COS 76-4 - Species trade-offs explain more than just intermediate disturbance patterns

Wednesday, August 10, 2011: 2:30 PM
9C, Austin Convention Center
C.M. Tucker, Instaar, University of Colorado, Boulder, Boulder, CO and Marc W. Cadotte, Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada

The immense diversity of species, and the apparent coexistence of species with differing competitive abilities, remains a central paradox in community ecology. The role of disturbance in driving coexistence is a familiar explanation for high diversity in many regions. In high-diversity Mediterranean heathlands such as the Cape Floristic Region (CFR) in South Africa, recurrent fires may drive coexistence mechanisms. However, the dominant explanation of diversity-disturbance relationships, the “Intermediate Disturbance Hypothesis” (IDH), has not been supported in the CFR. Using data from the fire-prone, hyperdiverse Cape Floristic Region of South Africa, we assess whether diversity-disturbance relationships are a function of the frequency of post-fire regeneration strategies in the species pool.


A post-fire regeneration trade-off (reseed versus resprout) determined species responses to fire frequency, however a specific relationship between disturbance and diversity (such as the unimodal relationship predicted by the IDH) did not exist. Instead, the proportion of seeding and resprouting species in the species pool predictably determined the shape of the relationship between fire frequency and species richness. This single complicating factor – the incidence of a tradeoff in the species pool – allows a single relevant tradeoff to produce multiple, predictable patterns of response to disturbance.

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