Insects, pollen, seeds travel wildlife corridors

In an unusual test of a conservation strategy called wildlife corridors, strips of habitat boosted insect movement, plant pollination, and seed dispersal among patches of the same ecosystem.

Theory predicts that adding such corridors enhances the benefits of otherwise isolated preserves, says Joshua Tewksbury of the University of Washington in Seattle. He and his colleagues tested that strategy in South Carolina pine forests.

At eight locations, the researchers cleared mature vegetation and created open habitat on five 1-hectare plots–arranged as a central plot with four satellites. In each case, a 150-meter-long corridor connected the central plot to one outlier, while the others remained isolated. The unlinked patches had dead-end corridors or additional area so they matched the habitat area of another patch and its connecting corridor. Thus, scientists could distinguish between effects of biological entities’ ease of movement and of extra habitat.

Butterflies, pollen, and seeds all moved most often between the corridor-connected patches, the researchers report in the Oct. 1 Proceedings of the National Academy of Sciences. Variegated fritillary and common buckeye butterflies that the researchers captured, marked, and released in the central patch proved two to four times as likely to show up in connected patches as in unconnected ones.

When researchers placed male holly plants in the center patches, females in connected patches showed an average increase in seed production of nearly 70 percent, compared with that in female hollies in unconnected patches. Also, bird droppings in connected patches harbored more berries from shrubs in the center patches than did droppings in patches not connected to the central patch.

This is the first test of a corridor’s effect on plant-animal interactions, says Tewksbury.

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