May 13 2009

12:00 LSB 2320

David Ackerly
Dept of Integrative Biology, University of California Berkeley


ommon currency to consider problems at a range of temporal and spatial scales. In this seminar I will focus on two aspets of this work: rates of trait evolution, and trait-based community assembly. 1) The concepts of niche conservatism and adaptive radiation have played central roles in the study of evolution and ecological diversification. With respect to phenotypic evolution, the two processes may be seen as opposite ends of a spectrum; however, there is no agreed upon method for the comparative analysis of trait evolution that will clearly identify these contrasting scenarios. I will demonstrate the value of direct measurement of rates of trait diversification as an approach to this problem, and introduce a new unit for the rate of phenotypic diversification: the felsen, in honor of J. Felsenstein. Rates of diversification of three functional traits - plant height, leaf size and seed size - in six woody plant clades (Acer, Aesculus, Ceanothus, Arbutoideae, Hawaiian lobeliads, and the silversword alliance) illustrate the value of these rate-based measures for comparative analysis of niche conservatism and trait diversification. 2) In local communities, studies of the distributions of trait values for co-occurring taxa can provide insight into processes of community assembly. In particular, habitat filtering processes are expected to reduce the range or variance of trait values, while a variety of coexistence mechanisms are expected to increase the evenness or spread of trait distributions. Recent studies in my lab, from coastal California and lowland tropical forests, apply null model approaches to test for non-random patterns of trait distributions in woody plant communities, detecting evidence for both sets of processes.

Recent papers related to part 2 of the talk:
Kraft, N.J., Valencia, R. & Ackerly, D.D. (2008) Functional traits and niche-based tree community assembly in an Amazonian forest. Science, 322, 580-582.
Cornwell, W.K. & Ackerly, D.D. (2009) Community assembly and shifts in the distribution of functional traits values across an environmental gradient in coastal California. Ecological Monographs, 79, 109-126.















































































































































































































































































































































































































































































































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