The role of ecological and social constraints in social evolution of coral reef fishes
Embargo Date
2024-03-29
OA Version
Citation
Abstract
Identifying the factors that promote social evolution, and investigating how they influence the costs and benefits of living in a group, is a major goal of evolutionary biology. My dissertation research generates a novel framework for understanding the effect of alternative options, i.e. outside options (ecological constraints) and inside options (social constraints), in social evolution using two marine systems, the clown anemonefish Amphiprion percula and the humbug damselfish Dascyllus aruanus. In the first part of my dissertation, I explored how ecological and social constraints influence the evolution of non-breeding strategies in A. percula. Using three manipulation experiments in the wild, I explored why clownfish non-breeders engage in peaceful cooperation, waiting to inherit breeding positions, rather than engaging in one of two alternative non-cooperative options: i) the outside option, i.e. leaving to breed elsewhere; and ii) the inside option, i.e. contesting to breed at home. I demonstrated that clownfish non-breeders will disperse, when ecological constraints (risk of mortality during dispersal) are experimentally weakened, and will contest, when social constraints (risk of eviction during contest) are experimentally relaxed. In the second part of my dissertation I broadened our understanding of the effect of alternative options in social evolution using the humbug damselfish D. aruanus, a species with a more complex social system. First, I developed a new tagging technique and examined the survival time of the tags at various positions on the body of the fish. Next, I developed an essential method for data collection and behavioral observations of D. aruanus by i) generating an ethogram describing the behavioral repertoire of the species and ii) investigating how these fish responds to the presence of human observers and how the method of data collection may affect the quality of behavioral data. Subsequently, using a manipulation experiment in the wild, I examined if the intensity of conflict and cooperation vary with respect to the ecological and social context. I characterized habitat surrounding groups and investigated whether social context (i.e. fish size, size ratios, and group size) or ecological context (i.e. focal coral size, neighboring corals size, and number of neighboring groups) influenced the intensity of conflictive and cooperative interactions. Then, I experimentally increased individuals’ outside options by adding a vacant coral and measured the intensity of conflictive and cooperative interactions in the presence and absence of the outside option. I showed that the effect of the experimental manipulation of ecological constraints on conflictive interactions in D. aruanus depends on the current ecological and social context surrounding groups and individuals, while the effect on cooperative interactions depends only on the ecological context. Together, the results of my dissertation research reveal how, in both A. percula and D. aruanus, ecological and social constraints act in concert influencing social dynamics and group stability, providing new insights into social evolution. Doing so highlights the importance of studying the evolution of cooperation and non-breeding behaviors in taxonomically varied social systems, to generate a more broad and solid framework for understanding social evolution.