Female clustering in cockroach aggregations—A case of social niche construction?

Abstract

Individuals in groups can suffer costs through interactions with adversarial or unknown conspecifics. Social niche construction allows individuals to buffer such potential costs by only engaging in preferred associations. This may be particularly beneficial in insect aggregations, which are often large and highly fluid. However, little is known regarding the structuring of such aggregations. Here we use social network analyses to test for fine‐scale social structure in resting aggregations of the sub‐social cockroach Diploptera punctata and to explore the social pressures that contribute towards such structure. We showed that females were significantly more gregarious than males and formed the core of the proximity network, thus demonstrating a higher level of social integration. This fine‐scale structure is likely to result from females displacing males; females initiated most displacements whilst males received the majority. We explain this behaviour in terms of social niche construction by showing that females received significantly fewer approaches and investigations at more female‐biased local sex ratios. We therefore suggest that female social clustering occurs in this, and presumably other, species to reduce potential costs associated with male harassment. This demonstrates how social niche construction can lead to higher level social structure; we suggest this approach could be used across a range of species in order to improve our understanding of the evolution of sociality.

Juvenile Gouldian Finches (Erythrura gouldiae) form sibling sub-groups during social integration

“…Some have suggested that females prefer to interact with other females to buffer against destabilizing interactions with males. Studies in baboons, horses, and others have shown that the presence of strong stable female relationships are associated with increased survival and fitness (Cameron, Setsaas & Linklater, 2009;Carter, Lee, Marshall, Ticó & Cowlishaw, 2015;Silk, et al 2009Silk, et al , 2010 and studies in the cockroach Diploptera punctata and guppies have suggested that female aggregations limit intrusions by males (Stanley, Liddiard Williams & Preziosi, 2018). If male interactions have a destabilizing effect, we should also observe that they are preferentially avoided.…”

“…Across taxa there has been a tendency for females to form strong connections with other females, whereas males disperse to neighboring groups (Ward & Webster, 2016). In mammals (Stanley, Liddiard Williams, & Preziosi, 2018), birds (Kohn, King, Scherschel, & West, 2011), and insects (Stanley, Williams, Preziosi 2017) females have been observed to form cohesive female subgroups within the larger group. Strong connections among familiar females often have beneficial consequences for females such as reduced risk from male harassment (Cameron, Setsaas & Linklater,.…”

Differential female sociality is linked with the fine-scale structure of sexual interactions in replicate groups of red junglefowl, Gallus gallus

“…Female-female social clustering may therefore reflect an effective strategy to avoid harassment. Similar patterns in cockroaches, D. punctata, have led to the suggestion that females may engineer the sex ratio of their social environment, biasing it towards females to avoid costly male harassment [26]. Similarly, female eastern mosquitofish school closer together in the presence of males, which dilutes male harassment [32,63].…”

“…Moreover, the effect of female competition might be counteracted by the need for females to group together (e.g. to avoid male harassment [26,31,35]). Intersexual associations were closely related to patterns of sexual behaviour.…”

“…Recent work has begun to reveal the importance of female social strategies in mediating the structure of sexual networks. Female sociality may emerge as a response to male sexual behaviour, such as when male harassment disrupts female aggregations and females alter space use, use refuges or modify habitat preferences to avoid males, as has been shown in a range of organisms, including cockroaches, Diploptera punctata [26], water striders, Aquarius remigis [8,23], solitary bees, Anthophora plumipes [27], guppies, Poecilia reticulata [28][29][30], mosquitofish, Gambusia holbrooki [31,32], Columbian ground squirrels, Urocitellus columbianus [33], South American sea lions, Otaria flavescens [34] and Sumatran orangutan, Pongo pygmaeus abelii [35]. Female social strategies may regulate the level of male competition and sexual harassment through behaviours consistent with social niche construction, such as by grouping together, associating with other, relatively more attractive females or with males that provide protection from harassment [26,29,31,[34][35][36].…”