Does climate change influence the current and future projected distribution of an endangered species? The case of the southernmost bumblebee in the world

Abstract

Introduction: Cold-adapted bumblebees are vulnerable to climate change (CC). South American Bombus dahlbomii, the southernmost bumblebee worldwide, has strongly declined since the 1990s and may be particularly susceptible to current and future CC. Aims/methods: We asked (1) whether current CC had a role in the observed decline of this species and (2) how projected CC would affect the future distribution of B. dahlbomii. We used a comprehensive record of occurrences for B. dahlbomii and species distribution models (SDMs) to build maps of (1) predicted current climatic suitability using pre-1990s and post-1990s occurrences, and (2) projected current and future climatic suitability under future (2080–2100) RCP 8.5 scenarios predicted by the 5th IPCC Report. Results and discussion: SDMs did not show changes in species climatic suitability pre-1990 vs. post-1990, suggesting no significant role of CC on the observed decline of the species at this time scale. However, a moderate range reduction of 13% and 14% of the ~ 0.041º grid cells was predicted by 2080–2100 under the 70% and 100% consensus models, respectively. Implications for insect conservation: Identifying the threats to B. dahlbomii allows for prioritizing conservation efforts. Short-term threats imposed by invasive bumblebees deserve urgent attention. The potential synergies between this threat and CC need to be understood to better predict the fate of this species. Binational cooperation should guarantee connectivity between climatically suitable areas in Argentina and Chile.