PARENT SESSION
Oral Session # 1: Ecological Theory I: Theory; Scaling.
Presiding: M Pascual
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 100.

Local-regional diversity relationships: Immigration, extinction and scale.

He, Fangliang^*,1, ¹ Canadian Forest Service, Victoria, BC, Canada

ABSTRACT- While local processes (e.g., competition, predation and disturbance) presumably cause species exclusion and thus limit diversity in a community, regional processes (e.g., historical events, immigration and speciation) are assumed to provide source species for colonizing and thus enrich a local community. Ecologists desire to distinguish between these two sets of processes using evidence for local assemblage saturation, but such efforts have been controversial and are antithetical to the fact that local diversity bears an imprint of both. Here we examined the local-regional species richness relationship from the perspective of the theory of island biogeography and developed a model that unified assemblages ranging from saturated to unsaturated. The model shows that there is no dichotomous division between saturated and unsaturated assemblages, the degree of saturation of an assemblage is determined by the magnitude of the difference between colonization and extinction rates and sampling scale. Saturation will result if extinction rate is large relative to colonization rate, while a lack of saturation will result if colonization rate is relatively large. Because sampling scale is also predicted to have a similar effect on the shape of the local-regional relationship to that of immigration and extinction, the relationship must be interpreted with caution and in order for it to be useful for inferring ecological processes, it is necessary to collect data on sampling scale in any such study.

Key words: global processes, macroecology, local processes, species diversity