Research Product

Experimental crosses with four allozymically-defined clones of the Menidia clarkhubbsi complex of unisexual fishes are consistent with expectations for gynogenetic reproduction. Successful reproduction occurred after exposure of eggs to milt from either of the bisexual species, M. beryllina or M. peninsulae, while eggs not exposed to milt failed to initiate embryogenesis. Progeny assayed allozymically were identical to the mother, and all of those assessed for sex were females. Rare occurrences of wild-caught triploids suggest occasional amphimixis between eggs from the M. clarkhubbsi complex and haploid sperm from the bisexual species. The evolutionary origin of the unisexual complex is reviewed against the background of new data on geographic surveys and clonal diversity. The various clones appear to have arisen polyphyletically through multiple hybridizations between M. beryllina and a missing ancestral population similar to M. peninsulae.