Genetic monitoring of at-risk species in Canada: an overview and a case study, the northern leopard frog (Lithobates pipiens) in Western Canada.

Abstract

Genetic assessment and monitoring are critical in evaluating the success of conservation efforts for at-risk species. Genetic assessment can provide valuable information, such as identifying conservation management units and revising taxonomy, which can be used to improve population connectivity and perform translocations. Genetic monitoring helps quantify changes in gene frequencies over time, thus providing feedback for conservation management actions, particularly for at-risk species. In the first part of my thesis, I reviewed the status reports of 788 at-risk designatable units (DUs) listed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), which were available up until 2019. My objectives were to evaluate how many Canadian at-risk species have 1) been genetically assessed and 2) undergone genetic monitoring. My results show that genetic data are available for 50% of DUs, although only 2% of them underwent genetic monitoring, and there is a significant taxonomic bias in the availability of genetic information, with mammals and fishes being over-represented and mosses being under-represented. In the second chapter, I investigated the population genetics of one such at-risk species, the northern leopard frog, Lithobates pipiens, which has undergone a rapid decline in the number of populations in western Canada, particularly in British Columbia and Alberta. The last published genetic research on the populations and DUs of the species in Canada was in 2008, and the Creston Valley population in British Columbia is the last remaining population in the Rocky Mountain DU at the most western limit of the species range. To understand changes in population genetics parameters over time, I compared current genetic diversity from four populations: Creston Valley, Drain K, Prince’s Spring, and Cypress Hills, with 1) data from the Wilson et al. study (2008) at the same locations and 2) the extinct population of Fort Steele, British Columbia. Furthermore, to assess changes in the genetic diversity of the Creston Valley population in British Columbia over time, allelic richness and expected heterozygosity of the population were compared at 3-time points using genotypes from 2000 (Hoffman and Blouin 2004), 2004 (Wilson et al. 2008), and 2019. My results show that the current populations of the species in western Canada are highly genetically differentiated from each other, that genetic diversity declines from east to west, and that the Creston Valley population has likely experienced a population bottleneck. Yet, genetic monitoring of the four northern leopard frog populations shows that both genetic diversity and structure had changed very little between 2004 and 2019. But there was evidence of decline in genetic diversity of Creston Valley population between 2000 and 2019, suggesting that genetic monitoring may need to occur over longer time frames in order to detect meaningful changes in genetic diversity. Overall, my results suggest that management plans and recovery strategies should include genetic data in the conservation of at-risk species. My work also contributes to the recovery efforts of the northern leopard frog, particularly in managing the Creston Valley population.