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Process-based modeling of species richness and niche shifts among woody formations in South America

Grant number: 12/06005-1
Support type:Scholarships abroad - Research Internship - Post-doctor
Effective date (Start): September 01, 2012
Effective date (End): May 31, 2013
Field of knowledge:Biological Sciences - Ecology
Principal Investigator:Marco Antônio Portugal Luttembarck Batalha
Grantee:Eduardo Luís Hettwer Giehl
Supervisor abroad: Holger Kreft
Home Institution: Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
Local de pesquisa : Göttingen University, Germany  
Associated to the scholarship:10/20035-5 - Niche shifts among woody formations in Eastern South America, BP.PD


Correlative studies in ecology are generally inconclusive because several processes may result in similar ecological and evolutionary patterns. For instance, dispersal limitation and niche conservatism can lead to an increased phylogenetic similarity in close locations either because species that evolve in a region are unable to disperse, or because evolving species retain their ancestral ecological niches, thus being unable to colonize different environmental conditions. Alternatively, the importance of these processes may be evaluated by simulation experiments, hereafter process-based models. In this study, we will evaluate three process-based models, aiming to weigh the importance of dispersal limitation and niche conservatism to explain current observed tree species richness within South America. Species richness will be obtained by describing species distributions and by calculating the intersection of distribution boundaries with a grid placed over the region. Dispersal limitation and niche conservatism will be modeled in a spatially explicit framework, with different parameters aiming to mimic the effects of these processes over ecological patterns. In the dispersal limitation scenario, colonization of grid cells will follow a random Poisson dispersion parameter, and therefore, lead to prevailing colonization of grid cells close to sources. In the niche conservatism scenario, species will be able to fulfill the environmental space according to a niche breadth parameter, which will be inherited with subtle random shifts by descendant species. New species will evolve by fragmentation of populations either by random grid cell extinctions, or by the effects of environmental fluctuations in the dispersal limitation and niche conservatism scenarios, respectively. Finally, we will simulate a model that incorporates both processes, mainly differing in that a new species will not spread to every suitable grid cell, except when it accomplishes it by random dispersal. Species richness and species range sizes will then be contrasted between simulation outputs and empirical data to evaluate models predictive power and, thus, the likelihood of these distinct processes. (AU)