Ecological and evolutionary drivers of group living and brain evolution in Caribbean gobies

The complexity of human social life is the focus of social scientists. Similarly, biologists are puzzled by the great diversity of social organization found in animals. Their challenge is to identify the commonalities in the social life of different species, even when comparing very different groups like vertebrates and invertebrates. In this context, a new framework for a common, trait-based approach towards a social synthesis has been proposed. The framework highlights that we need to assemble information about species life history traits (like longevity, fecundity, dispersal patterns, and body size) as well as characteristics of group social organization (such as genetic relatedness, breeding structure and sex ratio) for a comprehensive synthesis aimed at explaining the main drivers of the evolution of social systems. Such detailed information may also help us to understand how social behavior relates to other traits, like brain structure. The hypothesis that complex social life is the main driver for the evolution of enlarged brains and advanced cognition is well established but still difficult to evaluate without detailed knowledge about the traits that capture the life history of each species. For example, brain size can be positively correlated with longevity and negatively correlated with fecundity in many species and although this is relatively well known, this information is rarely integrated into cross-taxa comparative studies of brain structure. Therefore, we need a larger number of trait-based comparative studies on a high diversity of taxonomic clades, bringing together information on both vertebrate (mammals, birds, fishes) and invertebrate (insects, shrimps, spiders) groups with variation in social organization. Fishes are a particularly interesting group for such a comparative approach because they show a great diversity of social organizations and the brain areas linked to social behavior in fishes are present in mammals, birds, reptiles, and amphibians. During my Ph.D., I studied how social behavior linked to brain anatomy in the Caribbean cleaning goby species Elacatinus prochilos. For the current project, I will extend this knowledge to other Elacatinus species, and include valuable information on life history and group organization traits. First, I will review the life history traits available in the literature for as many Elacatinus species as possible (there are in total 31 species). Second, I will conduct field observations in several reefs to quantify key ecological variables (like habitat availability, population density and predation pressure) and describe the group social organization in a few species that encompasses the forms of sociality found in the Elacatinus genus. Finally, I will investigate how all this data link to variation in brain structure. Taken together, detailed information on ecological factors, life history traits, brain structure, and group social organization will allow me to analyze how ecological and evolutionary drivers relate to group living and brain evolution in the Caribbean gobies. Furthermore, by applying the trait-based comparative framework to marine gobies and comparing how group living in marine gobies compares to other fish clades living in completely different environments (like cichlids) or taxonomically distant groups living in similar environments (like marine snapping shrimps) we will gain unprecedented insights into the evolution of sociality in animals.