A dynamic geological history, complex topography, and high species richness characterize the tropical Andes. Endemic radiations comprise a major component of this high diversity and evaluating the spatial and temporal context in which these radiations diversified provides an informative framework to understand the processes facilitating speciation in the Andes. Metallura hummingbirds are a diverse genus endemic to the Andes that are widely distributed geographically and ecologically making them well suited to investigating Andean speciation. In the first chapter I apply phylogenetic methods to address the relative roles of geological history, physical barriers, and environmental heterogeneity in the Metallura radiation. I found Metallura diversification to be primarily associated with Pleistocene glacial cycles. The two main clades recovered in all phylogenetic analyses exhibited contrasting histories of spread through the Andes. One clade, the M. aeneocauda superspecies, diverged from south-to-north through the Andes, whereas a second clade, the widespread M. tyrianthina, shows a northern origin followed by spread southward. Finally, river valleys played a prominent role in structuring genetic diversity in both clades. Environment played little role with genetic structure only existing in conjunction with physical barriers. Secondly, I compare patterns of genetic and morphological variation within Peruvian populations of Metallura tyrianthina to evaluate how geographic isolation and environmental heterogeneity interact to drive divergence. Longer bills were found in populations occurring in more seasonal environments regardless of taxonomy or geographic proximity. Conversely, physical barriers structured genetic variation. A more detailed investigation of four populations in southern Peru also revealed that bill length increased in more seasonal environments. However, both morphological and genetic differences were greater in the presence of a physical barrier. These results indicate that the physical barriers and environmental heterogeneity created by a complex Andean topography operate in concert to drive speciation.
Andean birds, speciation, glaciation, uplift, environmental heterogeneity, Metallura
Level of Degree
UNM Biology Department
First Committee Member (Chair)
Second Committee Member
Benham, Phred. "The role of geological history, topography, and environmental heterogeneity in the diversification of an endemic Andean radiation : the Metallura hummingbirds." (2012). https://digitalrepository.unm.edu/biol_etds/6