EAPSI: Making Sense of Exceptional Diversity: Coexistence of Many Species in the Mammal Communities

Nations Jonathan, Baton Rouge LA

Investigators

Abstract

Life on the planet is not evenly distributed. Though species richness often peaks in the tropics, biological diversity is remarkably wide-ranging at both global and local scales. The tropical oceanic island of Sulawesi, Indonesia contains exceptionally high biodiversity, but the murine rodent (rats and mice) fauna is especially remarkable. Some montane communities containing up to 23 co-occurring murine species, making these the richest communities of closely related mammals on the planet. However, despite indistinguishable habitats, some montane communities contain as few as 10 species. The theory of adaptive radiation predicts that, in order to coexist, species in a community must not rely on the same resource, but instead partition resources through variation in diet, habitat, or both. To understand how resources are partitioned, this collaborative project will generate high-resolution morphological and dietary data from museum specimens in the lab of Dr. Kevin Rowe, Curator of Mammals at Museum Victoria. With these data, this project will test the prediction that members of the most species rich communities are existing on a greater diversity of resources from a wider variety of habitats than the less species rich communities. This project represents an exceptional opportunity for international collaboration while providing evidence that will illuminate how some communities are so diverse, an issue that has puzzled biologists since the earliest days of evolutionary thought. The theory of adaptive radiation predicts that adequate ecological space must exist for closely related species to co-occur. Calculating the ecological volume occupied in a community can explain how resources are partitioned. The murine rodent (rats and mice) fauna of Sulawesi is remarkable, with some montane communities containing up to 23 co-occurring species. However, this diversity is not distributed equally across the island, and some montane communities contain as few as 10 species. This variation provides a natural experiment in community assembly with the potential to illuminate how these hyperdiverse communities originate and are maintained. This collaborative research will use natural history collections at Museum Victoria to determine the ecological niche volume filled by montane communities across Sulawesi, testing the prediction that local community niche volume will be positively correlated with species richness. Niche volume will be quantified using a novel combination of high resolution skeletal imaging (uCT scans), isotopic analyses of diet, and the structure of digestive tracts, providing an integrated view of how Sulawesi rodents exploit available resources. This collaborative project will determine whether rich communities pack more species into the same ecological volume, or expand total volume, potentially resolving a long-standing, general question in evolutionary ecology. This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by NSF and the Australian Academy of Science.