A systematic study of two species complexes of the genus Fundulus (Pisces: Cyprinodontidae)

Abstract

Two Fundulus species complexes, the Fundulus heteroctitus-F. grandis and F. maialis species complexes, have nearly identical Overall geographic ranges (Canada to northeastern Mexico and New England to northeastern Mexico, respectively; both disjunctly in Yucatan). Fundulus heteroclitus (Canada to northeastern Florida) and F. grandis (northeastern Florida to Mexico) are valid species distinguished most readily from one another by the total number of mandibular pores (8 and 10, respectively) and the long anal sheath of female F. heteroclitus. Fundulus majalis and F. similis are conspecific (F. majalis has nomenclatural priority) and intergrade in northeastern Florida in the same region in which F. heteroctitus and F. grandis are sympatric. Overlapping populations in other species groups of fishes, notably Sphoeroides, Chasmodes, and Menidia, occur in the same northeastern Florida area. Both Fundulus population complexes have disjunct Gulf and Atlantic populations, differentiated allopatric populations in the Florida Keys (and Cuba for F. grandis), and allopatric related species in Yucatan (F. grandissimus and F. persimilis). Presumably F. grandis and southerly F. majalis ("similis-type") evolved in the Gulf of Mexico in isolation from Atlantic coast ancestors during some Pleistocene interglacial period, and have recontacted Atlantic populations in northeastern Florida since the Wisconsin glaciation. Yucatan populations of Fundulus, Floridichthys, Menidia, and Cyprinodon and Florida Keys populations of Fundulus, Menidia, Syngnathus, and possibly Lucania and Cyprinodon are considered to be glacial relicts.