Ecological constraints and benefits of philopatry promote group-living in a social but non-cooperatively breeding fish

Abstract

Why non-breeding subordinates of many animal societies tolerate group-living remains a pertinent question in evolutionary biology. The ecological constraints and benefits of philopatry hypotheses have the potential to explain the maintenance of group-living by specifying the ecological conditions favouring delayed dispersal over independent breeding by subordinates. In this study, I used field and laboratory experiments to investigate the role of ecological and social factors on the dispersal decisions of nonbreeding subordinates in the coral-dwelling fish, Paragobiodon xanthosomus (Gobiidae). Subordinate dispersal was strongly influenced by ecological constraints (habitat saturation and risks of movement) and benefits of philopatry (relative coral size). Social factors, namely social rank and forcible eviction, did not affect the occurrence of subordinate dispersal. These results suggest that selection has favoured subordinate P. xanthosomus, which employ a mixed strategy-switching tactics in response to three ecological factors-despite having low mobility and extreme habitat-specific requirements. Furthermore, this study demonstrates the generality of the ecological constraints and benefits of philopatry hypotheses as explanations for group-living in species where subordinates are unrelated to breeders, provide no help and do not strictly delay dispersal.

Better off alone! Reproductive competition and ecological constraints determine sociality in the African striped mouse (Rhabdomys pumilio)

“…Previous experiments performed during the breeding season in fish (Bergmüller, Heg & Taborsky 2005; Stiver et al. 2006; Wong 2010), birds (Pruett‐Jones & Lewis 1990; Walters 1991; Komdeur 1992) and mammals (Jacquot & Solomon 2004) already confirmed predictions of the ecological constraints hypothesis especially that groups form when resources are limited (Koenig et al. 1992; Kokko & Ekman 2002; Baglione et al.…”

The Right Tools for the Job: Cooperative Breeding Theory and an Evaluation of the Methodological Approaches to Understanding the Evolution and Maintenance of Sociality

“…While cooperative rearing of young has not been observed in marine fish, there are group living species which are typically comprised of unrelated individuals and often a monogamous breeding pair with a number of non-breeding subordinates (Taborsky and Wong, 2017). These groups bear many resemblances to cooperative breeding birds and mammals and cooperative breeding theories have proven successful in explaining the evolution and maintenance of these social systems (Buston and Balshine, 2007;Wong, 2010;Wong and Buston, 2013). Unconventional life-history strategies, such as bi-directional sex-change, and amenability to experimental manipulation and observation present further opportunities to challenge hypotheses of social evolution under novel conditions.…”

“…While such contrasts enable broad generalizations to be made, they fall short of identifying causality of effects. In contrast to this methodology, studies that have tested these hypotheses through refined experimental manipulation of characteristics associated with the evolution of sociality (Komdeur, 1992;Baglione et al, 2002;Wong, 2010) do demonstrate causality, but their necessary focus on just one or a few species greatly reduces the ability to draw general conclusions. Therefore, it is through using a combination of these approaches for a given lineage that holds the potential to provide an insight into the generality and causality of sociality across a broad range of species (Figures 1, 2).…”

“…Offspring of such groups often, but not always remain on the natal territory and many groups are therefore comprised of subordinates related to the dominant breeders, in which case relatedness is high (in Hamilton's rule) and the likelihood of cooperative actions being selectively favored is raised (Bourke, 2014). However, a growing number of studies have revealed social systems where non-breeding subordinates disperse to other groups and are unrelated to the dominant breeders (Double and Cockburn, 2003;Gardner et al, 2003;Awata et al, 2005;Dierkes et al, 2005;Wong, 2010;Riehl, 2013). In these cases, cooperative rearing of young may still take place as well as other forms of cooperative behavior in order to avoid conflict and maintain a stable group structure (Gardner et al, 2003;Wong et al, 2007).…”

“…Because of the logistical constraints of manipulative experiments, many studies have focused on smaller species which are more easily housed or species with habitats that can be easily manipulated in situ. Social marine or freshwater fish make excellent study species for this methodology as they tend to congregate on discrete habitat patches which can be easily picked up and moved or simulated in aquaria, making experimental manipulations of ecological factors highly feasible (Wong, 2010). Many are also demersal spawners which provides a convenient measure of reproductive success and fecundity (Buston, 2004a; FIGURE 3 | Approximate number of publications on cooperative breeding for each methodology.…”