Habitat corridors connect fragmented habitats to allow the movement of individuals between otherwise isolated ecological communities. Corridors have been shown to increase biodiversity in habitat patches. Additionally, the size and shape of these habitat patches have been shown to impact organisms due to area requirements and the degree of edge effects in a patch. However, few studies have examined the influence of corridors on the abundance and spatial distributions of species in fragmented landscapes. It also remains unknown whether patch shape and connectivity affects species’ quality of offspring. To look at the effects of corridors on communities, we studied four species of wood-nesting Hymenoptera (wasps and bees) living in habitat patches across replicated experimental landscapes. Each experimental landscape was composed of a center patch of longleaf pine savanna habitat surrounded by four equally sized (1 ha) habitat fragments of different shapes, one of which was connected to the center by a 150 m corridor. The center fragment was enriched with the stable isotope 15N and later measured in captured Hymenoptera. To collect wood-nesting wasps and bees, we used a passive method called trapnesting in which empty nesting resources (trapnests) were left in each habitat patch for a growing season to allow occupation by cavity-nesting Hymenoptera. Following removal of trapnests from the field, we allowed Hymenopteran individuals to emerge to identify, measure, and quantify 15N in all specimens.
Results/Conclusions
We focused our efforts on the four most abundant species captured- Monobia quadridens, Euodynerus megaera, Podium rufipes, and Typoxylon tridentatum- which were ubiquitous in all patches. Potter wasps (Eumeninae) M. quadridens and E. megaera reacted similarly to patch type, with abundance increasing in rectangular shaped patches (M. quadridens χ2= 4.79, p= 0.09; E. Megaera χ2= 28.16, p= 7.6e-7). Mud-daubers (Sphecidae) P. rufipes and T. tridentatum showed the greatest abundance in connected patches (P. rufipes χ2= 8.79, p= 0.01; T. tridentatum χ2= 23.64, p= 7.4e-6). We thereby see the effects of patch type on all four Hymenoptera populations. However, only the potter wasp’s individual offspring were affected by patch shape. E. megaera offspring were significantly larger in rectangular patches (χ2= 8.30, p= 0.01), with M. quadridens following a similar trend (There was no difference in transport of 15N between patch shapes (χ2= 2.74, p= 0.25), suggesting that benefits related to patch shape may be due to a patch’s inherent characteristics rather than their contribution to nutrient transport.