Sociality in lizards

The reproductive biology of fish exemplifies the competition between conspecifics for the production of offspring (Taborsky 1994, 1997, 2008). This concerns intrasexual conflict, particularly in the male sex, but also the effects of the conflict of interest between the sexes (Henson & Warner, 1997; Maan & Taborsky, 2008; Taborsky & Neat, 2010). Nevertheless, there are remarkable examples of cooperation in fish reproduction, including some of the most highly advanced social systems and levels of cooperation known among vertebrates (Taborsky, 1987, 1994, 2016; Balshine & Buston, 2008). What at first glance may seem contradictory actually reflects alternative solutions to the same problem: individuals competing for resources such as food, shelter, or mates may succeed either through greater resource holding potential or by collaborating with (some of) their competitors. Resource competition may select either for high competence in conflict strategies (e.g. involving aggression or surreptitious exploitation) or for advanced social competence, group formation, and cooperation. Here we discuss which intrinsic characteristics of a taxon and which ecological conditions generate cooperation rather than conflict. Our emphasis will be on reproductive systems because social complexity is typically much greater in the context of reproduction than in other functional circumstances such as food acquisition or predator avoidance (Wilson, 1975; Trivers, 1985). In aquatic animals, the preconditions for advanced levels of sociality differ systematically between freshwater and marine environments, primarily due to the different mechanisms of dispersal. This has strong effects on the evolution of brood care and on the relatedness among conspecifics. Both factors are primary drivers of sociality; hence, the types of social systems that we find in freshwater and marine environments diverge substantially. Therefore, we shall deal with freshwater and marine systems separately where this seems appropriate, but we shall point out commonalities between freshwater and marine fishes wherever possible. Social Diversity How Common is Sociality in Fishes? Even if social complexity is generally highest in the reproductive context, collective and cooperative behavior can also be observed in fish schools and shoals (i.e. a social group staying connected for some time; the term “school” refers to a shoal that shows coordinated movement regarding direction, swimming speed, and distance between its members). These more or less organized conspecific aggregations (Pitcher & Parrish, 1993; Delcourt & Poncin, 2012) are widely viewed as the most characteristic social organization of fish.