COS 53-3 - Effects of severe wildfire on peripheral populations of an at-risk species

Background/Question/Methods

Fire is a natural part of the disturbance regime of many ecosystems. However, the increasing frequency and unprecedented severity of wildfires in recent times has the potential to negatively impact sensitive species. These effects may be more pronounced at the edges of species’ ranges where population sizes may be naturally small. Here, we examine the impacts of a particularly severe wildfire on peripheral populations of the long-toed salamander (Ambystoma macrodactylum), a species of conservation concern in western Canada. We used a long-term monitoring dataset and a before-after, control-impact design to investigate the immediate impacts of the fire on breeding-pond occupancy. We paired this with an analysis of a reduced representation sequence (ddRAD) dataset from tissues collected before and after the wildfire to assess a) the genetic uniqueness of populations impacted by the fire relative to other parts of the species’ range and b) the potential for the wildfire to have impacted genetic diversity and thus the evolutionary potential of these populations.

Results/Conclusions

Formal occupancy analysis suggests that the wildfire had limited impact on breeding-pond occupancy, despite its severity and timing with respect to a critical life-stage transition. At the same time, at least one population in the burn zone seems to have been entirely lost and, although not statistically significant, we observed a downward trend in occupancy in the burn zone following the fire. Genetic results based on an analysis of 40 170 loci suggests these populations are highly distinct from other populations in western Canada and the USA and represent a substantial part of the range of a unique genetic subspecies. Thus, declines in this region have the potential to erode broader measures of genetic diversity in this taxonomic group. In this talk, I will compare and contrast results from our occupancy analysis with a genetic assessment of population bottlenecks and changes in site-level diversity in order to discuss the potential for the fire to have legacy effects on this system that are not readily apparent in an analysis of occupancy alone.