How a pitcher plant facilitates roosting of mutualistic woolly bats

Question: How does the pitcher plant Nepenthes hemsleyana facilitate roosting of mutualistic bats? Hypothesis: Pitchers have adaptations that match the shape and body size of small woolly bats. Organisms: The pitcher plant Nepenthes hemsleyana, its dose relative N. rafflesiana, and the woolly bat Kerivoula hardwickii. Field sites: Peat swamps and heath forests in western Brunei Darussalam on the island of Borneo. Methods: We measured various morphological traits of N. hemsleyana that might facilitate bat roosting. We compared these traits with those of N. rafflesiana, which is not visited by bats. We compared the sizes and characteristics of the pitchers with the body sizes of roosting bats. Conclusions: As predicted, aerial pitchers matched the body size of bats and had lower digestive fluid levels than pitchers of a close relative. Thus, small morphological differences between closely related species have caused rapid dietary niche divergence.