Research Document - 2013/046
Genetic differentiation and origin of the Shortjaw Cisco (Coregonus zenithicus) in the Great Lakes and other inland Canadian lakes
By J. Turgeon and A. Bourret
Abstract
Ciscoes display a phenomenal level of ecophenotypic diversity throughout their North American range, leading to taxonomic uncertainty and complicating conservation efforts. Predictions associated with three hypotheses on the origin of this diversity, and in particular of the Shortjaw distinct phenotype, are evaluated. These hypotheses are the ‘Plasticity Hypothesis’, the ‘Good Species Hypothesis’, and the ‘Parallel Origin Hypothesis’. Patterns of genetic variation at 290 AFLP loci among 1371 individuals from twenty lakes are analysed, including 387 individual fish identified as (or likely representing) Shortjaw Cisco (Coregonus zenithicus) from 10 lakes. Genetic cluster analyses, association between individual genetic characteristics and phenotypic attributes, genetic re-allocation and analyses of molecular variance were performed. Evidence for the genetic distinctiveness of the Shortjaw Cisco was strong in Lake Nipigon, Trout Lake, Athapapuskow Lake and Great Bear Lake, weak in White Partridge Lake and Lake Superior, and absent in Brule Lake, Lake of the Woods, and Great Slave Lake. It could not be tested in Lake Huron. The Plasticity Hypothesis is dismissed given genetic distinctiveness of morphotypes within many lakes. There is no evidence that Shortjaw Cisco form a distinct lineage, contrary to the predictions of the Good Species Hypothesis. Shortjaw Cisco were always more closely related to sympatric forms than to Shortjaw Cisco from allopatric locations, in accordance with the Parallel Origin Hypothesis. From a genetic and evolutionary standpoint, the Shortjaw Cisco has multiple origins and is diagnosable only at the local scale.
- Date modified: