The global Cenozoic diversification process of tortoises (Testudinidae).

Great environmental changes may affect the survival capability of a variety of organisms. Testudinidae is the most diverse family of terrestrial chelonians within the whole order (Testudines). Interestingly, however, the number of extinct species overcome the extant ones. In order to understand better how the diversification process of this family occurred, this work used the PyRate software, which estimates both the preservation and diversification processes in a continuous time interval. For such, the software used a list of fossil occurrences obtained from the Paleobiology Database whereas the extant species list was obtained from Catalogue of Life. This way, the software was able to infer the probability of the ancestral clade having resulted in these species during its evolutionary history. The analyses generated graphs containing the diversification, extinction and speciation curves and their respective associated 95% credibility intervals. A great rise in the extinction rate was observed starting 6 million years ago. This rise is believed to be related to the drop of atmospheric CO2 all over the globe at the end of the Miocene, about 8-6 million years ago. This event led to a turnover of the vegetation composition on the warmer areas of the planet, with plants that used C3 metabolism giving way to C4 plants. In terms of landscape, grasses and herbal vegetation, such as savannas, started dominating. As for other animal groups, those herbivores with grazing habits were more successful than those used to only browsing or that did not have enough flexibility of choice.

Patterns of vector species richness and species composition as drivers of Chagas disease occurrence in Brazil.

Chagas disease represents one of the major health issue in Latin America. Epidemiological control is focused on disease vectors, so studies on the ecology of triatomine vectors constitute a central strategy. Recently, research at large spatial scale has been produced, and authors commonly rely on the assumption that geographical regions presenting good environmental conditions for most vector species are also those with high risk of infection. In the present work, we provide an explicit evaluation for this assumption. Employing species distribution models and epidemiological data for Chagas disease in Brazilian territory, our results show that species richness is a poor predictor for the observed pattern of Chagas disease occurrence. Species composition proved to be a better predictor. We stress that research on macroecology of infectious diseases should go beyond the analysis of biodiversity patterns and consider human infections as a central part of the focal ecological systems.

An objective view of biological diversity: how history and epistemology shaped current treatment.

The concept of biological diversity has inspired important discussions throughout the history of ecology. Although its meaning and usefulness have been questioned, it is currently one of the key artifacts of ecology. One way to try to understand why such a concept has undergone so many discussions is to examine its emergence and history from the epistemology perspective. In the present work, we investigated how the emergence of mechanical objectivity (as an epistemic virtue) and trained judgment affected how ecologists address the concept of biological diversity. Thus, we employed the theoretical framework of objectivity (provided by Daston and Galison in Objectivity. Zone Books, New York, 2007) to analyze different periods of scientific literature in ecology ("initial period": end of the nineteenth century and beginning of the twentieth century; "intermediate period": mid-twentieth century; "contemporary period": from the second half of the 1980s). Our results showed that the emergence of mechanical objectivity and trained judgment affected biological diversity research. In particular, the ideal of objectivity behind the way in which the concept of biological diversity is addressed in different fields of contemporary ecology could not be the same.

Multiple dimensions of biodiversity and ecosystem processes: Exploring the joint influence of intraspecific, specific and interspecific diversity.

The positive influence of biodiversity on ecosystem processes was the focus of intense debate in ecology throughout the recent decades, becoming accepted and treated as a new paradigm in contemporary ecology. However, the available literature in this research field extensively explores species richness as an unidimensional measure for biodiversity. The present study explores how different components of biological diversity (number of genotypes, species, and functional groups) can influence an ecosystem process (biomass fixation). A mathematical model was employed and the simulation results showed that species richness per se does not affect the ecosystem productivity. Genotypic richness affected positively the ecosystem, but only if the genotypes are functionally complementary. The functional groups richness always affected positively the simulated ecosystem process. When together, richness at the different components of biological diversity showed stronger effect on ecosystem, and the scenarios with high species, genotypes and functional groups richness were the most productive ones. The results also allowed to observe that the ecosystems which are diverse in terms of functional groups and genotypes can be less susceptible to species loss. Finally, it is argued that a multiple dimension approach to biodiversity is relevant to advance the current knowledge on the relation between biodiversity and ecosystem functioning.

The impacts of population subdivision on the viability of Brachyteles hypoxanthus.

Habitat loss and fragmentation turn continuous large populations into metapopulations of smaller populations, more prone to the negative effects of stochastic processes. We modeled scenarios simulating the subdivision of Brachyteles hypoxanthus populations under different dispersal rates. Results show the existence of a population subdivision threshold, below which subdivision causes the metapopulation structure to collapse. Management should target first the increase in local populations through habitat restoration/protection, and only after populations are sufficiently large, connectivity strategies should take place.