Estratégias de defesa contra a megafauna extinta em fitofisionomias do Cerrado brasileiro

Abstract

This study investigates the influence of the extinct South American megafauna on plant anti- herbivory defenses across different vegetation types of the Cerrado biome. We hypothesized that the nature and prevalence of defensive strategies are determined by the interaction between resource availability, particularly soil fertility, and historical herbivory pressures exerted by megafauna. To test this, we compiled functional trait data for woody species of the South American tropical flora from published literature, including leaf size, wood density, specific leaf area, leaf nitrogen, spinescence, and latescence. These data were combined with indicator species lists for savanna, dystrophic “cerradão” forest, mesotrophic “cerradão” forest, deciduous forest, semideciduous forest, and evergreen forest, and analyzed in relation to environmental conditions. Statistical analyses included Principal Component Analysis (PCA) of environmental variables across vegetation types and Bayesian hierarchical regression models for plant defensive traits. Our results show that Cerrado plant defenses arise from the interaction between current environmental conditions and the evolutionary legacy of herbivory. In fertile soils, such as those of deciduous forests, physical defenses predominate, characterized by reduced leaves and high spine density, protecting nutrient-rich tissues from large herbivores. In savannas, low leaf nutritional quality functions as the main defense mechanism, without reliance on small leaves or high spinescence. Dystrophic “cerradão” forest exhibited increased latex production and dense leaves, indicating chemical and structural defenses against smaller herbivores. These findings confirm that plant defenses in the Cerrado are heterogeneous and shaped by its mosaic of vegetation types: fertile environments favor physical defenses protecting nutritious leaves, whereas nutrient-poor environments promote chemical and structural strategies adapted to herbivory by smaller fauna. Overall, this study highlights the combined role of historical and contemporary factors in shaping plant defensive traits in the Cerrado.