Biodiversity has gone through different configurations throughout the history of life. Changes in biodiversity in deep time (millions of years) have been caused either by abrupt or gradual environmental changes, determined simultaneously by biotic and abiotic factors. These dynamics can be studied using historical approaches that use either the fossil record or molecular phylogenies. The development of complex models that estimate speciation and extinction rates has allowed the study of a great share of our biota. However, macroevolutionary studies at global scales are relatively rare, especially those that seek to infer eco-evolutionary mechanisms behind biodiversity changes. This is due in part to the difficulty of identifying and isolating the relevant environmental factors, and to the difficult of identifying the relevant selective pressures. Determining what constitutes specie's "environment" is not an easy task. One way to represent the "whole environment" of a species is the biome where it belongs. Biomes represent particular combinations of abiotic (e.g. temperature, moisture) and biotic (e.g. ecological interactions) variables, whose areas have varied considerably over the past 50 million years. In order to understand how gradual environmental changes might have influenced diversification dynamics, we will investigate how changes in biome total area might have affected the rates of speciation and extinction, as well as eco-space occupation of Bird and Mammal lineages in different biomes of our planet. To achieve this goal, we will use molecular phylogenies, distribution maps, ecology data (body size and diet) of Birds and Mammals species, the phylogenetic comparative method, and analytical models. We expect that lineages associated with biomes which have experienced a decrease in total area over the last 50 million years (e.g. tropical rainforests) should exhibit negative diversification rates, that is, extinction rates higher than speciation rates, whereas lineages associated with biomes which have experienced an increase in total area (e.g. tropical savannas) should exhibit a positive diversification.. In addition, we propose that eco-space occupation should be more densely occupied in lineages inhabiting contracting biomes, and that rates of phenotypic evolution of those lineages should be higher, because a decrease in resource availability might lead to stronger interspecific competition.
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