Hybridization, molecular phylogeography, and population structure: Case studies of clawed frogs and macaque monkeys

Hybrid zones are places where individuals from different populations which are distinguishable by heritable characteristics come into contact and produce hybrid progeny. Hybridization offers a natural experiment with which to study the genetic interface between species which have different behavior, morphology, and biogeography. This thesis examines hybridization of two case studies: clawed frogs (Xenopus gilli and X. laevis laevis) in Cape Province, South Africa, and macaque monkeys (Macaca maura and M. tonkeana) in Sulawesi, Indonesia. The goal is to examine introgression, phylogeny, and population structure of the hybridizing taxa in the context of species-specific behavior, morphology, and biogeography.; In the frog hybrid zone, analysis of mapped restriction sites in the mitochondrial genome (mtDNA) suggests parental taxa are reciprocally monophyletic and that each species has a separate biogeographical history. Populations of X. gilli are disjunct and isolated on either side of its range; sympatric populations of X laevis are continuously distributed with less evidence of vicariance. Morphology, mtDNA, and nuclear DNA (nDNA) suggest that extensive genetic introgression has not occurred between these species.; In the macaque hybrid zone, phylogenetic analysis of mtDNA sequence suggests that Sulawesi was invaded at least twice by Bornean ancestors of M. nemestrina and not by ancestors of another parapatric macaque species, M. fascicularis. One invasion founded macaques in northern and central Sulawesi which is now occupied by M. tonkeana and three other macaque species. A second invasion founded southern Sulawesi, now occupied by M. maura and two other macaque species. Microsatellite analysis suggests population structure exists in both M. tonkeana and M. maura that reflects patterns of dispersal as discerned by mtDNA phylogeny, vicariance, and habitat fragmentation. MtDNA of M. maura and M. tonkeana has a sharp border at their hybrid zone but admixture of nDNA has occurred with a greater genetic contribution from M. tonkeana. Additionally, a portion of M. tonkeana in northwestern central Sulawesi has monophyletic mtDNA; nDNA of this population is highly differentiated from other parapatric populations of M. tonkeana and from M. maura.