Dissertations, Theses, and Capstone Projects

Date of Degree

9-2025

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy

Program

Biology

Advisor

Brian T. Smith

Committee Members

Michael J. Hickerson

Ana C. Carnaval

Frank T. Burbrink

Benjamin Winger

Subject Categories

Biodiversity | Evolution | Genomics | Ornithology | Other Ecology and Evolutionary Biology

Keywords

Mountains, Biogeography, Macroecology, Species diversification, Macroevolution

Abstract

The origin and maintenance of the tropical montane diversity have been evaluated over multiple decades using various techniques and perspectives. Despite major progress in understanding phylogenetic relationships, diversification patterns, distributional data, and general ecology in the Andean biota, large gaps in our understanding remain, particularly in the synthesis across scales. To fill these gaps, I aimed to explore patterns and processes that underlie species diversification in birds of the tropical Andes of South America by combining different approaches using phenotypic, phylogenetic, and genomic data in multiple temporal and spatial scales.

In the first chapter, I examined the macroevolutionary patterns of species diversification and ecological factors (morphological disparity and spatial segregation) interact to facilitate species accumulation in Neotropical montane clades. I found that montane clades have evolved under equilibrium and nonequilibrium dynamics. This result suggests that, at macroevolutionary scales, ecological factors interact to generate and maintain the high avian diversity in Neotropical mountains, but that regional diversity may be less constrained by ecological limits.

In the second chapter, I collected birds' phenotypic data (external morphology and color data) to test the hypothesis that competitive interaction mediates the strong elevational replacement patterns in communities occurring in Neotropical mountains. I found that in one clade characterized by vivid colors (oscines), species with similar coloration replace in elevation (competitive exclusion), whereas more dissimilar species can co-occur in their distribution (character displacement). I did not find this same relationship when considering the morphological data, suggesting that competition, in terms of species recognition but not for resource access, may determine the elevational replacements in tropical mountains.

In the third chapter, using a landscape genomic approach, I investigated the role of neutral and adaptive variation in the spatial genetic divergence in the eastern Cordillera of the Colombian Andes. By sampling 175 genomes from ten bird species, I found that the overall genetic variation was mainly associated with precipitation-related variables. However, when using just the putative adaptive variation, genetic differentiation was better linked to temperature-related variables, suggesting that adaptive processes might be important in explaining the population divergence in mountains.

Taken together, I provide evidence of how stochastic and non-stochastic processes may work in concert, driving gradients of population genetic structure to assemblage-level phylogenetic structure across an elevational gradient, which helps explain the origin of species richness patterns from micro- to macro-evolutionary levels. At macroevolutionary scales, these dynamics result in different eco-evolutionary trajectories given the differential contribution of historical and ecological factors among clades. Therefore, my work shows a link between microevolutionary adaptive processes and the mountain’s environmental attributes that contribute to the building of the origin of regional diversity patterns, while competitive interactions, inferred from phenotypic data, facilitate the maintenance of such diversity patterns at the ecological and evolutionary time scales.

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