PARENT SESSION
Oral Session # 59: Mutualism - Parasitism II: Animal and Insect.
Presiding: L Cochran-Stafira
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 203.
Spatial structure affects dynamics in a treehopper - ant mutualism.
Yee, Susan*,1, 1 University of Chicago, Chicago, IL, 60420
ABSTRACT- Although mutualisms are ubiquitous in nature, formal models of mutualisms have seen limited development and application. Simple models suggest mutualisms are prone to extinction, making it difficult for mutualisms to become established from small numbers of individuals. Reaction-diffusion models indicate spatial structure may be a stabilizing mechanism in mutualism dynamics. It is unclear, however, whether space is a mechanism preventing extinction in natural populations. I used a reaction-diffusion model of mutualist dynamics to explore how aspects of spatial structure, including dispersal ability and initial spatial distribution, are likely to affect species interactions. Predictions were tested experimentally in a naturally occurring ant-treehopper mutualism. I assessed the effects of dispersal ability on treehopper dynamics within a metapopulation of treehopper colonies tended by a single ant colony. I manipulated treehopper movement between plants in concert with ant access to treehopper colonies. Results indicate that a reduction in treehopper dispersal significantly reduces both treehopper population growth rate and the number of plants within each metapopulation occupied by treehoppers. Effects of treehopper dispersal were strongest when ant access to each colony was low. Clearly, the ability of treehoppers to colonize plants and the ability of ants to locate treehopper colonies are important determinants of the dynamics in this mutualistic interaction. The stability of mutualisms in natural systems likely depends on the colonization abilities of each species, as well as the initial spatial distribution of each species and the availability of habitat.
Key words: mutualism, spatial ecology, modeling