Diaz-Nieto, Juan2016-08-192016-08-192016-04https://hdl.handle.net/11299/181716University of Minnesota Ph.D. dissertation. April 2016. Major: Ecology, Evolution and Behavior. Advisor: Sharon Jansa. 1 computer file (PDF); xii, 210 pages.This research presents the results of collaborative work with Sharon A. Jansa and Robert S. Voss on the systematics of the American marsupials of the genus Marmosops. Chapter 1 evaluates the species-level diversity of this genus using mitochondrial sequences from >200 specimens, including exemplars of every currently recognized species together with a dense intraspecific sampling. These data are analyzed using the General Mixed Yule Coalescent (GMYC) model and the results suggest that the genus could be twice as speciose as currently recognized. Additionally, the phylogenetic relationships within Marmosops are evaluated using sequences of the Breast Cancer Type 1 susceptibility gene (BRCA1). These analyses reveal a basal dichotomy between two ancient, morphologically diagnosable clades. Based on the latter results, a taxonomic proposal is made with the description of a new subgenus, Sciophanes. Chapter 2 includes a revision of the species of subgenus Sciophanes in the context of the molecular analyses of Chapter 1. This revision recognizes 12 valid species in three monophyletic species groups: the Parvidens Group (including M. pakaraimae, M. parvidens, and M. pinheiroi), the Fuscatus Group (M. carri, M. fuscatus, M. handleyi, and M. invictus), and the Bishopi Group (M. bishopi, M. juninensis, M. ojastii, and two new species). For each species, information about type material, ecogeographic distribution, and diagnostic morphological characters is presented. Chapter 3 evaluates the phylogenetic relationships of the tribe Thylamyini by using a multi-locus dataset. In particular, this chapter aims to resolve evolutionary relationships of the thylamyine genus Chacodelphys. A previous understanding of the species-level diversity within Marmosops is crucial for constructing a phylogeny of Thyamyini because this genus accounts for almost 45% of the diversity within the tribe. Phylogenetic analyses of these data convincingly resolves Chacodelphys as the sister taxon of Cryptonanus and supports most of the previous phylogenetic arrangements obtained within Marmosops.enAmerican marsupialsDidelphidaeMolecular systematicsNew speciesNew subgenusTaxonomyThesis or Dissertation