Date of Award


Degree Type


Degree Name

Master of Science




Biology (MS)

First Advisor/Chairperson

Kurt Galbreath


The opening and closing of the Bering Land Bridge due to Pleistocene climate fluctuations facilitated the exchange of taxa between the Palearctic and Nearctic. While many studies have worked toward elucidating the role of Beringia in assembling northern faunas, relatively little work has focused on parasites. Here I examine the number and direction of transberingian colonization events within the Holarctic tapeworm genus, Arostrilepis Mas-Coma & Tenora, 1997. I performed maximum likelihood and multi-locus coalescent phylogenetic reconstructions using mitochondrial and nuclear DNA sequences. Biogeographic ancestral range estimations were conducted on the resulting species phylogeny. My systematic reconstructions reveal as many as 16 Arostrilepis lineages that could represent previously undescribed species-level diversity. Biogeographic estimates strongly indicate that Arostrilepis experienced at least four eastward transberingian dispersals associated with Microtus, Myodes, and Lemmus hosts. Comparing the Arostrilepis colonization history with the pattern of its host associations shows that host-switching is prevalent in its history particularly following the Nearctic colonization associated with Microtus voles. Evidence also suggests that during the colonization event associated with lemmings, the direction of Arostrilepis colonization may have been counter to that of its hosts. These results highlight the complex history of faunal assembly associated with Beringian mammal-parasite assemblages.

Access Type

Open Access

Included in

Biology Commons