Phylogeography of wood frogs (Rana sylvatica)
The wood frog is one of the most widely distributed amphibians in North America, and the only frog species that occurs beyond the Arctic Circle (Martof & Humphries 1959). My objectives are to use genomic sequencing tools to reconstruct the evolutionary history of the wood frog’s range, and to explore variation between populations at large and small scales along latitudinal and thermal gradients.
In order to represent the full range of the wood frog, I am conducting fieldwork to collect new tissue samples, but I’m also using natural history museum collections as a resource for existing tissue samples. I have also had the privilege to work with incredible folks across the United States and Canada who collected samples from various regions such as Galena, Alaska, and Inuvik and Norman Well in the Northwest Territories, Canada.
Image: First wood frog that I sampled during my summer 2021 fieldwork trip along the Ambler and Kobuk rivers in Alaska. It was an exciting day!
Extreme freeze tolerance
Wood frogs are one of very few vertebrate species that use freeze tolerance as a strategy for overwintering. Instead of avoiding freezing altogether, wood frogs seek shallow hibernaculum beneath the soil and leaf litter and are adapted have ~70% of their body water frozen. Their bodies accomplish this by producing cryoprotectants–molecules such as glucose and urea–that protect their cells from the stressful freezing process. Come Spring, wood frogs thaw, emerge from their hibernacula and make their way to the ponds to begin breeding!
Image: a frozen adult wood frog sitting on a bed of sphagnum moss and tissue paper. I collected this frog in early Spring and performed this freezing experiment in the lab. This frog survived freezing at a temperature of -2.5 oC for 48 hours!
Adaptive variation of Chinook Salmon
As part of the 2020 Landscape Genetics Distributed Graduate Seminar, I had the opportunity to collaborate on a project focused on adaptive variation in Chinook salmon. My colleagues and I were curious about the influence of environmental conditions that Chinook Salmon experience along their migration corridors, and at spawning sites. Specifically, we asked whether selection in this species is primarily driven by the migration corridor environment or by the spawning site environment.
We performed genome-environment associations using millions of SNPs from whole-genome resequencing, and we found that migration corridor variables may be more influential on Chinook salmon genetic variation compared to spawning site variables
I presented our findings in the 2021 meeting of the International Association for Landscape Ecology – North America. This work is accepted for publication pending minor revisions in Ecology & Evolution as of July 2021.
Image: map of our seven study sites and sample locations in the Columbia River Basin.