Species interactions at range boundaries

Meghan S Lout, Purdue University

Abstract

Patterns of ecological segregation by geographic range, habitat or substrate have stimulated much interest in forces limiting species distributions. Sharp truncation of species ranges associated with the presence of similar species has especially generated research into the importance of behavioral interactions. Understanding species interactions at range boundaries is an important first step in understanding how species will respond to the large-scale changes associated with climate change. I ask whether interspecific interference is a mechanism underlying patterns of high beta diversity and range abutment, and if vocalizations play a role in range limitation of bird species in the Tilarán mountains of Costa Rica. To test these hypotheses, I studied two species of nightingale-thrushes (Catharus mexicanus and C. fuscater) whose ranges abut in a narrow ecological transition zone at the lower edge of cloudforest. I also analyzed 4,614 of their songs to investigate whether acoustic patterns in the songs of individuals in the replacement zone suggest interference. Territory mapping revealed mild interspecific territoriality, while spectral analysis of vocalizations suggests vocal divergence. C. mexicanus vocalizations include fewer acoustic components that match components in the C. fuscater repertoire when heterospecific neighbors are also vocalizing. Experimental acoustic challenges by a collaborator also support the conclusion that mexicanus individuals avoid conflict with fuscater neighbors. Results suggest that species interactions at range boundaries could contribute to local range limitation, and that such interactions could be important in impending community reorganization.

Degree

M.S.

Advisors

Rabenold, Purdue University.

Subject Area

Ecology

COinS