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Dissertation Research:
Functional genetic diversity and pathogen resistance in black-tailed prairie dogs
Field Site: Short Grass Steppe Long Term Ecological Research site; Pawnee National Grassland
Keywords: conservation genetics; disease ecology; immunogenetics
Funding: This material is based upon work supported by the National Science Foundation under Grant No. 0910310.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Black-tailed prairie dog, eastern Colorado.  Photo by Helen Lepper

Wildlife face ever-increasing threats from emerging pathogens, many that also cause disease in humans.  Genetic diversity may play an important role in buffering populations against disease.  The genes encoding the major histocompatibility complex (MHC) of the vertebrate immune system have been widely used to discern relationships between genetic diversity and disease.  However, the relationship between disease and MHC diversity remains unclear, likely because other immune system genes are also important in responses to pathogens and parasites.

Prairie dogs (Cynomys spp.) are social rodents that live in distinct colonies made up of territorial family groups with limited interactions.  Prairie dogs are an important component of North American grasslands, but have declined throughout their range, in part because of the introduced pathogen Yersinia pestis, the causative agent of plague.  I performed a literature search for parasites of black-tailed prairie dogs, and found records for 37 pathogen and parasite species.  Given the potential parasite diversity in black-tailed prairie dogs, evidence of disease-induced decline, their taxonomic relationship to several species of conservation concern, and our previous studies of populations in northern Colorado, prairie dogs are an excellent model for associations between pathogen resistance and functional genetic diversity in mammals. Liz with BIOL 320 student, Benjamin Cole, on the SGS-LTER.  Photo by Amanda Lease
Returning a prairie dog back to its burrow.  Photo by Amanda Lease

The vast majority of association studies in wild vertebrates focus on the relationship between a single pathogen and one or a few MHC genes.  I am going beyond the single-pathogen single-gene approach by investigating the relationship between allelic diversity (heterozygosity) in four functionally different immune system genes and the entire parasite community of black-tailed prairie dogs.
I hypothesize that individuals with greater immunogenetic diversity will have reduced parasite diversity because particular alleles provide pathogen resistance.  Since prairie dog colonies experience periodic plague-induced extinction followed by recolonization, I also expect parasite community diversity will increase through time up to an amount determined by colony size and distance to nearest neighboring colony.

I am live-trapping prairie dogs on several colonies on the Short Grass Steppe Long Term Ecological Research Site, controlling for size, location, and time since the last extinction event.  For each captured animal I am quantifying parasite abundance and diversity, recording standard measures of body condition and relevant immune responses (cell-mediated and humoral), and resolving immunogenetic diversity, compared to neutral markers (microsatellites), using SSCP analysis and sequence data.  All animals are returned to the point of capture.

Black-tailed prairie dog, eastern Colorado.  Photo by Chris Symmes
Thirteen-lined ground squirrel - an accidental capture let loose a few moments later.  Photo by Amanda Lease Conservation genetic studies typically use neutral genetic markers (e.g., microsatellites) to investigate relationships between genetic diversity and fitness.  While neutral markers are valuable in discerning population structure and gene flow, their relationship to fitness has been questioned.  Measuring functional genetic variation related to specific ecological/ evolutionary processes (parasitism) is more relevant in determining a species' ability to adapt to a changing environment.  I hope that results from this research will be useful in developing conservation plans for all five species of prairie dogs.  Marker development for functional genes should also be useful in developing functional genetic markers in other wildlife species.

I am also using existing literature to assemble a database of host-parasite relationships of vertebrate species found on the Shortgrass Steppe Long Term Ecological Research Site in eastern Colorado, in order to explore the relationships between host species interactions, host traits, and the diversity and characteristics of their parasites.

CV                    NR495 Undergraduate Research Experience

Advisor:  Mike Antolin          Antolin Lab Website

Graduate Committee: Lora Ballweber, Tom Hobbs, Geof Givens, Mike Antolin

Prongorn antelope, eastern Colorado.  Photo by Amanda Lease
 
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