In the 1960s, the gynogenetic fish Poecilia formosa was at least 4.2 times as abundant as its sexual host P. latipinna in habitats in and near Brownsville, Texas. That is consistent with theoretical expectations. In winter 1998–1999, both species were found at 10 sampled ponds and ditches in Brownsville. At 7 of the sites, P. latipinna was more abundant in samples than was P. formosa, while the reverse was true at 3 sites. At all but 1 of the locations, the hypothesis that the gynogen was 4.2 times as abundant as its host was rejected on Chi-square criteria. Whether environmental changes since the historical data were collected in the 1960s have been sufficient to change the relationship between the 2 species, or whether the 2 species vary in relative numbers due to their ongoing population interaction, as suggested by recent experimental evidence, is not yet known.