Phylogeographic analysis of the threatened and endangered superconglutinate-producing mussels of the genus Lampsilis (Bivalvia : Unionidae)

Several species of freshwater unionid mussels in the genus Lampsilis exhibi t a remarkable reproductive strategy. Female mussels of these species enclo se their larvae in a minnow-like lure, called a 'superconglutinate', to att ract piscivorous fishes. When a fish attempts to ingest the superconglutina te the lure ruptures and the larvae are released to parasitize the fish. Of the four species of mussel which exhibit this strategy and are endemic to the Gulf Coast drainages of the southeastern United States, three are prote cted under the Endangered Species Act, and one is recognized as imperilled. Phylogenetic analysis of nucleotide sequences of the mitochondrial 16S rib osomal RNA and the first subunit of the cytochrome oxidase c genes was cond ucted on IS individual specimens representing these four species and six ou tgroup taxa. Phylogenetic analyses of these data support the monophyly of t he superconglutinate-producing mussels, and indicates a strong geographical component to the data. The zoogeographic patterns of the four taxa include d in the study are congruent with those seen in freshwater vertebrates, and are consistent with a vicariant pattern resulting from fluctuations in sea level during the Pleistocene. Despite the strong geographical structuring of the data, only one species, Lampsilis subangulata, was recovered as mono phyletic. The authors attribute the lack of support for the monophyly of th e remaining species to insufficient sequence variation and the recent origi n of the ancestor of these taxa. Based on these data, any future captive br eeding projects aimed at augmenting or re-establishing populations should d o so only from the appropriate source populations so as to maintain the gen etic integrity of these nascent species.