Phylogenomics, Integrative Taxonomy, and Population Genomics in the Travunioidea (Arachnida, Opiliones, Laniatores)
- Author(s): Derkarabetian, Shahan
- Advisor(s): Hedin, Marshal
- Hayashi, Cheryl
- et al.
My dissertation research utilizes next-generation sequencing (NGS) technology and associated bioinformatics processing to answer systematic and evolutionary questions in Opiliones (harvestmen) at different taxonomic scales, focusing on the Laniatores superfamily Travunioidea and particularly the travunioid genus Sclerobunus. Opiliones are a diverse group of arachnids with over 6500 described species distributed on every continent except Antarctica. Despite relatively high diversity (e.g., more described species than mammals), harvestmen are poorly studied.
This dissertation research has three main projects. The first chapter is a higher-level phylogenetics and taxonomic study of the Travunioidea, a clade of ~80 species of harvestmen distributed throughout the Holarctic. Here I utilized ultraconserved elements (UCE) for phylogenomic reconstruction using multiple types of phylogenetic reconstruction methods. Based on results, a new taxonomic classification is proposed for the Travunioidea, including the identification and diagnosis of a new family, and I reassess the phylogenetic utility of morphological characters used to differentiate and diagnose travunioid taxa. The second chapter focuses on species delimitation of the western North American travunioid genus Sclerobunus. I utilized modern integrative taxonomic methods, using both discovery-based and validation-based approaches by combining morphometrics, mitochondrial genetic data, genitalic morphology, and nuclear genetic data derived from newly developed genes based on a comparative transcriptomics approach. This research resulted in a revision of the genus including synonymy of the genus Cyptobunus, elevation of four subspecies, and the description of five new species. The third chapter is a phylogeographic analysis of Sclerobunus robustus, a species distributed throughout the southwestern United States. A hypothesis-based framework was adopted, where stable habitats (i.e., potential refugia) were identified through ecological niche modeling, and hypotheses regarding genetic patterns associated with these refugia were developed. Hypotheses were tested by using genetic data in the form of loci and SNPs derived from double-digest RAD sequencing methods. Two large refugial regions were identified and population genomic analyses supported the presence of both.