Alternative reproductive tactics in females: the case of size polymorphism in winged ant queens

Abstract

Alternative reproductive tactics are common in males but rather rare in females. In this respect, ants are apparently an interesting exception. Ant queens can either start a new colony on their own or utilize the work force of existing colonies for dependent colony founding. As the success of these different options depends on body reserves of the queens, the finding of two different classes of alate queens in some ant species that differ only in size strongly suggests alternative modes of reproduction. Studies of queen size polymorphism from a number of ant species differ in scope and also in their results. Nevertheless, across taxa evidence exists that small queens found dependently while their larger conspecifics found colonies on their own. However, in most cases it is not clear whether the small queens exploit unrelated colonies (intraspecific "social parasitism") or return to their natal colonies. In some ant species the queen size polymorphism might constitute an evolutionary transition to either interspecific social parasitism or a morphologically more pronounced queen polymorphism linked to dispersal. In others, queen size polymorphism might be a stable phenomenon. Although it is important in this context whether queen size polymorphism is caused by a genetic polymorphism or phenotypic plasticity, so far no conclusive evidence about proximate mechanisms of size determination has been presented. Some considerations are made about the question why female alternative reproductive tactics correlated with morphological adaptations are comparatively widespread in ants.

Alternative life-histories in a socially polymorphic ant

“…This difference supports the hypothesis that queens from single-queen colonies disperse and found new colonies independently, and thus need large energy reserves, whereas queens from multiple-queen colonies stay in their natal nest and disperse with workers. Such morphological differences are well documented both across and within species (Keller and Passera 1989;Rü ppell and Heinze 1999). Hence, the observed queen polymorphism suggests that F. selysi queens originating from different colony types differ in dispersal and mode of colony founding.…”

Multiple Cases of Striking Genetic Similarity Between Alternate Electric Fish Signal Morphs in Sympatry

“…Congruent with our genetic results, an apparent lack of appreciable microhabitat partitioning is consistent with the presence of persistent EOD dimorphisms in each of several panmictic gene pools. A strict association between signal types and alternative mating tactics would appear unlikely since these kinds of tactics are almost always sex-limited (Andersson 1994;Gross 1996;Rü ppell and Heinze 1999;Rhen and Crews 2002). Nevertheless, the possibility that alternative reproductive tactics are expressed in both sexes (Sinervo and Zamudio 2001) deserves attention in future behavioral and ecological studies of this system of polymorphic electric fishes.…”

“…In most animals alternative mating tactics, and any associated signal differences, are restricted to males (Andersson 1994;Rhen and Crews 2002;West-Eberhard 2003). Notable exceptions are found among social insects with female mating tactics (Rü ppell and Heinze 1999) and in the side-blotched lizard, which exhibits a throat color polymorphism associated with different reproductive tactics in both males and females (Sinervo and Zamudio 2001).…”

Digging beneath the surface: incipient nest characteristics across three species of harvester ant that differ in colony founding strategy

“…Species that found independently tend to be larger than dependentfounding species (Rüppell and Heinze, 1999). Within independently founding species, foundresses that found singly are larger than those that found multiply, as seen in Messor pergandei (Cahan and Rissing, 2005) and other species (Kikuchi et al, 1999;McInnes and Tschinkel, 1995;Rüppell et al, 1998).…”