Mahurin Honors College Capstone Experience/Thesis Projects



Additional Departmental Affiliation


Document Type



Spider beetles are a poorly known group of North American beetles in the family Ptinidae. Protection of biodiversity requires knowledge of species- and population-level distinctiveness, so data regarding genetic structure of spider beetles can shed light on conservation priorities. Spider beetles in the genus, Coleotestudus, are distributed broadly in the southwestern US. Given their small size and lack of flight, it is presumed that the dispersal capability of Coleotestudus is limited, leading to strong population structure on a small spatial scale. We used a three-enzyme restriction-site-associated DNA sequencing (3RAD) strategy to identify single nucleotide polymorphisms (SNPs) throughout the genome of three species: C. abditus, C. giuliani, and C. ventriculus. We used SNP genotype frequencies to describe genetic structure among populations. Our objective was to use a multilocus SNP dataset to evaluate taxonomic questions in the genus Coleotestudus raised by previous work that used three gene fragments – CO1, 16S, and 28S. We evaluated the following questions stemming from an existing three-gene phylogeny: 1) Are the three sampled species best described as three distinct genetic clusters? 2) Can each species be further subdivided into distinct genetic clusters? 3) Do the clusters revealed by our analysis make sense in a geographic context? Our results suggest the three sampled Coleotestudus species are best described as five genetic clusters (K=5) rather than three (K=3) using both STRUCTURE and DAPC analyses. Our analysis further suggests C. abditus and C. giuliani are each best described by K=1, and C. ventriculus is best described by K=3. Lastly, our analyses reveal that the clusters of C. ventriculus appear to correspond to major biogeographic regions of the southwestern US. Future sampling at a finer geographic scale will help to further explore the patterns of gene flow in spider beetles, particularly among populations of C. ventriculus.

Advisor(s) or Committee Chair

Jarrett R. Johnson, Ph.D.


Biodiversity | Biology | Zoology