Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Population genetics of estuary and reservoir populations of Harris mud crabs, Rhithropanopeus harrisii, in Texas and Oklahoma.

Abstract

Rhithropanopeus harrisii are small, estuarine crabs native to the Atlantic and Gulf coasts of North America. They have become an invasive species, establishing populations on the west coast of the United States, Europe, Panama, and Japan. Reproducing populations are also established in freshwater reservoirs in Texas and on the Texas/Oklahoma border. In order to compare levels of genetic diversity within introduced reservoir populations with those of native estuary populations and to determine possible source populations and routes of colonization among Texas reservoir populations, we obtained mitochondrial DNA sequences from reservoirs and several estuaries along the Texas and Louisiana coast. Overall, genetic diversity within reservoirs was lower than within estuaries; however, some reservoirs exhibited relatively high levels of genetic diversity indicating that they were founded by numerous individuals or individuals from divergent source populations. In contrast, two genetically divergent reservoir populations had greatly reduced genetic diversity suggestive of extreme founder effects. All estuary and reservoir haplotypes formed a monophyletic group separate from Atlantic coast haplotypes, thus colonization of Texas reservoirs occurred from the Gulf Coast as expected based on geographic proximity. There was minimal DNA sequence divergence among Gulf Coast and reservoir haplotypes and a lack of phylogeographic structure among estuary populations. However, there was significant population divergence among some estuaries based on haplotype frequencies. Genetic differences among estuaries were subtle in most cases, preventing identification of source populations using mitochondrial DNA sequences.