Historical relationships among nematodes and their mammalian hosts across the neotropics. In particular, I am interested in having a better understanding of the phenomena of host capture and host switching. By dissecting the intricate evolutionary histories of both mammals and parasites, I plan to obtain a better understanding of the processes that resulted in the diversification of the fauna of the New World. Additionally, the study of nematode parasitoses may provide valuable insights into the dynamics in the transmission of parasites to syntopic hosts. The understanding of the historical associations among parasites and their hosts necessitates the completion of several subsidiary goals. First, the biodiversity of the Neotropics needs to be inventoried by describing the species that occur across the diverse biomes. Second, the distribution of those species needs to be documented in detail, since there are areas of the continent with little or no information about the distribution of parasites. Third, we need to postulate robust phylogenetic hypotheses of those groups of parasites that occur across the Neotropics, analyzing and understanding the available evidence.