| Two subspecies of banded killifish (F. diaphanus diaphanus and F. d. menona) are respectively found in the eastern and western parts of the species range. Although these subspecies are defined on the basis of morphological traits, individuals with intermediate phenotypes are reported in Lake Ontario and the upper Saint Lawrence River. In this study, we describe spatial patterns of morphological and genetic (mitochondrial: D-loop; nuclear: intron of the X-src gene) polymorphisms supporting two principal hypotheses: (1) populations recognized as subspecies represent distinct evolutionary lineages corresponding to Atlantic and Mississippian glacial races and (2) Lake Ontario and the upper Saint Lawrence River, where individuals with intermediate morphological features are indeed present, correspond to a zone of secondary contact with hybridization. This hybrid zone, extending to Lake Erie, is wider than previously described and appears to involve the introgression of F. d. diaphanus mitochondrial genome into that of F. d. menona. |
