Polymorphism in lake trout in Great Bear Lake: intra-lake morphological diversification at two spatial scales

Abstract

Great Bear Lake is the most northerly lake of its size and provides unique opportunities for intraspecific diversification. Despite increasing attention to intraspecific polymorphism, several knowledge gaps remain (e.g. determining the extent of intraspecific diversification in large relatively pristine lakes and at which spatial scale it can occur). We focused on geographical patterns of morphological differentiation within lake trout (Salvelinus namaycush) to describe two levels of intralake diversification in Great Bear Lake. We used a combination of geometric and traditional linear measurements to quantify differences in body shape, head shape, and fin and body lengths among 910 adult lake trout from the five distinct arms of Great Bear Lake. Although head and fin linear measurements discriminated the three common morphotypes at the whole‐lake level, inter‐arm variation in body shape was observed within each morphotype. A comparison of genetic and morphological distance matrices revealed the lack of an association between the two sets of data, although both comparisons revealed an association in the inter‐arm variation patterns among morphotypes, suggesting a phenotypically plastic response to distinct environments. The whole‐lake and inter‐arm morphological variation observed within lake trout demonstrates the importance of considering scale, especially across large lakes that exhibit marked complexity and a variety of freshwater habitats. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 114, 109–125.

Multiple generalist morphs of Lake Trout: Avoiding constraints on the evolution of intraspecific divergence?

“…Indeed, considerable intraspecific diversity and plasticity have been documented within the shallow‐water regions of Great Bear Lake (Alfonso ; Blackie et al. ;Chavarie, Howland, Harris, & Tonn, ; Chavarie, Howland, & Tonn, ; Chavarie, Howland, Venturelli et al., ). Such shallow‐water diversity could be an undervalued characteristic of the species across its broader geographic range, for example, historical anecdotes of similar polymorphisms only exist for the Laurentian Great Lakes (Brown, Eck, Foster, Horrall, & Coberly, ; Goodier, ).…”

“…Within the shallow‐water (≤30 m) zones of Great Bear Lake, four morphs differed in head, body, and fin morphology (Figure ) (Chavarie, Howland, Harris et al., ; Chavarie, Howland, Venturelli et al., ; Chavarie et al., ). Morph 1 was characterized by a smaller head and intermediate fins, Morph 2 had the largest head and jaws but smallest fins, Morph 3 had the longest fins and a robust body shape, and Morph 4 had a thick curved lower jaw and the smallest caudal peduncle of the morphs.…”

“…(a) Map of Great Bear Lake, Northwest Territories, Canada, adapted from Johnson () and Chavarie, Howland, Harris et al. (), indicating general bathymetry and its major rivers. Insert: location of study area within Canada.…”

Inter and intra‐population phenotypic and genotypic structuring in the European whitefish Coregonus lavaretus, a rare freshwater fish in Scotland

“…alpinus (Danzmann et al , ; Adams et al , ; Fraser et al , ; Knudsen et al , ). At least for some species, the geographic scale of the habitat appears to be an important factor influencing phenotypic and genetic structuring (Chavarie et al , ).…”

Life history differences between fat and lean morphs of lake charr (Salvelinus namaycush) in Great Slave Lake, Northwest Territories, Canada

“…In Great Bear Lake, several morphologically distinct morphs of shallow-water lean lake charr have been described (Blackie et al, 2003;Alfonso, 2004;Chavarie et al, 2013Chavarie et al, , 2014Chavarie et al, , 2015a. In Great Slave Lake, a fat morph occupied mostly deep waters, ate mostly invertebrates, especially opossum shrimp, had a narrow caudal peduncle, light body color, greater buoyancy, and deep anterior body, whereas a sympatric lean morph occupied mostly shallow waters, ate mostly fish, were streamlined in shape, darker in color, and less buoyant (Zimmerman et al, 2006(Zimmerman et al, , 2009.…”