The decision-making process of leafcutting bees when selecting patches

Authors: FRAGOSO, FABIANA - Orise Fellow; Brunet, Johanne

Submitted to: Biology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2023
Publication Date: 2/15/2023
Citation: Fragoso, F., Brunet, J. 2023. The decision-making process of leafcutting bees when selecting patches. Biology Letters. 19 (2). https://doi.org/10.1098/rsbl.2022.0411.
DOI: https://doi.org/10.1098/rsbl.2022.0411

Interpretive Summary: Habitat fragmentation is an important driver of pollinator decline. In order to ensure pollinator conservation, we need a better understanding of the process by which pollinators select patches in fragmented landscapes. Such knowledge can guide the design of habitats that support pollinators and ensure their conservation. Because solitary bees make up the great majority of bee species in the world, it is particularly important to understand their patch selection process. In this study, we examined the patch selection process of the solitary bee, Megachile rotundata, an important managed pollinator in alfalfa seed-production fields. To elucidate the process by which this solitary bee selected patches, we tested the predictions of four distinct models of patch attractiveness against empirical data. These models differed in the role of patch size and isolation distance in the selection process. The empirical data represented bee transitions from a center patch to each of four peripheral patches of two different sizes and distances from the center. Results indicated how the alfalfa leafcutting bee uses both patch size and isolation distance when selecting a patch, but can only evaluate partial resources in a patch. Our approach successfully identified how leafcutting bees selected the next patch they move to, and future work should determine whether the process of patch selection varies among solitary bee species. Such knowledge can guide the design of habitats in fragmented landscapes to facilitate solitary bee conservation. As patch selection can affect gene flow, knowledge of the patch selection process of specific bee species can also guide the design of agricultural landscapes to limit gene flow. This information will be of interest to researchers and the general public interested in solitary bee behavior and conservation; to regulatory agencies, farmers and the industry dealing with GE crops and with bee conservation.

Technical Abstract: Change in land configuration is an important driver of pollinator decline. Understanding patch selection by bees has therefore become imperative, since knowledge of patch selection in fragmented landscapes can guide the design of habitats to support pollinators and ensure their conservation. This is especially true for solitary bees that make up the majority (over 85%) of bee species in the world. To elucidate the decision-making process of a solitary bee when selecting patches, we tested four models of patch attractiveness that differed in the role of patch size and isolation distance in the selection process. An experiment with a center patch, surrounded by four peripheral patches of two different sizes and distances from the center, provided observed bee transition data to test against the predictions derived from each of the four models. The alfalfa leafcutting bee, Megachile rotundata, uses both patch size and isolation distance when selecting a patch, but can only evaluate partial resources in a patch. This solitary bee does not move randomly among patches; it utilizes spatial information over patchily distributed resources. This knowledge can guide the design of habitats in fragmented landscapes to facilitate solitary bee conservation.