Abstract
Zanthoxylum section Tobinia is a diverse group of trees and shrubs in the Caribbean. Very little is known of its evolutionary relationships and biogeography. There is a high degree of taxonomic uncertainty, especially concerning the status of Endangered Z. thomasianum and its relationship to the Z. punctatum taxonomic complex. Furthermore, gaps in our knowledge of distribution, genetic diversity, and ecology in Z. thomasianum hinder effective conservation.This research aims to integrate target enrichment genomic approaches with
morphometric analysis, demographic, and ecological data to fill these knowledge gaps. Firstly, DNA sequence data is used to reconstruct a phylogenetic tree of Zanthoxylumsection Tobinia to understand the relationships among the taxa in this group. Combined with morphometric analysis and distribution data, species delimitation is investigated. Second, single nucleotide polymorphisms from the target enrichment dataset are used to further refine species delimitation in the Z. punctatum complex. Genetic diversity, inbreeding and population differentiation in Z. thomasianum is determined and, combined with demographic field data, used to inform a conservation management plan. Finally, the phylogeny of Z. section Tobinia is dated and the historical biogeography of the
group is reconstructed using maximum likelihood modelling.
Phylogenetic analysis confirms monophyly of Z. section Tobinia, but also that existing classifications do not adequately describe diversity in the group. Phylogenetic, population genetic, morphometric, and geographic evidence supports the recognition of five new species in Puerto Rico. Z. thomasianum is shown to exhibit strong population genetic structure in the Virgin Islands and low levels of inbreeding. Populations are shown to be inadequately covered by protected areas, and in-situ and ex-situ conservation is recommended to prevent further loss of genetic diversity.
Target enrichment is shown to be a highly effective tool for addressing knowledge gaps at a variety of scales, from evolutionary relationships and history at broad spatial and temporal scales, to genetic diversity structure at the population level. This research informs our understanding of patterns and processes shaping biodiversity in the Caribbean hotspot and guides its conservation.
| Date of Award | 12 Sept 2025 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Frank Schubert (Supervisor), Jan Viruel (Supervisor) & Steven Dodsworth (Supervisor) |