Phenotypic variation and sexual dimorphism in anadromous threespine stickleback: Implications for postglacial adaptive radiation

Aguirre, W. E., Ellis, K. E., Kusenda, M., Bell, M. A. (November 2008) Phenotypic variation and sexual dimorphism in anadromous threespine stickleback: Implications for postglacial adaptive radiation. Biological Journal of the Linnean Society, 95 (3). pp. 465-478.

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DOI: 10.1111/j.1095-8312.2008.01075.x


Ancestral properties can influence patterns of evolutionary diversification, but ancestors can rarely be observed directly. We examined variation and sexual dimorphism of morphological traits in an anadromous threespine stickleback population representing the ancestral form for resident postglacial stickleback populations in the area. A combination of traditional and geometric morphometric methods were used to study variation over multiple years in an anadromous population that breeds in Rabbit Slough, Cook Inlet, Alaska. Major armor anomalies were extremely rare but their occurrence at measurable frequencies suggests that significant standing variation for armor phenotypes exists in anadromous populations. Sexual dimorphism was a major source of variation, and most traits differed significantly between sexes, particularly head length, length of the pelvic girdle, and body shape. Consequently, some degree of sexual dimorphism appears to be the ancestral condition for many traits in derived resident freshwater stickleback radiations. Morphological variation among years, especially in body shape, was significant in both sexes, but the magnitude of annual variation was always less than variation due to other factors. Phenotypic means were relatively stable over short time scales. Postglacial stickleback radiations are among the most enlightening cases of adaptive radiation, and our detailed study of variation in an anadromous stickleback population provides crucial insight into a key component of adaptive radiation, the variation on which directional selection acts at the onset of the radiation. © 2008 The Linnean Society of London.

Item Type: Paper
Uncontrolled Keywords: Alaska Ancestral variation Evolutionary diversification Gasterosteus aculeatus Geometric morphometrics adaptive radiation ancestry morphology morphometry natural selection phenotypic plasticity Postglacial sexual dimorphism species occurrence teleost Alaska North America Rabbit Slough United States Gasterosteus Gasterosteus aculeatus Oryctolagus cuniculus
Subjects: Investigative techniques and equipment
CSHL Authors:
Communities: CSHL labs > Sebat lab
Depositing User: CSHL Librarian
Date: November 2008
Date Deposited: 01 Nov 2011 16:51
Last Modified: 28 Feb 2013 17:09

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