PARENT SESSION
Organized Oral Session 20: Disease in ecosystems: Reciprocal interactions between pathogens and ecosystems
Organizer(s): F Keesing, RS Ostfeld, and V Eviner
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 510b, Level 5, Palais des congrès de Montréal

Effects of disease on keystone and dominant species.

Collinge, Sharon^*,1, Ray, Chris¹, Cully, Jack ², ¹ University of Colorado, Boulder, CO, USA² US Geological Survey, Kansas Cooperative Fish and Wildlife Research Unit, Manhattan, KS, USA

ABSTRACT- Keystone species disproportionately affect the abundance and distribution of other species and, because of their central functional role, may significantly influence dynamics of infectious diseases in communities in which they occur. For example, changes in abundance of keystone species due to disease may cause major shifts in community composition and ecosystem function, thereby providing dynamic feedbacks to disease transmission processes. We highlight specific examples of effects of disease on keystone and dominant species, including sea otters in coastal California and prairie dogs in western grasslands. Sea otters are currently experiencing widespread mortality due to parasitic infections. Because sea otters have demonstrable effects on the structure and function of near-shore kelp communities, their population declines due to disease are expected to have pervasive effects on species composition and ecological processes. We highlight research centered on black-tailed prairie dogs, which are highly susceptible to plague, resulting in 95-99% mortality in affected colonies. We explore the possibilities for ecological feedbacks between prairie dogs, other rodent host species, and pathogen dynamics in this system. We use data from several sites throughout the geographic range of the black-tailed prairie dog to suggest how spatial variation in the keystone effect of prairie dogs should translate into spatial variation in disease dynamics. For example, if prairie dog presence shifts species composition toward increased abundance of the putatively most competent host, the deer mouse, then declines in prairie dogs should result in negative feedbacks on local disease dynamics. However, if prairie dogs decrease the relative abundance of other rodent species that are found to be more competent hosts, then declines in prairie dogs due to disease should result in positive feedbacks. Our results show that in certain sites prairie dogs do significantly increase the abundance of deer mice, but in sites with different rodent assemblages, the impact of prairie dogs on rodent community composition differs substantially. We conclude that the relative strength of the keystone effect of prairie dogs across its geographic range will significantly influence disease dynamics in grassland ecosystems.

Key words: disease, plague, keystone species, prairie dogs