Breeding system and population genetic structure in philomycid slugs (Mollusca: Pulmonata)

Four species of philomycid slugs were collected at 13 sites in Tennessee and one site in Virginia. A total of 361 individuals were examined electrophoretically at 11 allozyme loci. Outcrossing was the primary breeding in all populations of all four species. Genetic similarities among demes, among species and among genera are similar to values obtained in studies of other animals with similar vagility and demography and are in good agreement with systematics based on morphological characters. In the species examined in greatest detail, Philomycus carolinianus , there was substantial genetic differentiation among demes. This differentiation appears to result from genetic drift and restricted gene flow. Genetic similarity between P. carolinianus demes did not correlate with the geographic distance between demes and hierarchical F-statistic analysis showed more than half of the differentiation among demes to result from differentiation at the smallest geographic scale. The Tennessee River system also appears to be a major barrier to gene flow among the P. carolinianus demes sampled.