Selection for Collective Aggressiveness Favors Social Susceptibility in Social Spiders

Abstract

SUMMARY Particularly socially influential individuals are present in many groups [1–8], but it is unclear whether their emergence is determined by their social influence versus the social susceptibility of others [9]. The social spider Stegodyphus dumicola shows regional variation in apparent leader-follower dynamics. We use this variation to evaluate the relative contributions of leader social influence versus follower social susceptibility in driving this social order. Using chimeric colonies that combine potential leaders and followers, we discover that leader-follower dynamics emerge from the site-specific social susceptibility of followers. We further show that the presence of leaders increases colony survival in environments where leader-follower dynamics occur. Thus, leadership is driven by the “social susceptibility” of the population majority, rather than the social influence of key group members.

Collective aggressiveness limits colony persistence in high‐ but not low‐elevation sites at Amazonian social spiders

“…We measured colonies’ aggressiveness by placing dummy prey (1 cm sections of dead leaf) 4 cm from the rim of the nest basket, and vibrating it with a handheld vibratory device until spiders emerged and seized the dummy prey (Pruitt et al., ), between 1000 and 1600 hr. We recorded the latency of the first spider to contact the dummy and the number of spiders moving towards the dummy at this time.…”

“…Social organisms provide an interesting case study for evolutionary ecologists, because trait differences occur at both the individual‐level and between groups, in terms of their collective traits (Bengston & Jandt, ; Jandt et al., ; Wray & Seeley, ). Like individual traits, a growing body of evidence conveys that group traits are often associated with group success (Gordon, ; Shaffer et al., ; Wray, Mattila, & Seeley, ), and that these links can vary between environments (Pruitt & Goodnight, ; Pruitt et al., ). Site‐specific selection may therefore contribute to biodiversity by promoting intraspecific variation and local adaptation in group‐level traits.…”

“…We use this variation in elevation to examine whether the relationship between group behaviour and persistence varies across habitat types and along an elevation gradient. In particular, we hypothesize that collective aggressiveness should be favoured at sites with low prey availability (Pruitt et al., ). For A. eximius , low‐elevation sites are reasoned to be resource and enemy rich because they harbour larger average prey sizes and higher ant densities at our study sites and the surrounding areas (Guevara & Aviles, , ; Powers & Aviles, ).…”

Comparative genomics identifies putative signatures of sociality in spiders

“…The social spider Stegodyphus dumicola is native to central and southern Africa (Johannesen et al 2007) and has been widely used to study the evolutionary ecology of group living (Pruitt et al 2019(Pruitt et al , 2018Berger-Tal et al 2014;Grinsted et al 2013). We collected three colonies of aproximitly 80 individuals each from Kalkrand, Namibia, in February 2017 and housed them in the lab, feeding them with crickets ad libitum until RNA extraction.…”

Potential feedback between coral presence and farmerfish collective behavior promotes coral recovery

“…Several recent studies on 'collective personality' or 'colonylevel personality' have linked variation in group behavior with group growth rates (Pruitt 2012), productivity (Modlmeier et al 2012), and resource allocation strategies (Bengston et al 2017). Some studies have revealed that the relationship between group behavior and success can differ situationally (Pruitt et al 2018a). However, the broader ecological consequences of such between-group variation have not been rigorously evaluated, despite the fact that animal social groups often have large impacts on their environments (Human and Gordon 1996, Goheen and Palmer 2010, Sih et al 2011).…”