PS 10-89 - Evolutionary isolation of Canadian terrestrial vertebrate species

Background/Question/Methods

Conservation prioritization has become increasingly important as a practical response to on-going biodiversity loss. One tool, evolutionary distinctiveness (ED) is based on a measure of evolutionary isolation which highly scores isolated species who share few close relatives. These isolated species encompass a greater share of the total evolutionary history (in millions of years) of their group and are expected to express non-redundant biological features. The conservation of such evolutionary history helps to ensure the protection of ‘option-value’ offering potential future benefits for humanity, and is now being recognized by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). While Global ED scores have been calculated for several vertebrate taxa, Regional-level ED scores have yet to be calculated for Canadian species, making Canada’s most evolutionarily isolated species unknown. Here we present Regional-level ED scores for all Canadian tetrapods. We updated and pruned global dated phylogenies of all terrestrial vertebrates (amphibians, squamates, turtles, mammals, and birds) down to two sets of phylogenies: (i) only native Canadian species, and (ii) both native species and exotic species introduced to Canada. We then calculated two sets of Canadian ED scores, excluding and including exotic species, respectively.

Results/Conclusions

Canada’s ectotherms (turtles, amphibians, and reptiles) represent the majority of Canada’s most evolutionary isolated species and many rank higher regionally than globally. These taxa are also the most at risk in Canada and so species with populations assessed as at risk by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) represent, on average, more than expected evolutionary history. Interestingly, several exotic species, those introduced to Canada, also have very high regional ED scores. While these species are not considered suitable targets for conservation nor are they eligible for assessment by COSEWIC, they are still a part of Canadian biodiversity and interact with many isolated Canadian species. Given that evolutionary isolation correlates with non-redundant evolutionary history, our lists may provide useful input to conservation agencies engaging in conservation prioritization exercises.