Bee movement between natural fragments is rare despite differences in species, patch, and matrix variables

Context

Persistence of organisms in fragmented landscapes often depends on the ability of individuals to move between habitat patches. This movement can be limited by variables of the species, patch, and/or matrix, but we often lack a comprehensive understanding of the relative importance of each of the variables and their interactions. As central place foragers, bees need to move to access resources, but we have a poor understanding of what impacts their movement in fragmented landscapes. This lack of information affects conservation efforts.

Objectives

The primary objective was to understand the effects of species, patch, and matrix variables on bee movement between habitat patches.

Methods

Using the naturally fragmented Ozark Mountain glade ecosystem (Missouri, USA), we marked over 4500 bees in 2017 and 2018. Recapture took place 24 h later. Species, patch, and matrix variables were measured or classified including nesting location, bee size class, distance between patches, nesting resources, canopy cover, and floral resources. Principal components were used for patch and some matrix resource variables in models.

Results

Only 8% of recaptured marked bees moved between habitat patches. Increased movement was observed for larger bees and shorter distances between patches. Bees moved up resource gradients to more rewarding patches unless the matrix provided supplementary resources.

Conclusions

Though bees are often considered highly mobile and able to use nearby habitat patches, the rarity of movement in this natural system highlights the importance of patch and nearby matrix resources for supporting bee communities. While many recent studies have emphasized the species, patch, and matrix variables that may influence bee movement, the overall lack of movement even across high variability in these traits suggests conservation should not expect connectivity to help maintain community diversity.