BIOTIC AND ABIOTIC DRIVERS OF DIVERSIFICATION IN THE OIL-COLLECTING BEE GENUS <i>CHALEPOGENUS</i> (APIDAE: TAPINOTASPIDINI)

Abstract

The oil-bee genus <i>Chalepogenus</i> Holmberg (Apidae: Tapinotaspidini) has unresolved systematics, and can serve as a model to study various ecological traits in driving evolution. The genus is restricted to South America and presents specialized interactions with oil-host plants. However, the ecological preferences in the group were never summarized. In this work I aimed to resolve the evolutionary relationships in the genus and to investigate the traits driving its evolution.To accomplish this, in the first chapter I gathered natural history data (i.e., climate, range/biogeographic, floral-oil preferences, morphology) to evaluate differences and similarities within the morphogroups in the genus. Results show that morphogroups in the genus display clear range differences, floral choices and climatic preferences, which in some cases relate to different morphological traits. These differences and their structure suggest that the spatial and evolutionary history of the genus may have driven changes in the climatic and floral preferences of the ancestors of the taxon. Based on these results, I proposed eco-evolutionary hypotheses, to be tested in a phylogenetic tree. In the second chapter, I used genomic markers and several phylogenetic approaches to build phylogenetic trees and analyze the evolutionary relationships in the group. My results indicate that the genus is not monophyletic, reinforcing the need for a higher-level taxonomic review of the group. Despite this need, our well-supported topologies show that morphogroups and most known species are monophyletic. After summarizing the natural history data and reconstructing phylogenetic relationships, in the third chapter I test eco-evolutionary hypotheses. With this goal, I first estimated the ages of the group and then performed several diversification and ancestral state reconstruction analyses to analyze the role of the various traits in the evolution of the group. The origin of the group was estimated in the Oligocene, and speciation and shifts in the ancestral ranges, climatic preferences and host-plant preferences were congruent with multiple South American biogeographical and climatic events, especially during the Miocene. These analyses indicate that the evolution of the group was likely initially driven by biogeographic events and that climatic preferences and host plant switches occurred after new regions were colonized. Generally, this work significantly contributes to the systematics of <i>Chalepogenus</i> bees, while providing a framework for building and testing eco-evolutionary hypotheses based on natural history and phylogenetic data. Moreover, it is an important addition to the knowledge of the biogeographic history of South America, highlighting the importance of investigating the ecology and evolution of understudied biodiversity.