Testing predictions of adaptive radiation in the passerine avifauna of the Americas
2020-07
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Testing predictions of adaptive radiation in the passerine avifauna of the Americas
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2020-07
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One of the major ideas in macroevolution is adaptive radiation, which predicts that diversification within a clade is coupled with functional trait evolution. This phenomenon occurs in the presence of ecological opportunity and begins with initially high rates of evolution that decelerate through time. While broadly studied and oft-invoked, these predictions have only rarely been tested with multiple clades across a range of phylogenetic and spatial scales. This dissertation uses a phylogenetic comparative framework to test two core prediction of adaptive radiation in independent, biogeographically-delimited clades of oscine songbirds in the Americas by integrating existing and newly-generated phylogenies with a morphometric dataset. In Chapter 1, I inferred the first complete, time-scaled phylogeny for the long-neglected Euphonia and Chlorophonia finches using a phylogenomic approach. This work established the subfamily Euphoniinae as a sound taxon with a young South American origin and several northward dispersal events into the Caribbean and North America. With this clade and 45 additional clades delimited from the existing phylogenetics literature, I then tested two major predictions of adaptive radiation in Chapters 2 and 3. In Chapter 2, I measured functional morphological traits from thousands of museum study skins to quantify each clade’s functional trait disparity and to assess whether variation in this disparity is uniform across these clades. In Chapter 3, I compared a subset of these oscine clades to their sister clades in the Eastern Hemisphere, in addition to comparing the entire oscine assemblage in the Americas to the older, incumbent suboscine clade, to test for signatures of ecological opportunity, constraints, or neutrality. Concordant with the adaptive radiation model, I found that diversification and functional trait evolution appear correlated and surprisingly uniform among the ecologically-disparate clades of oscines in the Western Hemisphere. My Western-Eastern Hemisphere sister clade analyses found support for all three scenarios of opportunity, constraint, and apparent neutrality within the oscine assemblage, but surprising neutrality when comparing the American oscines and suboscines. I ultimately conclude that, to a great extent, the macroevolution of the American oscine avifauna has followed predictions of the adaptive radiation conceptual model.
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University of Minnesota Ph.D. dissertation. 2020. Major: Ecology, Evolution and Behavior. Advisor: Keith Barker. 1 computer file (PDF); 167 pages + 3 supplemental files.
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Imfeld, Tyler. (2020). Testing predictions of adaptive radiation in the passerine avifauna of the Americas. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/241740.
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