Integrating ecological and evolutionary processes in stochastic biogeographical models

Date of Completion

January 2010


Biology, Ecology|Biology, Evolution and Development|Biology, Histology




The most conspicuous pattern in biogeogeraphy is the increase in number of species (species richness) from the temperate zone (higher latitudes) to the tropics (lower latitudes). Understanding processes that create and maintain biodiversity is a key factor for defining strategies for conservation efforts. Evolutionary processes underlying spatial patterns in species richness remain largely unexplored, and correlative studies lack the theoretical basis to explain these patterns in evolutionary terms. I developed a series of spatially explicit simulation models to evaluate, under a pattern-oriented modeling approach, the roles of centers of origin, dispersal capacity, environmental fluctuations and evolutionary niche dynamics (the balance between niche conservatism and niche evolution processes) in the creation and maintenance of patterns of species richness. Chapter 1 consists of one of the first attempts to link ecological and evolutionary processes in a single model framework. I model the size, shape, and location of species' geographical ranges in a multivariate heterogeneous environmental landscape by simulating an evolutionary process in which environmental fluctuations create geographic range fragmentation, which, in turn, regulates speciation and extinction. In Chapter 2, I focus on the potential drivers of the species richness patterns of endemic terrestrial vertebrates in Brazilian Cerrado. My analyses clearly show that geometric constraint on the shape of the biome is the strongest predictor of endemic vertebrate richness in Brazilian Cerrado. There are, however, additional drivers of species richness patterns, such as energy-water balance and spatially biased biodiversity knowledge. Chapter 3 presents SAM (Spatial Analysis in Macroecology, which is a freeware application that offers a comprehensive array of spatial statistical methods that are most commonly used in macroecology and geographical ecology. The simulation model in Chapter 4 is constrained to the reproduce empirical range size distribution for a defined biota. This biogeographical simulation model was designed and implemented to evaluate the effects of center of origin, dispersal capacity, and niche conservatism on spatial patterns of avian species richness in the New World. Results indicate that, in the most explanatory models, parameter values indicate that environmental factors have a strong influence over center of origin, dispersal, and speciation events; dispersal capacity of species is relatively high; and most species have relatively similar association with environmental factors. ^