Phenomenon of reproductive plasticity in ants

Abstract

Ant colonies are organized in castes with distinct behaviors that together allow the colony to strive. Reproduction relies on one or a few queens that stay in the nest producing eggs, while females of the worker caste do not reproduce and instead engage in colony maintenance and brood caretaking. Yet, in spite of this clear separation of functions, workers can become reproductive under defined circumstances. Here, we review the context in which workers become reproductive, exhibiting asexual or sexual reproduction depending on the species. Remarkably, the activation of reproduction in these workers can be quite stable, with changes that include behavior and a dramatic extension of lifespan. We compare these changes between species that do or do not have a queen caste. We discuss how the mechanisms underlying reproductive plasticity include changes in hormonal functions and in epigenetic configurations. Further studies are warranted to elucidate not only how reproductive functions have been gradually restricted to the queen caste during evolution but also how reproductive plasticity remains possible in workers of some species.

Figure 1. Reproductive plasticity of worker ants.

Workers are not normally involved in reproduction. The presence of a queen (or a dominant reproductive worker, or the presence of brood in species without a queen caste) restricts workers reproduction. In the absence of the queen, workers are able to activate their ovaries and produce progeny. The extent of worker reproduction differs between species. In some species worker reproduction is transient while in others, reproduction can become stable with an extended lifespan.