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Spatial patterns of morphological and genetic polymorphisms between the two banded killifish sub‐species (Fundulus diaphanus diaphanus and F. d. menona) provide evidence that these sub‐species represent distinct evolutionary lineages corresponding to glacial races of Atlantic and Mississippian origins. Individuals with intermediate phenotypes in Lake Ontario and the upper St Lawrence River probably result from secondary contacts between these races. The hybrid zone unexpectedly extends to Lake Erie and involves the introgression of the F. d. diaphanus mitochondrial genome into fish with morphology like that of F. d. menona.
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April et al. (2006) studied this question.
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