ABSTRACT Lake charr ( Salvelinus namaycush ) head and body variation were compared among lakes across the species range in North America, to determine if variation was organized more strongly among morphs or lakes. For 3445 lake charr, head‐shape variation was > 17 times greater among morphs than lakes and body‐shape variation was > 16 times greater among morphs than lakes. Body depth, head depth, caudal peduncle length and depth, pectoral and pelvic fins lengths, and preorbital length varied more among morphs than lakes. Four morphs were delineated based on cluster analysis of combined head and body shape. The fat–fat (short head + fat body) morph had a shorter preorbital head length, deeper head and body, shorter and deeper caudal peduncle, and longer paired fins than the lean–lean (long head + slender body) morph, which had a longer preorbital length, shallower head and body, longer and narrower caudal peduncle, and shorter paired fins. The fat–lean (short head + slender body) morph was similar to the fat–fat morph in preorbital length, body depth, caudal peduncle length, and paired fin lengths, but not in head depth or caudal peduncle depth. The lean–fat (long head + fat body) morph was similar to the fat–fat morph in body depth, head depth at the eye, caudal peduncle length, and paired fin lengths, but was similar to the lean–lean morph in maximum head depth and preorbital length. The most extreme fat–fat morphs were from widely separated Great Bear Lake and Lake Superior, whereas the most extreme lean–lean morphs were from Skilak Lake (Alaska), Lake Superior, and Great Bear Lake. The lean–lean morph, present in every lake, was the common morph. A fat–fat morph was present in multiple lakes, but differed greatly in ecological function among lakes, which was more consistent with a hypothesis that multiple lake charr morphs differentiated in multiple lakes across the species' range, rather than were derived from a single already‐specialized morph that colonized multiple lakes from common glacial refugia.
Hansen et al. (Fri,) studied this question.