Evolution of eusociality and the soldier caste in termites: Influence of intraspecific competition and accelerated inheritance

Abstract

We present new hypotheses and report experimental evidence for powerful selective forces impelling the evolution of both eusociality and the soldier caste in termites. Termite ancestors likely had a nesting and developmental life history similar to that of the living family Termopsidae, in which foraging does not occur outside the host wood, and nonsoldier helpers retain lifelong options for differentiation into reproductives. A local neighborhood of families that live exclusively within a limited resource results in interactions between conspecific colonies, high mortality of founding reproductives, and opportunities for accelerated inheritance of the nest and population by offspring that differentiate into nondispersing neotenic reproductives. In addition, fertile reproductive soldiers, a type of neotenic previously considered rare and docile, frequently develop in this intraspecific competitive context. They can be highly aggressive in subsequent interactions, supporting the hypothesis that intercolonial battles influenced the evolution of modern sterile termite soldier weaponry and behaviors.

Eusociality: Origin and consequences

“…Group selection which with the addition of cooperative behavior becomes colony selection, is the result of the interaction of entire groups with their environments (6,(7)(8)(9)(10)(11), conditioned by the efficiency of their internal opera-tions (12). It promotes harmony among group members and genetic fitness of the group as a whole, once colony level is attained, and its effect is thereby inherently binding.…”

Reproductive skew drives patterns of sexual dimorphism in sponge-dwelling snapping shrimps

“…As most males are reproductively capable but the queen typically mates with a single one [55], competition among males and the variance of male reproductive success may remain high in eusocial Synalpheus species. Although it is unclear how often a worker could inherit a colony in eusocial shrimps, worker inheritance occurs in eusocial species like termites [18,54,56] and naked mole-rats [57]. Although species with multiple breeding females per colony (e.g.…”

Growing out of a caste - reproduction and the making of the queen mole-rat

“…When the queen dies or is removed from the colony, subordinate females can undergo rapid sexual maturation, and a violent competition often ensues until a victor emerges to become the new queen (Clarke and Faulkes, 1997). Mole-rats thus share a remarkable number of features in common with eusocial insects and these findings have generated considerable interest in both the evolutionary pressures resulting in eusociality and the mechanisms that allow different castes to develop in such disparate species (Thorne, 1997;Thorne et al, 2003).…”