Cytonuclear evidence for hybridogenetic reproduction in natural populations of the Australian carp gudgeon (Hypseleotris: Eleotridae).

Although most vertebrates reproduce sexually, a small number of fishes, amphibians, and reptiles are known in which reproduction is asexual i.e. without meiotic recombination. In fishes, these so-called “unisexual” lineages usually comprise only females, and utilize co-occurring males of a related sexual species to reproduce via gynogenesis or hybridogenesis. Here we examine patterns of microsatellite and mitochondrial DNA (mtDNA) variation in a widespread group of freshwater fishes (carp gudgeons; Hypseleotris spp.) to investigate a long-standing proposal that this group includes unisexual forms. We show that the mtDNA genome of most carp gudgeons in tributaries of the Goulburn River belong in one of two deeply divided clades (~10% cyt b divergence) and that nuclear variation divides the same individuals into four distinct groups. Group 1 exhibits the genotypic proportions of a random mating population and has a 1:1 sex ratio. Two other groups are extremely sex-biased (98% male, 96% fe...