Degree
Doctor of Philosophy (PhD)
Department
Biological Sciences
Document Type
Dissertation
Abstract
In mountain ranges like the Andes, avian speciation has traditionally been attributed to divergence in geographic isolation. However, as I point out in Chapter 1, recent genomic studies suggest that divergence coupled with occasional gene flow may also be a key factor. In my dissertation, I investigate the processes responsible for the high species richness and phenotypic diversity of birds in montane regions. Using genome-wide data, I reconstruct the evolutionary history of flowerpiercers (genus Diglossa), a group of nectar-feeding birds in the tanager family (Aves: Thraupidae). The evolutionary history of these species, which are confined to mountainous areas and exhibit notable geographic variation, is not well understood due to the lack of genomic data for the clade. My research aims to establish Diglossa as a model group for studying speciation in tropical montane regions by expanding genomic resources for them, including the addition of high-quality tissue samples collected during expeditions to Peru and Bolivia.
In Chapter 2, I present the first high-quality reference genome for Diglossa brunneiventris, created using long-read sequencing techniques to achieve a near-chromosome-level assembly. This genome serves as a foundation for later chapters, where I use it to map reads, extract sequences, and explore the evolutionary history of the group. Chapter 3 employs phylogenomic data from ultraconserved elements (UCEs) to construct a population-level phylogeny of Diglossa, investigating how sample type can produce misleading phylogenomic results, especially at the shallow population-level. In Chapter 4, I explore the influence of gene flow within the D. carbonaria complex using restriction site-associated DNA sequencing (RADseq), revealing previously undetected gene flow. Chapter 5 focuses on the narrow contact zone between D. humeralis and D. brunneiventris in northern Peru. Using genome re-sequencing data, I demonstrate that hybridization likely occurs despite limited phenotypic intermediates, and I identify genetic loci which may contribute to species boundaries and plumage color between the two species. Finally, Chapter 6 synthesizes the findings of the dissertation within the broader context of how genomic data has transformed our understanding of avian speciation in the high Andes and Neotropical mountain regions.
Date
4-2-2025
Recommended Citation
Hiller, Anna, "Speciation in the Andes Examined Through the Evolutionary History of Diglossa Flowerpiercers" (2025). LSU Doctoral Dissertations. 6754.
https://repository.lsu.edu/gradschool_dissertations/6754
Committee Chair
Faircloth, Brant C.