Climate change will alter Amazonian bumblebees' distribution, but effects are species-specific

Patrícia Nunes-Silva ^1* Andre Luis Acosta ² Rafael Cabral Borges ³ Breno Magalhães Freitas ⁴ Ricardo Caliari Oliveira ⁵ Tereza Cristina Giannini ³ Vera Lucia Imperatriz-Fonseca ⁶

• ¹ University of the Rio dos Sinos Valley, São Leopoldo, Brazil
• ² Institute of Advanced Studies, University of Sao Paulo, São Paulo, São Paulo, Brazil
• ³ Vale Technological Institute (ITV), Belém, Pará, Brazil
• ⁴ Federal University of Ceara, Fortaleza, Ceará, Brazil
• ⁵ Autonomous University of Barcelona, Barcelona, Catalonia, Spain
• ⁶ University of São Paulo, São Paulo, Rio Grande do Sul, Brazil

Understanding how climate change affects the distribution of Amazonian bumblebee species is crucial for conserving this group and the pollination services they provide, particularly for the poorly known Bombus brevivillus and Bombus transversalis. This study evaluated how future climate scenarios may alter the suitable habitats of these species in the Brazilian Amazon, providing insights for targeted conservation efforts. We applied species distribution models using occurrence data from museum records and field collections. Climatic suitability was predicted under the baseline and two future periods (2021-2040 and 2041-2060) using the high-emission scenario (SSP5-8.5) from the latest IPCC report (AR6). Ensemble models were generated using five different algorithms, and the most accurate models were used to identify areas of stability, loss, and gain of suitable habitats. Our results show that B. brevivillus is predicted to lose 41.6% of its current suitable habitat by 2060, with significant reductions in northern and coastal zones. Conversely, B. transversalis will maintain 89.5% of its current range, shifting its distribution westward. New suitable areas may emerge for both species, particularly in the western Amazon, which could serve as future refugia. The projected shifts indicate species-specific responses to climate change, with B. brevivillus being more vulnerable than B. transversalis. These findings emphasize the need for proactive conservation measures to protect critical habitats and mitigate the impacts of climate change on these essential pollinators. Future research should focus on assessing thermal tolerance and habitat connectivity to refine conservation strategies.