Modeling long-term occupancy trends in Indiana bumble bees (Hymenoptera: Apidae)

Area of Science:

• Ecology
• Conservation Biology
• Entomology

Background:

• Bumble bees (Bombus spp.) are vital pollinators facing declines due to climate change and habitat loss.
• Disparities in species' range stability suggest complex responses to environmental stressors.
• Understanding these trends is crucial for effective pollinator conservation strategies.

Purpose of the Study:

• To analyze occupancy trends of nine common Indiana bumble bee species from the early 1900s to 2022.
• To model the effects of temperature, crop richness, and crop extent on bumble bee occupancy.
• To identify factors influencing bumble bee persistence and inform conservation efforts.

Main Methods:

• Utilized historical specimen records from over 35 sources for occupancy modeling.
• Developed two models to assess environmental factors influencing county-level bumble bee occupancy.
• Analyzed trends across nine common bumble bee species in Indiana.

Main Results:

• Occupancy probability increased over time for four species: Bombus bimaculatus, Bombus citrinus, Bombus fervidus, and Bombus griseocollis.
• Higher temperatures significantly reduced occupancy likelihood for Bombus fervidus and Bombus vagans.
• Crop richness and extent did not significantly affect bumble bee occupancy.

Conclusions:

• Future climate warming may lead to differential persistence among bumble bee species, potentially restructuring Indiana's pollinator communities.
• Incomplete recent specimen data (47/92 counties post-1990) underscores the need for expanded statewide sampling.
• Continued monitoring is essential for understanding and conserving bumble bee populations amidst ongoing environmental changes.