Division of labor and the evolution of task sharing in queen associations of the harvester ant Pogonomyrmex californicus

Abstract

Division of labor is a key factor in the ecological success of social groups. Recent work suggests that division of labor can emerge even without specific adaptations for task specialization and that it can appear in incipient social groups as a self-organizational property. We investigated experimentally how selection and self-organization may interact during the evolution of division of labor by examining task performance in groups of normally solitary versus normally social ant queens. We created social pairs of colony-founding queens from two populations of the ant Pogonomyrmex californicus, one in which queens are normally solitary and one in which queens form foundress groups, and observed their behavior during nest excavation. In both populations, one of the two queens usually performed most of the excavation, becoming the excavation specialist. We could predict which queen would become the specialist based on their relative propensities to perform the task in other contexts, consistent with a variancebased model of task specialization. The occurrence of specialization even when group members were not adapted to social life suggests that division of labor may well have been present in incipient queen groups. However, division of labor can result in cost skew among group members, and thus, paradoxically, within-group selection may constrain or even reduce specialization. Consistent with this effect, pairs of normally solitary queens were significantly more asymmetrical in their task performance than normally social pairs, in which both queens nearly always performed the behavior to some degree.

Nesting habitat segregation between closely related terricolous sphecid species (Hymenoptera:Spheciformes): key role of soil physical characteristics

“…Such behavior has been documented in Mellinus arvensis (Ghazoul 2001), Cerceris antipodes (Alcock 1980;McCorquodale 1989), Cerceris australis (Evans and Hook 1982), Cerceris cribrosa (Elliott and Elliott 1987), Cerceris simplex (Alcock 1975), and Andrena erythronii (Michener and Rettenmeyer 1956). Nesting in highly compact substrates may also lead to the decreased fitness of digging individuals, as in fossorial ant communities, since the increased energy expenditure and desiccation due to cuticular abrasion is thought to be related to higher mortality rates of adult excavation specialists compared to the non-specialists (Fewell and Page 1999;Johnson 2000;Helms Cahan andFewell 2004, but cf. Holbrook et al 2009).…”

The emergence of reproductive division of labor in forced queen groups of the ant Pogonomyrmex barbatus

“…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 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, ; Helms Cahan & Fewell, ; Jeanson, Kukuk & Fewell, ; Jeanson & Fewell, ; Holbrook et al ., ). 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, ).…”

Emergence and Consequences of Division of Labor in Associations of Normally Solitary Sweat Bees

“…2004). However, they can also be applied to simpler, non‐eusocial groups, and the same mechanisms could lead to the emergence of basic forms of division of labor early in social evolution (Page 1997; Fewell & Page 1999; Costa & Ross 2003; Helms Cahan & Fewell 2004; Jeanson et al. 2005, 2008; Jeanson & Fewell 2008).…”

“…Task specialization and division of labor have been observed in forced associations of normally solitary animals, including Ceratina carpenter bees (Sakagami & Maeta 1987), Lasioglossum sweat bees (Jeanson et al. 2005, 2008), and Pogonomyrmex seed‐harvester ant queens that typically initiate colonies alone (Fewell & Page 1999; Helms Cahan & Fewell 2004; Jeanson & Fewell 2008). Evidence suggests that behavioral differentiation in these incipient groups can be achieved through a combination of response threshold variation and spatial dynamics (Fewell & Page 1999; Helms Cahan & Fewell 2004; Jeanson et al.…”

“…2005, 2008), and Pogonomyrmex seed‐harvester ant queens that typically initiate colonies alone (Fewell & Page 1999; Helms Cahan & Fewell 2004; Jeanson & Fewell 2008). Evidence suggests that behavioral differentiation in these incipient groups can be achieved through a combination of response threshold variation and spatial dynamics (Fewell & Page 1999; Helms Cahan & Fewell 2004; Jeanson et al. 2005).…”