PARENT SESSION
Oral Session # 92: Biogeography IV: Dispersal.
Presiding: J Choo
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 104.

Biodiversity consequences of directed versus random movement patterns.

Armsworth, Paul^*,1, Roughgarden, Joan¹, ¹ Stanford University, Stanford, California

ABSTRACT- Most ecological and evolutionary theories of spatial dynamics assume organismal movements are unconditional, non-directional and occur at constant rates. We explore an alternative representation, in which movement is viewed as an adaptive response of a phenotype to varying environmental conditions. In this representation of 'directed' movement, we assume movement stimuli derive from local gradients in fitness and that movements are oriented along these gradients. We compare the implications of the two movement assumptions for speciation and biodiversity patterns. Random movement results in high alpha-diversity but minimal beta-diversity. Too much random movement results in a loss of regional diversity. Directed movement maintains biodiversity through a spatial partitioning of species. Therefore, with directed movement, alpha-diversity is low, and beta-diversity is much higher. There is no cost of vagility for regional diversity with directed movement. We consider speciation by reinforcement. An intermediate dispersal principal applies for speciation with random movement. Directed movement precludes speciation in undisturbed environment, but speciation is possible with directed movement when there are infrequent environmental disturbances.

Key words: Movement behaviour, Speciation, Dispersal, Biodiversity patterns