Doctor of Philosophy (PhD)
A pervasive goal in evolutionary biology has been to address why some clades are richer in species or phenotypic diversity than others. The Thamnophilidae is a large family of insectivorous passerine birds that provides great opportunities to study variation in species and phenotypic diversity. It comprises ca. 220 species that are mostly restricted to the lowlands and lower montane forests of the Neotropics. Its species are diverse in body size and shape, and the family exhibits high species richness, especially in Amazonian forests, where as many as 40 species may co-occur. Therefore, the fundamental research goal of my dissertation is to understand the relative roles of phylogeny, geography, and ecology in the taxonomic and phenotypic diversification of the antbirds (Thamnophilidae) by integrating the first well-resolved species-level gene-based phylogeny of the family with morphometric, vocal, ecological, and environmental data. A single process neither explains phenotypic diversity nor species diversity in the family, and observed patterns are likely the result of various evolutionary mechanisms acting over time. Temporal patterns of phenotypic diversification in the family are consistent with an important role of adaptive evolution in the Thamnophilidae. Optimal body size values for inhabiting specific habitats and foraging in specific forest strata have accounted for convergent evolution distantly related clades clades. For some specific traits, such as tail, tarsus, and hallux selective pressures have giving rise to distinct morphologies suitable for different environmental conditions that have enabled co-existence and high levels of syntopy at local spatial scales. Species diversity patterns can be explained by the interaction of the effects of time with evolutionary processes that have affected net diversification rates over time. Older lineages tend to exhibit higher species richness and that regions colonized earlier tend to have higher species richness. Furthermore, niche breadth and climatic heterogeneity account for some of the variation that is observed in net diversification rates. Thus, lineages with broader niches tend to speciate less and lineages inhabiting more seasonal and drier environments tend to speciate more.
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Bravo, Gustavo Adolfo, "Phenotypic and Niche Evolution in the Antbirds (Aves: Thamnophilidae)" (2012). LSU Doctoral Dissertations. 4010.
Remsen, Jr., J. V.