Range expansion of an exotic Asian snail (Melanoides tuberculata) into central Texas rivers, and the parasitological consequences thereof
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The invasive gastropod Melanoides tuberculata (Thiaridae) has been established in Texas since the 1960’s (Murray, 1964). For decades, sensitivity of these snails to cold winter temperatures restricted reproducing populations of the snail to thermally stable waters (Fleming 2002, Rader et al., 2003, Mitchell and Brandt, 2005). The mechanisms driving this expansion are not yet understood but parasitic consequences of this phenomenon are such that the invasive Asiatic trematodes Centrocestus formosanus, Haplorchis pumilio, and Philophthalmus gralli are likely to follow their snail hosts into novel habitats from which they were previously excluded. Non-Metric Multidimensional Analysis was used as a distance based comparison of phenotypic characteristics in attempt to qualitatively partition morphometric variation observed within and among several Texas snail populations. Snails exhibiting unique combinations of phenotypic characters were subject to molecular analyses using primers targeting the mitochondrial 16s rRNA gene. Genetic analyses revealed pockets of genetic variation within and among the studied populations. Genetic diversity of local snail populations was placed into a global context using 16s rRNA sequence data available from GenBank. Additionally, geometric estimates of conch morphology were used to further partition subtle variation via multivariate analyses. This dual perspective is a starting point for future studies investigating niche preferenda and genetic diversity of M. tuberculata populations established in the United States.