Date of Award

1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Robert M. Zink

Abstract

This dissertation presents data on the biogeography and molecular systematics of seven independent lineages of birds; both allozyme and mitochondrial DNA (mtDNA) characters were used. The purpose of this study was to discover biogeographic patterns among endemic taxa distributed in the highlands and lowlands of southern Central America and sister taxa in either North or South America. Analyses of the genera Diglossa, Buarremon, Pselliophorus, and Pezopetes suggested a complex biogeographic pattern in the highlands of southern Central America; divergence of some highland lineages occurred relatively recently (during the Pleistocene), after the landbridge connection between Central and South America was completed, whereas divergence of other birds occurred more anciently (8-10 million years ago) before the landbridge was completed. In addition, both northern (North America, northern Middle America) and southern (South America) sources of taxa contributed to the endemicity in the highlands of southern Central America. Analyses of lowland lineages (Gymnopithys, Pteroglossus, and Ramphocelus) suggested a single area cladogram for lowland areas of endemism: Pacific and Caribbean Central American areas of endemism as sister areas, Choco (western South America) as the sister area to the Central American areas of endemism, and Amazonia as the sister to the Central American/Choco areas. Analysis of Pipra suggested a different area cladogram relative to the other three lineages; however, a cladogram of one step longer supported the general area cladogram suggested by the other three lowland lineages. Examination of rates of molecular divergence suggested that Pteroglossus taxa are much less differentiated across similar geographic areas than are the other lowland lineages, possibly the result of Pteroglossus possessing increased dispersal abilities relative to the other lowland lineages. There was a high degree of evolutionary concordance of both mtDNA and allozyme characters. However, mtDNA sequence data (from the cytochrome b gene) reached the multiple hit zone after approximately 10% sequence divergence, a result consistent with other studies of the cytochrome b gene.

Pages

191

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