Identifying functionally distinctive and threatened species

Abstract

Functional traits determine species responses to environmental change and/or determine species effects on ecosystem functions. When species with distinctive functional traits are threatened, there is a risk that ecosystem properties are also threatened. This is because functionally distinctive species may be those that have irreplaceable roles in an ecosystem and/or those that would be able to survive unusual environmental disturbances. To include functional distinctiveness as a criterion in conservation strategies, we need formal quantification of the degree of distinctiveness and threat a species exhibits. Starting with previous quantification attempts, we develop a framework that links different viewpoints on functional distinctiveness and accounts for all species extinction probabilities. Our framework is particularly relevant at the local scale where species extinctions impact ecosystem functioning and where conservation policies are developed. As a case study, we thus applied our framework to the mammals of Indian dry forests known to be threatened with a drastic decrease in functional diversity. We notably highlight that although some of the functionally distinctive and threatened species we identified, such as the tiger, are charismatic and considered by conservation actions, others are not. This is the case for some rat species and pangolins, whose negative image in the media during the COVID-19 pandemic could be detrimental to attracting public interest in their preservation. From this case study, we note that noncharismatic, less known species that may be key for ecosystems could be revealed by applying our framework to a range of ecosystems and taxa.