Genetic and environmental components of phenotypic variation in body shape among populations of Atlantic cod (Gadus morhua L.)

Abstract

A common-garden experiment was conducted on larvae to test for genetic differences in body shape among populations of Atlantic cod (Gadus morhua). Offspring from four north-west Atlantic regions were reared from hatching to postmetamorphosis at two temperatures (7 ± 1 °C and 11 ± 1 °C) and two food levels (1500 and 4500 prey L−1). Body shape differed between populations and treatments. Population differences were greatest between south-west Scotian Shelf cod and those further north; the former were characterized by a deeper body, larger head, and longer caudal peduncle than cod from the other populations. Significant differences were also observed between two putative populations on the south-west Scotian Shelf, suggesting genetic divergence between spawning aggregations at small spatial scales ( 1000 km) and small (< 100 km) spatial scales. The genetic differences at large spatial scales counteracted the expected effects of temperature differences in the wild, suggesting countergradient variation in morphology among these populations. © 2006 Her Majesty the Queen in Right of Canada. Journal compilation © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88, 351–365.