Population Differentiation of an Invasive Crayfish Cherax Quadricarinatus on the Island of Puerto Rico

Cherax quadricarinatus is a tropical freshwater crayfish endemic to Northern Australia and Southern Papau New Guinea and was introduced to the island of Puerto Rico for experimental purposes in aquaculture. Species introductions can have multiple effects on the population genetic structure of cultured populations. Population variation may decrease due to bottlenecks and strong selection; or diversity may increase as a result of multiple introductions from diverse native populations. Cultured taxa show high adaptability for available niche space due to breeding for traits such as rapid growth, large size potential, disease resistance and tolerance of stressful environmental conditions. During June-August 2012, populations of C. quadricarinatus were sampled from Puerto Rican reservoirs (e.g. Carraizo, Carite, Cidra, Guajataca, Dos Bocas, Guineo) as well as an aquaculture farm located in the Southwestern town of Lajas. A total of 158 crayfish were caught with a 75:69 reproductive female to reproductive male sex ratio. Catch-Per-Unit-Effort (CPUE= the number of individuals per trapnight) was calculated as an estimate of relative abundance for Cidra, Carite, and Guajataca reservoirs with a CPUE of 2.20, 0.361, 1.033, respectively. Sample sites represent the three main physiographic regions of Puerto Rico (mountainous interior, coastal lowlands, and karst area) from five major watersheds (Eastern, Southern, Interior, Cibuco-Guajataca, and Culebrinas-Guanajibo). Tissue samples were taken from all individuals and brought back to Georgia Southern University to estimate population differentiation. We predict that populations come from the same broad stock and any differentiation of these populations would be a result of genetic drift due to little interaction amongst populations