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Microgeographical diversification of threespine stickleback: body shapehabitat correlations in a small,

Summary: Microgeographical diversification of threespine
stickleback: body shape­habitat correlations in a small,
ecologically diverse Alaskan drainage
Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY 11794, USA
Received 28 December 2008; accepted 23 March 2009bij_1267 139..151
Adaptive radiations are a major source of evolutionary diversity in nature, and understanding how they originate
and how organisms diversify during the early stages of adaptive radiation is a major problem in evolutionary
biology. The relationship between habitat type and body shape variation was investigated in a postglacial radiation
of threespine stickleback in the upper Fish Creek drainage of Cook Inlet, Alaska. Although small, the upper Fish
Creek drainage includes ecologically diverse lakes and streams in close proximity to one another that harbour
abundant stickleback. Specimens from ancestral anadromous and derived resident freshwater populations differed
substantially and could be distinguished by body shape alone, suggesting that the initial stages of adaptation
contribute disproportionately to evolutionary divergence. Body shape divergence among resident freshwater
populations was also considerable, and phenotypic distances among samples from freshwater populations were
associated with habitat type but not geographical distance. As expected, stream stickleback from slow-moving,
structurally complex environments tended to have the deepest bodies, stickleback from lakes with a mostly benthic
habitat were similar but less extreme, and stickleback from lakes with a mostly limnetic habitat were the most
shallow-bodied, elongate fish. Beyond adapting rapidly to conditions in freshwater environments, stickleback can
diversify rapidly over small geographical scales in freshwater systems despite opportunities for gene flow. This


Source: Aguirre, Windsor E. - Department of Ecology and Evolution, SUNY at Stony Brook


Collections: Biology and Medicine