Constraints on dispersal evolution
Across taxa, individuals vary in how far they disperse, with most individuals staying close to their origin, and far fewer individuals dispersing long distances. Despite their rarity, long-distance dispersal events contribute critically to range shifts, invasions, and population persistence. I am using the stream salamander Gyrinophilus porphyriticus to investigate the causes and consequences of variation in dispersal distance. Using direct dispersal data from the field (via capture-mark-recapture surveys), I have identified a morphological phenotype linked to variation in dispersal distance. Interestingly, this morphological specialization appears to come at a cost to individual swimming performance. Such trade-offs may help to explain the rarity of long-distance dispersers and provides mechanistic insight into proximate factors maintaining variation in dispersal distance in natural populations.
Causes of variation in dispersal distance
Dispersal is expected to evolve as an adaptive mechanism to optimize individual fitness across the landscape. While there is evidence that active dispersers base emigration decisions (i.e., stay vs. leave) on perceived costs associated with environmental variation and inbreeding, it is less well understood how and whether these same factors influence dispersal distances– a more comprehensive measure of dispersal. I am specifically interested in testing whether local or large-scale patterns of environmental variation - matching fixed and conditional models of dispersal evolution - better predict variation in dispersal distances. I am also using population genomic data (ddRADSeq) to evaluate whether dispersal occurs at scales large enough to effectively reduce inbreeding risk in G. porphyriticus. These projects will shed light on the relative importance of varying selective pressures influencing dispersal distances.
Population genetic structure and disease prevalence in boreal toads
Amphibians are more threatened than any other vertebrate class, in part because of life history characteristics that lead to patchy distributions and geographically isolated populations. Additionally, the fungal pathogen Batrachochytrium dendrobatidis (Bd) has been linked to amphibian declines worldwide. My master’s research explored factors that influence population isolation, patterns of genetic variation, and disease prevalence in boreal toads, a species that is declining in portions of its range. I conducted this work in Glacier National Park, Montana, and found that mountain ridges are barriers to gene flow and that high elevation populations exhibited reduced genetic variation. Surprisingly, more heterozygous individuals were more likely to be infected with Bd, suggesting that dispersal may facilitate the spread of the disease. Read more about this work here.