PARENT SESSION
Oral Session # 5: Biogeography I: Community Structure and Diversity.
Presiding: B Enquist
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 104.
Community dispersal in a hierarchically-structured landscape and the relationship between local and regional diversity.
Cadotte, Marc*,1, Fukami, Tadashi1, 1 Complex Systems Group, Knoxville, Tennessee
ABSTRACT- Dispersal is thought to increase local (alpha) diversity and decrease among-habitat (beta) and regional (gamma) diversity because extinction-prone species will maintain higher local abundances, show prolonged persistence time, and occupy more regional sites due to a rescue effect. However, dispersal normally occurs at multiple spatial scales in a hierarchically structured system, posing a problem in defining local and regional scales for understanding diversity. We used freshwater microcosm landscapes each consisting of three metacommunities each containing three local communities to examine the role of dispersal and its scale dependence. Each local community was initially stocked with 8 of 14 potentially competing prey species and 2 of 3 possible predators. We manipulated dispersal into three treatments: I) dispersal within and among metacommunities, II) within metacommunities only, and III) no dispersal. At the local community scale we found that alpha diversity was not strongly affected by dispersal. However, beta and gamma diversity were both lowered by dispersal. At the metacommunity scale the same pattern was apparent, and higher-scale dispersal (i.e., among metacommunities) did not affect patterns of diversity between landscapes I and II. Dispersal at the local-level appeared to be the most important factor affecting beta and gamma diversity. Persistence time decreased significantly with dispersal, and isolated populations were less prone to extinction. A few species benefitted greatly from dispersal and colonized all habitats. Overall, we attributed these patterns to the movement of a single predator which was able to structure local communities to a very similar state. Our results suggest that local-level processes are important in structural patterns of diversity and that the scale at which dispersal occurs need explicit consideration in understanding its effects on local and regional diversity.
Key words: predation, community structure, dispersal, microcosm