The decision-making process of leafcutting bees when selecting patches

Abstract

Change in land configuration is an important driver of pollinator decline. Understanding patch selection by bees in fragmented landscapes has therefore become imperative to guide the design of habitats that support pollinators and ensure their conservation. This is especially true for solitary bees that make up most 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. In these models, bees used both patch size and patch distance, only patch distance, or chose randomly among patches. When patch size was included, bees could estimate patch resources fully or partially. An experiment with a centre patch, surrounded by four peripheral patches of different sizes and distances from the centre, provided observed transition data to test against predictions derived from each of the models. The alfalfa leafcutting bee, Megachile rotundata, does not move randomly among patches. This bee uses both patch size and isolation distance when selecting a patch but can only evaluate patch resources partially. This knowledge can guide the design of habitats in fragmented landscapes to facilitate solitary bee conservation.

Native Bee Habitat Restoration- Key Ecological Considerations from Recent Literature

“…Floral resources are often unequally distributed across a landscape, and patch size can have a significant influence on bee foraging behavior, especially in the context of increasing habitat fragmentation. Bumble bees and solitary bees consider both patch size and isolation when foraging for resources and estimating patch resource availability (Fragoso et al, 2021;Fragoso and Brunet, 2023). Fragoso & Brunet (2023) found Bombus impatiens Cresson,1863 preferred larger, more closely spaced patches, while Megachile rotundata Fabricius,1787 preferred only closely spaced patches and exhibited no preference on the basis of patch size.…”

“…Bumble bees and solitary bees consider both patch size and isolation when foraging for resources and estimating patch resource availability (Fragoso et al, 2021;Fragoso and Brunet, 2023). Fragoso & Brunet (2023) found Bombus impatiens Cresson,1863 preferred larger, more closely spaced patches, while Megachile rotundata Fabricius,1787 preferred only closely spaced patches and exhibited no preference on the basis of patch size. Although bumble bees may prefer closely spaced patches, they can forage over greater distances than solitary bees.…”

“…For example, an average-sized social bee (2.5mm) has a foraging range of ~3,300 meters whereas a similarly sized solitary bee has a foraging distance of ~1,200 meters (Grüter and Hayes, 2022). Fragoso and Brunet (2023) determined that both solitary and eusocial bees use complex learning to determine which patches to visit. In theory, for all bee species, foraging on large patches located close to their nests would be the optimal foraging strategy.…”

Honey bees exhibit greater patch fidelity than bumble bees when foraging in a common environment

“…Bees can also show preference for some patches, where they visit some patches more frequently than others. Patch size and distance between patches can affect patch selection by bumble bees (Fragoso et al, 2021) and leafcutting bees (Fragoso & Brunet, 2023a). Bumble bees tend to visit larger patches more often than smaller patches, but the impact of patch density is typically stronger than patch size, and the effect of patch size can be overcome when the landscape context varies (Bernhardt et al, 2008; Goverde et al, 2002; Heard et al, 2007; Mustajärvi et al, 2001).…”