Identifier

etd-04152010-114242

Degree

Doctor of Philosophy (PhD)

Department

Biological Sciences

Document Type

Dissertation

Abstract

In this dissertation I explored the processes that generated high species diversity in a continental adaptive radiation of passerine birds: the family Furnariidae. Although there is a vast amount of information on the microevolutionary mechanisms that generate speciation and adaptation, much less is known about the processes underlying large-scale patterns of diversity. I used new techniques that exploit information contained in phylogenetic trees to investigate the diversification process in Furnariidae at a macroevolutionary scale. First, I conducted the first quantitative study that demonstrated that the Furnariidae constitute a case of rapid diversification in both species numbers and morphology as compared to six closely related families. To evaluate phenotypic diversity, I developed a new multivariate extension of the variance, which I called 'proper variance', and a new simulation procedure to test for differences in phenotypic diversity when complete phylogenies are not available. I found that the Furnariidae, although not particularly diverse in body size, is unusually diverse in shape. These results support the idea that the Furnariidae constitute a continental adaptive radiation. To explore processes responsible for high species diversity in the Furnariidae, I first investigated the effect of dispersal ability on species proliferation. Assuming that dispersal in birds is highly influenced by flying ability, I used an index of wing shape as a surrogate for flying ability. Using a nearly complete species-level phylogeny of the Furnariidae and a recently developed method, I found a negative correlation between flying ability and speciation rates, suggesting that low dispersal has stimulated species proliferation in Furnariidae. Finally, I investigated the effect of three key innovations on furnariid diversification: adaptations for trunk climbing, spiny-tail morphologies, and skull kinesis. I found that increases in diversification rates are not associated with major morphological changes. In addition, I found that climbing specialization had a negative effect on speciation rates, but that the spiny-tail morphology was positively correlated with speciation rates. These results provide mixed support for a role of key innovations promoting speciation. My results suggest a stronger role of geographic isolation (low dispersal) than ecological opportunities in species diversification in the continental radiation of the Furnariidae.

Date

2010

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Remsen Jr., James V.

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