, 1997; Fewell & Page Jr, 1999; Parrish, Viscido & Grünbaum, 2002; Theraulaz et al., 2003; Couzin, 2008). Importantly, emergence mechanisms require

only spatial proximity among individuals, leading to novel behaviors and patterns without underlying genetic changes in behavioral strategy as individuals interact with one another and their shared environment. If the defining features of eusociality are similarly self-organizing in nature, this would provide a mechanism for their appearance in a single step at the origin of group formation. Critically evaluating these alternative trajectories of social evolution is not straightforward, as the initial characteristics of extant social species, whether emergent or not, are likely to have long since been superseded by secondary adaptations

to social life. One approach to recovering what incipient groups may Selleckchem SB525334 have been like is to assemble artificial social groups in species that are normally solitary, but tolerant enough of conspecifics to persist in groups without fatal aggression and group dissolution. Because such individuals have no evolutionary history of social cooperation, their behaviors under experimental group formation should be a function of their intrinsic behavioral repertoires and any emergent properties resulting from interactions with the shared physical environment and/or other group members. As predicted by the emergent property hypothesis, artificially assembled groups Dabrafenib molecular weight of insects that are normally solitary during the life stage being investigated

show pronounced division of labor in nonreproductive tasks such as nest construction and defense, suggesting that these can emerge from self-organizing processes (Fewell & Page Jr, 1999; Helms Cahan & Fewell, 2004; Jeanson, Kukuk & Fewell, 2005; Jeanson & Fewell, 2008; Holbrook et al., selleck chemicals llc 2009). However, whether self-organization can also cause the emergence of division of labor in reproduction has scarcely been investigated, despite its centrality to the origin and elaboration of eusociality (Sakagami & Maeta, 1987). This has led authors to question whether emergent property scenarios have any applicability to the evolution of eusociality (Bourke, 2011; Duarte et al., 2011; Herre & Wcislo, 2011). In this study, we experimentally test whether self-organizing mechanisms can spontaneously generate reproductive division of labor by creating forced associations of colony-founding queens of the harvester ant species Pogonomyrmex barbatus. Although ants show highly derived eusocial structure during most of the life cycle, queens of many species found colonies alone, excavating the nest and rearing the first cohort of workers in complete social isolation. Because queens are strictly solitary during this period, they should be selected for a behavioral repertoire similar to that of a hypothetical solitary ground-nesting ant ancestor.