Defaunation in assemblages of medium and large mammals in the Anthropocene and the erosion of its traits: a quantitative analysis for Brazilian biomes

Abstract

Mammals are part of the megafauna and play an important ecosystem role. Over the past 500 years, the assemblages of these animals have been reduced on a large scale in the Neotropics. Anthropic actions are among the main causes of threat and occur in the form of deforestation and fragmentation of ecosystems, which leads to the emptying of mammal assemblages in the tropical forests and savannas of the new world. This loss of mammals can affect evolutionary processes - morphology and behavior - leading to changes in the distribution of traits, which are the characteristics of species that influence the functioning of ecosystems. Working ecosystems usually promote services that meet human needs such as: food, water, fuels, nutrient cycling, primary production, climate regulation, disease, and educational and recreational services. As an example of the impact of traits on the ecosystem and ecosystem services, we have the frugivorous diet. Frugivory contributes to the maintenance of the phytogeographic dynamics of forest remnants, which act in the sequestration and stock of atmospheric carbon, being therefore important in regulating the climate and has an impact on agriculture. Thus, our work aims to understand how the defaunation in mammal assemblages that occurred in the last 500 years in Brazilian biomes affects the distribution of the hypervolume of the traits of the cranial dimensions related to the diet and of the traits of the diet spectrum. Assemblages can be measured by the hyperdimensional space of the traits, and it is expected that integral assemblages have a higher morphological ecologic volume than defaunted assemblages do. The data will be analyzed by Principal Component Analysis (PCA) followed by an analysis by Convex Hull, which will assess the loss of volume (morphological and dietary) between historical and modern value. To test the difference between modern (defaunate) and historical (non-defaunate) eco-morphometric values, the scores of the ordering sites (PCAs) will be obtained and a paired central trend measurement comparison test (eg Student t test) will be applied between modern scores vs. historical ones. By comparing these values, we can understand how defaunition erodes two metrics that imply the functioning of ecosystems. For example, the expected reduction in the hypervolume of the cranial dimensions of the assemblages implies the size of prey consumed or of scattered seeds. The feasibility of the project rests on its low cost since the data will be obtained mainly through inventories available in the literature. Still, we see in this project a great potential for publication in an indexed magazine and in the generation of data for the proponent's course completion work.