Determination of Dispersal Patterns of the Small-mouthed Salamander (Ambystoma texanum) in Eagle Creek Park (Indianapolis, IN)

摘要

Urbanization and the increasing threat of habitat fragmentation are contributing to the significant declines in amphibian populations world-wide. Ambystomatid species are particularly susceptible to habitat fragmentation because they migrate yearly across upland forests to their breeding sites. Habitat changes could be altering the genetic structure in these species; however few studies have focused on this topic and more generally, examined the dispersal patterns of Ambystomatids. In 2003, Clark, Cripe, and Stachniw conducted a study on “Metapopulation Structure of Ambystoma texanum in Eagle Creek Park (Indianapolis, IN) and the Potential for Gene Flow.” They hypothesized that distance limits the dispersal of populations and creates genetically isolated populations. In the present study, I use an integrative approach including landscape ecology and microsatellite analysis in order to test their hypothesis of dispersal patterns and gene flow in small-mouthed salamander populations. I located breeding sites of A. texanum at Eagle Creek Park marked by Van Deman (1998) using GPS, and I described new breeding sites. I located 8 of the 19 sites marked by Van Deman (1998), all of which were still active breeding sites, and I observed evidence of breeding in two sites previously described by Van Deman (1998) as non-breeding. I also located 18 new ephemeral sites, and 15 contained evidence of A. texanum breeding. In addition, I collected larvae from 8 of the breeding sites, with the average sample size being 17 individuals from each pond and used PCR to amplify microsatellite markers for A. texanum for each of these samples. Only one marker, Atex 143, produced successful trials. I determined the allelic composition of 4 ponds and the preliminary results infer that distance limits gene flow in A. texanum. Information from this study provides a valuable starting point for the use of microsatellite markers in determining dispersal patterns of A. texanum. In addition, knowledge of the landscape ecology and hydrology of Eagle Creek Park sets the stage for comparison and long-term monitoring of the A. texanum, demonstrating the impact of urbanization on these wetland populations.