Biochemical genetics of Fundulus heterolitus (L.). I. Temporal and spatial variation in gene frequencies of Ldh-B, Mdh-A, Gpi-B, and Pgm-A.

Natural populations of Fundulus heteroclitus show extensive spatial variation in gene frequencies at four unlinked polymorphic loci. Large clinal changes in gene frequencies were found for Ldh-B, Mdh-A, and Gpi-B, whereas the spatial variation for the Pgm-B locus was small. Since the geographical area over which these clines are found is characterized by a steep thermal gradient, the clines in gene frequency are correlated with a directional change in mean water temperature. Maximum gene diversity of these four loci was correlated with annual fluctuations in water temperature. Temporal stability of the allelic frequencies was established for a 2--4 year period.