Hybridization of Two Darter Species Native to Central Virginia

Spawning behavior and hybridization of Etheostoma nigrum and E. olmstedi were studied in the lab using wild individuals collected from populations in central Virginia. Hybridization is common in the genus Etheostoma, but there have been conflicting results in studies involving E. nigrum and E. olmstedi. The question is pertinent to central Virginia because populations with characteristics intermediate of the two species occur there, and it may be that these are hybrids. We collected both darter species in the wild and placed various inter- and intra-specific mating pairs in small aquaria. Males spent more time than females in nuptial behavior (24.1% v. 7.5%), the percentages were not different between species, but E. nigrum males spent more time courting E. olmstedi females than they did their own species (32% v. 12.4%). Viable eggs were produced in 6 of 24 tanks, including two inter-specific crosses. In both inter-specific crosses the female was E. olmstedi and the male was E. nigrum. Fry were produced from all six successful matings, but 100% mortality occurred by week four, probably because we did not provide a suitable diet.

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