Degree
Doctor of Philosophy (PhD)
Department
Department of Biological Sciences
Document Type
Dissertation
Abstract
Uncovering the genetic components of adaptation is fundamental for understanding evolution by natural selection. Recently, genomic analyses have been applied to an increasing number of non-model organisms to better explain the evolution of biodiversity. I applied analyses of whole genome datasets to better understand the evolutionary history of Sulawesi white-toothed shrews (genus Crocidura) and phenotypic evolution in the hero shrew, Scutisorex somereni.
Sulawesi is a large Indonesian island located in the Wallacea biogeographic region of the Indo-Australian Archipelago. Many lineages that colonized Sulawesi have undergone in-situ diversification, resulting in a high number of endemic species arising over relatively short geological timescales. One such lineage is Crocidura, which comprises 20 endemic species.
Previous work describing the diversity of Crocidura in Sulawesi used molecular and morphological analyses and found well-supported species boundaries. However, interspecific relationships were less resolved. To better understand evolutionary history in Sulawesi Crocidura, I assembled a large, whole-genome variant dataset that I used to estimate phylogenies. I inferred a well-supported phylogeny for Sulawesi Crocidura which is a critical tool for understanding evolution in this clade.
Using the variant dataset together with the well-supported phylogeny, I next sought to characterize the evolutionary processes occurring in Sulawesi Crocidura, an exemplar system for studying rapid radiation. I found a signal of low-magnitude geneflow, which was widespread and statistically significant. I hypothesize that parallel speciation is the process that has resulted in high species richness but relatively conserved phenotypic diversity in Sulawesi Crocidura.
Scutisorex somereni has what is perhaps the most unique axial skeleton of all vertebrates. Given the distinctiveness of this trait, there is a need to understand the evolution of underlying genomic elements. Using a comparative genomics approach comparing S. somereni to 30 other mammal species, I found HOX genes that were under positive selection. This highlights at least one plausible evolutionary mechanism contributing to this extreme phenotype.
Overall, my dissertation demonstrates how analyses of genomic datasets can be used to understand evolution in non-model species that are difficult to observe.
Date
10-31-2025
Recommended Citation
Chipps, Austin S., "Genomic Insights to Shrew (Mammalia: Soricidae) Evolution: From Rapid Radiations to Morphological Innovations" (2025). LSU Doctoral Dissertations. 6931.
https://repository.lsu.edu/gradschool_dissertations/6931
Committee Chair
Esselstyn, Jacob A.