures of genetic differentiation and diversity were used in two complementary analyses. We used circuit theory and Mantel tests to examine the influence of the landscape matrix on population connectivity and linear regression and model selection based on Akaike's information criterion to investigate landscape controls on genetic diversity. Genetic differentiation between islands was best predicted with circuit-theory models that accounted for the large difference in resistance to dispersal between land and ocean. In contrast, straight-line distances were unrelated to either resistance distances or genetic differentiation. Instead, connectivity was determined by island-hopping routes that allow organisms to minimize the distance of difficult ocean passages. Island populations of C. inornatus retained varying degrees of genetic diversity (NA = 1.83 - 7.39), but it was greatest on islands closer to the mainland, in terms of resistance-distance units. In contrast, genetic diversity was unrelated to island size. Our results highlight the potential for islands to contribute to both theoretical and applied conservation, provide strong evidence of the driving forces of population structure within undisturbed landscapes, and identify the islands most valuable for conservation based on their contributions to gene flow and genetic diversity.
authors.affiliation: School of Veterinary and Life Sciences, Murdoch University, 90 South Street, Western Australia, 6150, Australia.
authors.forename: E L
authors.initials: EL
authors.lastname: Harradine
authors.affiliation: School of Veterinary and Life Sciences, Murdoch University, 90 South Street, Western Australia, 6150, Australia.
authors.forename: M E
authors.initials: ME
authors.lastname: Andrew
authors.affiliation: School of Veterinary and Life Sciences, Murdoch University, 90 South Street, Western Australia, 6150, Australia.
authors.forename: J W
authors.initials: JW
authors.lastname: Thomas
authors.affiliation: School of Anatomy, Physiology & Human Biology, The University of Western Australia, Crawley, WA, 6009, Australia.
authors.forename: R A
authors.initials: RA
authors.lastname: How
authors.affiliation: School of Anatomy, Physiology & Human Biology, The University of Western Australia, Crawley, WA, 6009, Australia.
authors.forename: L H
authors.initials: LH
authors.lastname: Schmitt
authors.affiliation: School of Veterinary and Life Sciences, Murdoch University, 90 South Street, Western Australia, 6150, Australia.
authors.forename: P B S
authors.initials: PB
authors.lastname: Spencer
mesh_terms: D063147:Animal Distribution; D000818:Animals; D003247:Conservation of Natural Resources; D051456:Gene Flow; D014644:Genetic Variation; D062312:Islands; D008116:Lizards / Q000235:genetics / Q000502:physiology*; D018895:Microsatellite Repeats; D014904:Western Australia
keywords: CIRCUITSCAPE program; Ctenotus inornatus; aislamiento por resistencia; bar-shouldered skink (Ctenotus inornatus); biogeografía de islas; conectividad; connectivity; deriva génica; genetic drift; genética de paisajes; island biogeography; isolation by resistance; landscape genetics; programa CIRCUITSCAPE