Evaluation of molecular approaches used to estimate population size and of factors influencing population size and success of introduced or reintroduced wildlife

Knowledge of the factors influencing the demography of small and introduced populations is critical to understanding their productivity and viability. Molecular markers are providing new means to obtain estimates of population abundance of invasive species. I evaluated several sources of error associated with molecular identification techniques that could bias population estimates. Population estimates were biased downward as the likelihood of individuals sharing the same genotype increased. Errors in genotype assignment resulted in over estimates of population size. When possible, only highly polymorphic loci critical to the identification of the individual should be used in molecular tagging, and considerable efforts should be made to minimize errors in genotype determination.; Release programs are often a major conservation strategy used to protect endangered species. In order to examine the effects of inbreeding and captive breeding on introduced populations, I identified experimental release sites where Mus musculus did not occur previously. In preparation for M. musculus experimental introductions, I surveyed twelve islands in the Atchafalaya Delta for small mammals; mammalian faunas of deltaic islands are often poorly documented because these islands are remote and may exist for a limited period of time. Densities of Oryzomys palustris and Sigmodon hispidus were 3–4 times higher than previously reported estimates for these species, but M. musculus was not found on the islands. Success of experimental releases was poor over the 8-month study, however survival of wild-caught individuals was greater than captive-bred individuals. I analyzed past accounts on mammal and bird releases to determine factors affecting success of the release events. I found release success or growth of the released population was influenced by release location, source origin (captive or wild), number of individuals released, the effective size of the founder population, size of release site, and presence or absence of predators and competitors. Of these factors, releases inside a species' historic range, release of a large number of individuals, and release of wild-caught individuals had the largest positive effects on release outcome.