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Abstract

Understanding the processes that shape species distributions and how they assemble into communities is central to ecology, yet many mechanisms remain poorly understood. Community phylogenetics adds an evolutionary dimension to ecological analyses, enabling inference of the processes structuring species relationships within and among communities. Although there are a growing number of empirical applications of this framework, further work is needed, particularly through experimental tests of ecological drivers, analyzing patterns across scales, and extending the approach to understudied systems lacking resolved phylogenies. In this thesis, I use community phylogenetics to study invertebrate communities inhabiting Neotropical bromeliads—a model system not previously characterized using molecular or phylogenetic data. Through field experiments and surveys across environmental gradients, I examine phylogenetic structure across spatial and phylogenetic scales, complementing taxonomic patterns to better understand community assembly processes. In Chapter 2, I conducted field experiments in Costa Rica to test how habitat size and predator presence influence taxonomic and phylogenetic diversity. Habitat size had stronger effects during colonization, increasing richness and altering relatedness depending on phylogenetic scale. Predator presence reduced richness during extinction, with more variable effects on phylogenetic structure. In Chapter 3, I examined alpha diversity along an elevational gradient in the Ecuadorian Andes and evaluated environmental drivers. Species richness and phylogenetic dispersion declined as elevation increased, largely due to climate. However, among close relatives, phylogenetic distances increased, suggesting distinct assembly processes at different evolutionary scales. Local conditions also influenced diversity, largely independently from elevation. In Chapter 4, using the same dataset, I examine how the phylogenetic grain of analysis—analogous to taxonomic resolution—alters beta diversity patterns. At the species level, community composition changes markedly with elevation, but these dissimilarities become less pronounced at greater phylogenetic depths. Similarly, site-level contributions to beta diversity vary with phylogenetic depth, reflecting distinct assembly processes across elevations and evolutionary scales. Together, these findings underscore the importance of integrating phylogenetic information into community ecology in order to understand diversity patterns and ecological processes. This work also contributes novel molecular and phylogenetic data for these invertebrate communities, supporting broader efforts to characterize understudied tropical diversity.