Heatwole, S. J. | Search bioRxiv

bioRxiv2023

Multi-level framework to assess social variation in response to ecological and social factors: modeled with coral gobies

1.Understanding variation in social organization that does not have a strong phylogenetic signal represents a key focus of research in behavioural and evolutionary ecology. In light of this, we established a sociality framework that identifies four categories of variation in social organisation that range from large-scale to fine-scale and can each be related to various ecological factors: (1) forms of sociality, (2) degree of sociality, (3) social plasticity, and (4) within-group plasticity. We modelled this framework by quantifying the four categories of variation over time, space and disturbance regime using multiple species of coral-dwelling gobies from the genus Gobiodon. Gobies are a particularly interesting model system as they vary in social structure, have within-group cooperation and form mutualistic relationships with their coral hosts which are vulnerable to climatic disturbances. We found that gobies varied in forms of sociality - from being solitary, to paired or group-living depending on location and disturbance regime. Only low or moderate degrees of sociality were observed in gobies, and this was influenced by location or disturbance regime depending on species. Gobies were more often solitary or pair-forming than group-forming (which became extremely rare) in a high disturbance regime whereas they were more often found in groups in a moderate disturbance regime. The size of coral hosts affected the social plasticity of gobies, and corals were smaller due to climatic disturbances. Gobies did not exhibit within-group social plasticity, as there were no changes to the structure of size-based hierarchies or sex allocation patterns with location or disturbance regime. Lastly, by combining the four categories of variation, we find that there is a high loss of sociality in coral-dwelling gobies due environmental disturbances, which likely affects overall goby survival as living in groups can improve survival and fitness. By using our structured framework, we identified which categories of social variation were influenced by ecological factors like location and disturbance. This framework therefore provides an excellent tool for predicting future responses of animal societies to environmental stressors.

ecology↗

bioRxiv2021

Habitat size, health and saturation do not alter movement decisions or the preference for familiarity in a social coral-reef fish

While habitat is often a limiting resource for group-living animals, we have yet to understand what aspects of habitat are particularly important for the maintenance of sociality. As anthropogenic disturbances rapidly degrade the quality of many habitats, site-attached animals are facing additional stressors that may alter the trade-offs of moving or remaining philopatric. Here we examined how habitat health, size and saturation affect movement decisions of a coral-dwelling goby, Gobiodon quinquestrigatus, that resides within bleaching-susceptible Acropora coral hosts. To assess effects of habitat health, we translocated individuals far from their home corals into dead corals with the choice of adjacent healthy corals. To assess effects of habitat size and saturation, we manipulated coral sizes and the number of residents in healthy corals. Remarkably, 55% of gobies returned home regardless of treatment, 7% stayed in the new coral, and the rest were not found. Contrary to expectations, habitat factors did not affect how costs of movement influence group-living decisions in this species. These site-attached fishes preferred to home instead of choosing alternative habitat, which suggests a surprising awareness of their ecological surroundings. However, disregarding alternative high-quality habitat is concerning as it may affect population persistence under conditions of rapid habitat degradation.

animal behavior and cognition↗