Geographic patterns of biodiversity

 

Life on earth is not distributed homogeneously throughout the globe, with some regions harboring a lot more biodiversity than other regions. Understanding the forces driving such geographical gradients has long been the goal of ecologists and biogeographers alike. We join this long-standing endeavor bringing together macroecological, (macro)evolutionary and statistical approaches to describe, evaluate and ultimately unravel the processes responsible for the geographic biodiversity gradients. Although most of our research concerns broad spatial and temporal scales (relative to the clades under study), we are also interested in smaller-scale patterns such as regional, biome, and landscape scales.

 

Ecogeographical patterns

 

Certain species traits vary geographically responding to different ecological, physiological and evolutionary drivers. Such variations are known as ecogeographical rules (e.g. Bergmann’s rule: an increase in body size towards higher latitudes/altitudes) and not satisfying explanation for their causes has yet been reached. Applying spatial and phylogenetic methods along with distributional, physiological and trait data, we try to explain why ecogeographical rules emerge and contribute to the understanding of their causes.

 

Phylogenetic comparative methods

 

Many ecological studies rely on the comparison between different species’ traits (e.g. body size vs. metabolic rate) and their response to environmental or other factors (e.g. body size vs. temperature). However, the application of conventional statistical tests to analyze such comparisons suffers from a fundamental problem. Species cannot be considered as independent observations owing to their shared ancestry. Thus interspecific comparisons must explicitly consider species evolutionary history. Phylogenetic comparative methods (PCMs) have been developed for such purpose. The application of well-known PCMs as well as the development of new PCMs is a strong component of our research in the lab, which also includes the explicit consideration of phylogenies in order to model evolutionary processes responsible for biodiversity patterns.

 

Geographical genetics

 

Biodiversity has many different features, from genes to ecosystems, which should be considered when trying to understand the causes of biodiversity patterns. Accordingly, our research not only focuses on organismic studies (i.e. focused on species assemblages) but also on lower-level features such as genetic patterns within species and populations. We apply spatial and phylogenetic statistical approaches to understand geographic patterns of genetic properties as well as to identify patterns at this level of organization that can be relevant for the conservation of biodiversity.

 

Spatial statistics

 

Nearly all biodiversity patterns are geographically structured, showing different properties in distinct locations but also similar properties when locations are geographically close. Such spatial autocorrelation – ‘the property of random variables taking values, at pairs of locations a certain distance apart, that are more similar (positive autocorrelation) or less similar (negative autocorrelation) that expected for randomly associated pairs of observations’ (Legendre 1993) – represents a potential statistical problem but also the possibility of recognizing and understanding the causes of spatial structure in biodiversity patterns. Research in the lab relies heavily on spatial statistical techniques and, owing to the lack of integrated softwares for applying such techniques; we also develop theory, methods and computer applications to deal properly with spatially structured biodiversity data.

 

Conservation biogeography

 

Biogeography aims to describe and understand geographic biodiversity patterns. Such pattern description is one of the first steps towards informed conservation actions. We apply biogeographic concepts and tools, as well as different theoretical and methodological frameworks in order to identify conservation priorities. We also recognize and investigate biodiversity patterns at different spatial and temporal scales (local to continental and microevolutionary to macroevolutionary) with the goal of understanding their causes and contributing to the development of conservation assessments and efficient conservation planning.

 

Paleobiology

 

Biodiversity patterns are present at both spatial and temporal scales. However, the simultaneous consideration of both spatial and temporal views of biodiversity has not been fully accomplished owing to the independent research traditions of paleontology and macroecology. We advocate an integrated view of biodiversity patterns in which macroecology explicitly incorporates evolutionary dynamics through the consideration of fossil data and phylogenies. Accordingly, we also include in our research lines evolutionary approaches that explicitly deal with extant (“phylogenetic macroecology”) and extinct species (“paleo-macroecology”).