Behavioural syndromes and their fitness consequences in a socially polymorphic spider, Anelosimus studiosus

The temperate comb-footed spider, Anelosimus studiosus, shows a social behaviour polymorphism: individuals may defend asocial nests against intrusion by conspecifics or cooperate with them in multifemale nests. A suite of behavioural traits, including response to predators and prey, degree of superfluous killing, exploratory behaviour and general level of activity, was examined in laboratory trials to: (1) establish the extent to which these traits are correlated with social phenotype and (2) explore the potential adaptive value of this trait suite to the respective asocial and social phenotypes. Populations from the two latitudes studied, 26° and 36°, showed similar suites of correlated traits or syndromes. The individuals tested generally fell into two groups in the behavioural trials, although the asocial individuals from the mixed-phenotype population at 36° latitude were intermediate with respect to some of the measures. Individuals scored as ‘social’ generally showed less aggressive behaviour towards predatory cues, were less responsive to prey encountering their webs, showed little evidence of superfluous killing of prey and showed lower levels of activity than did most individuals scored as ‘asocial’. These results suggest linkage or pleiotropy between social behaviour and these traits. The behaviour of individuals in staged, mixed-phenotype feeding pairs indicated that social individuals may suffer fitness consequences in polymorphic populations. These results are discussed with respect to the stability and dynamics of the respective phenotypes in polymorphic populations.