Male bees sleep in a nest box. Credit: S. Griffin
Recent declines in wild bees have caused significant concern about the loss of biodiversity, pollination services, and food security worldwide. To protect these important pollinators, governments and conservation groups have increasingly focused on programs to restore patches of flowers and other lost habitats.
Though the success of these restoration programs depends on the ability of bees to reestablish healthy populations, little is known about the process by which bees find and nest in newly available habitats. An understanding of bee dispersal and colonization would help land managers better design habitats to encourage rapid bee establishment.
To examine how aspects of habitats such as their connectivity, shape, and resource availability affect bee colonization, our recent study in Ecography uses a long-standing fragmentation experiment called the Savannah River Site Corridor Project in South Carolina. In this experiment, patches of open meadow habitat have been created within a dense forest matrix to form a set of fragmented landscapes, each composed of a single habitat patch in the center surrounded by four other patches differing in shape and connectivity.
Within the center patch of each of these experimental landscapes, we released thousands of solitary bees (the Alfalfa Leaf-cutting bees Megachile rotundata) and studied their colonization of nest boxes placed in the surrounding habitat patches.
View looking down a corridor at the Savannah River Site Corridor Project, a long-standing fragmentation experiment in South Carolina. Credit: S. Griffin
We found that landscape corridors initially increased bee movement into connected habitat patches, but that habitat shape, not connectivity, ultimately determined the number of bees that established in any given patch. Patches with more edge (higher edge-to-area ratio) had more nests and bee offspring than patches with less edge, indicating that bees either select for edgy habitats or are more likely to encounter such habitats during dispersal. In addition, bee colonization increased with higher abundance of flowers from the plant family Fabaceae, our focal species’ preferred food.
In sum, our results show that bee establishment is highly affected by habitat characteristics such as shape and resource availability. In particular, the introduction of landscape corridors or other high-edge elements to restored or created habitats may help bees find and establish nests more rapidly than in more simplified habitats. As interest in protecting bees through restoration continues to grow worldwide, our hope is that practitioners can use this information to design habitats that are quickly colonized by a diverse community of wild bees.
Resources
Griffin, S.R. and Haddad, N.M. 2021. Connectivity and edge effects increase bee colonization in an experimentally fragmented landscape. Ecography 44:1-9.
Goulson, D., Nicholls, E., Botías, C. and Rotheray, E.L. 2015. Bee declines driven by combined stress from parasites, pesticides, and lack of flowers. Science 347: 6229.
Potts, S.G., Biesmeijer, J.C., Kremen, C., Neumann, P., Schweiger, O. and Kunin, W.E. 2010. Global pollinator declines: trends, impacts and drivers. Trends in Ecology & Evolution 25(6): 345-353.
Winfree, R. 2010. The conservation and restoration of wild bees. Annals of the New York Academy of Sciences 1195(1): 169-197.
