Behavioral diversity (ethodiversity): A neglected level in the study of biodiversity

Abstract

The concept of biodiversity embraces a multifaceted and hierarchical analysis of the complexity of life, with implications in many areas of science, philosophy, ethics, politics, and even religion. Three levels are included in the commonly accepted definitions: genetical, species, and ecosystem diversity, going from the intraspecific level to the landscape. Here, I argue that a fourth level, never included in biodiversity studies, is of prominent relevance: ethological diversity or "ethodiversity." There is a growing number of studies describing alternative behaviors, behavioral plasticity, learning, and even personality, as characteristics of animal populations or individuals. Ethodiversity is also relevant in unraveling cryptic biodiversity, such as species that differ in their behavior but are otherwise undistinguishable. Maintaining ethodiversity is therefore essential in conservation, and cannot be achieved simply by focusing on genetic diversity. Behavior has profound ecological consequences, particularly in species interactions, and is a crucial element in the adaptability of animals to new environments. Ethodiversity is important at the intraspecific, inter-population, and species level and has practical relevance in several fields, like captive breeding, eco-novelty, and popular science. Finally, I expect ethodiversity to show a latitudinal cline, with more diverse and elaborate behaviors per species in the tropical regions, given the increase in interactions near the equator.