Genetic Variation among Ambystoma Breeding Populations on the Savannah River Site

Abstract

We surveyed 16 Carolina bay breeding ponds for Ambystoma salamanders. Tail tissue samples were collected from adult and juvenile mole salamanders (A. talpoideum), marbled salamanders (A. opacum), and spotted salamanders (A. maculatum) captured leaving the Carolina bays. We used amplified fragment length polymorphisms (AFLP) to determine the genetic variation associated with the breeding populations. The Carolina bays could be considered as individual populations, metapopulation groups, or as one big metapopulation depending on gene flow between these bays. Bays range from less than 100 m apart to more than 24 km apart, much further than any reported movement for these species. Animals were marked in the field. We documented little movement of salamanders between breeding locations. Using 392 polymorphic bands produced with the AFLP technique, we were able to separate the samples into the correct species from which the tissues were collected. However, within species analyses failed to find structure associated with populations of salamanders. We failed to document a correlation between geographic and genetic distance (Mantel r = 0.05235, P=0.6800 for mole salamanders; r = 0.46077, P=0.9547 for marbled salamanders). Only 27.8% of mole salamanders and 60.9% of marbled salamanders were assigned back to the population of capture. The majority of the genetic variation was attributable to the individual as opposed to the population. The results of this study suggest that while the majority of these salamanders may be philopatric, some mixing maybe occurring or alternatively, that these populations have not been genetically isolated for sufficient time to develop unique genotypes through drift.