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William B. Batista

Willie is adjunct professor at the  University of Buenos Aires, Facultad de Agronomía. His research program is aimed at understanding the structure and dynamics of natural plant populations and communities. Most of the current work in his lab is related to the case study of El Palmar National Park (31° 55'S, 58° 16'W), Argentina, an 8500 ha protected area of temperate savanna. The research program is based on the idea that, as a consequence of past and present human influence, most natural areas require energy subsidies to preserve their natural structure and dynamics. Effective application of such subsidies is contingent on how well we understand the particular ecosystem and its driving factors. In particular, Willies research focuses on the roles of substrate properties and disturbances on the structure and dynamics of plant communities and plant populations present in different parts of the landscape.
During his Ph.D. at the Louisiana State University, Department of Botany, he worked on demography of a shade- tolerant tree (Fagus grandifolia) in a hurricane-disturbed forest, and on the responses of tree populations to hurricane disturbance in old-growth southern mixed hardwood forests. Recently he became interested in more theoretical questions of time-scale dependence in matrix population models.

I met Willie first 1998 in Buenos Aires at "el Turco", a bar at the corner of the IFEVA where people usually have lunch. Later some of his students attended my post graduate course on spatial pattern analysis and we started to collaborate in point-pattern analysis of data from El Palmar National Park. During my visits in Buenos Aires we spend together with María many nights at the Colon, Tango concerts, and art exhibitions. I invited Willie to spent four weeks as guest scientist at the OESA. During his stay at the OESA Willie gave an exciting talk on:

Time-scale dependence in matrix population models

William B. Batista, and William J. Platt

In matrix models, elasticities measure the proportional contributions of different demographic processes to λ, the asymptotic rate of population growth. We prove that elasticities change with the time step of the model and that the contribution of stasis to λ decreases exponentially with increasing time step. We demonstrate how increasing the time-step results in vanishing contributions of stasis and growth and increasing contributions of fecundity using American beech and loggerhead turtle populations. We thus reconcile matrix model predictions that population growth is most limited by mortality with predictions from ecological studies that population growth is regulated by recruitment limitation.