Research Document - 2013/107
Patterns of morphological diversity in ciscoes distributed within three of Manitoba’s glacial relict lakes, with reference to Shortjaw Cisco (Coregonus zenithicus)
By Boguski, D.A., Murray, L., Pratt, T.C., Johnson, J.D., and Reist, J.D.
Abstract
Shortjaw Cisco, Coregonus zenithicus, show exceptional levels of phenotypic diversity occurring in numerous postglacial lakes in North America. Here, we contrast the morphological diversity of the species from its type locality in Lake Superior to three continental lakes (Reindeer, Athapapuskow, and George lakes) in Manitoba using traditional morphological methods. In particular, we investigate if morphological variation exists among and within lakes given the potential for distinct morphologically adapted groups. Discriminant function analyses based on 26 morphological variables revealed that C. zenithicus from Lake Superior represents a distinct morph relative to putative conspecifics in Manitoba, and that morphological structure is strongly mediated by geography (i.e., location) and morphometry of the lake. Gill-raker counts, a highly heritable trait, showed nearly discrete distributions for up to three sympatric general cisco morphs within a lake; only a single morph from Reindeer Lake had similar gill-raker counts to C. zenithicus in Lake Superior despite obvious morphological differences (e.g., a smaller standard length). Consequently, morphotypes may be highly divergent in ecological habits, and thus have important management and conservation implications, but more broad-scale research is required. This study provides corroborating evidence to support the variability of C. zenithicus across its range, and highlights the necessity for re-evaluating the alpha taxonomy of C. zenithicus and closely-related Cisco (C. artedi) species.
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