Decoding the Past: Evolutionary History of North American Deer Mouse Populations on the Gulf Islands
Graduation Term
2024
Degree Name
Master of Science (MS)
Department
School of Biological Sciences
Committee Chair
Pirmin Nietlisbach
Abstract
Anthropogenic habitat fragmentation is increasing the number of small and isolated organismal populations, and the long-term effects of these recent isolations are not well understood. Small populations are at increased risk of extinction thus it is essential to identify populations that have been isolated over long time periods to use as model systems to study consequences of isolation. Besides understanding genetic consequences, isolated populations may also serve as natural systems to study morphological changes in populations that have independent evolutionary trajectories. Investigating island populations may help in the discovery of long-term isolated populations that may be experiencing morphological changes as well. Island populations of small land vertebrates frequently exhibit insular gigantism, presenting with larger body sizes in comparison to mainland counterparts. I studied historic population isolation and presence of insular gigantism of North American Deer Mice (Peromyscus maniculatus) in the Gulf Islands of British Columbia, Canada. These islands were isolated after sea-level rise following the Pleistocene ice age. I hypothesized that the order and timeline of island separation, due to a rise in local sea level, affected the phylogenetic relationship of island populations, through genetic isolation. Furthermore, I expected to find evidence of island gigantism in these isolated island populations. I live trapped Deer Mice on nine of the Gulf Islands, as well as the mainland and took tissue samples for DNA extraction and recorded body mass. Samples were sequenced at low depth (2x, n=160) and high depth (20x, n=10). Analyses indicate genetic isolation of the smaller island populations as well as mainland populations. Furthermore, evidence from high depth samples indicate population divergence of several thousand years. I also found presence of insular gigantism in the Gulf Islands system. Examining the evolution of island body size is becoming increasingly imperative as populations experiencing gigantism and dwarfism are under greater extinction threat. Island populations with these morphological extremes may be under even greater threat if they are also small and isolated. Understanding the evolutionary history of these populations will provide insight into future work regarding the evolution of small, isolated populations and how some have persisted through time.
Access Type
Thesis-Open Access
Recommended Citation
Berg, Rachel Ann, "Decoding the Past: Evolutionary History of North American Deer Mouse Populations on the Gulf Islands" (2024). Theses and Dissertations. 1885.
https://ir.library.illinoisstate.edu/etd/1885
DOI
https://doi.org/10.30707/ETD2024.20240618063947871840.999993