A new type of male dimorphism with ergatoid and short-winged males in Cardiocondyla cf. kagutsuchi

Abstract

A new type of ant male dimorphism, consisting of wingless (ergatoid) and short-winged (brachypterous) males, was found in a species of the "Cardiocondyla kagutsuchi"-complex from Malaysia. The ergatoid males show the typical morphological and behavioral characteristics of those of many other Cardiocondyla species. The brachypterous males are morphologically intermediate between ergatoid males and typical winged males of other taxa in this genus. On one hand, they share a number of morphological and behavioral features with ergatoid males that might be adaptations to the loss of flight and intranidal mating: aggressive behavior towards rival males, a prolonged spermatogenesis, which is unique in winged males, paler body coloration, smaller compound eyes, shorter antennal funiculi, more rounded heads -perhaps due to the increased development of mandibular muscles, and an angular pronotum, probably for neck protection. Their short wings appear to protect the petiolar joints during fighting. On the other hand, the brachypterous males have not become as specialized as the ergatoids and to some extent keep the nature of the winged males of other species, i.e., they escape from the nest with a higher probability and with less injuries and do not show a reduction of the ocelli. In the sexual production season, the ergatoid males emerged first in small numbers and then both male morphs emerged in large numbers. The sex ratio was extremely female-biased in the earlier stage of sexual production, probably due to local mate competition.

Wingless and intermorphic males in the ant Cardiocondyla venustula

“…Yamauchi et al (2005) found that intermorphic males of C. cf. kagutsuchi that eclose in the presence of adult rivals have a significantly higher survival rate than wingless males.…”

The Evolution of Alternative Reproductive Tactics in Male Cardiocondyla Ants

“…The occurrence of C. cf. kagutsuchi with “intermorphic” males combining the morphological traits of wingless fighter males and wings suggests that male‐determining mechanisms are not very stable in this taxon (Yamauchi et al 2005). In addition, the high proportion of “sex mosaics” in one C. cf.…”

Decision-making conditions for intra- or inter-nest mating of winged males in the male-dimorphic ant Cardiocondyla minutior

“…Male wing dimorphisms are observed in many species of Cardiocondyla ants, and several patterns of male dimorphisms have been observed, such as the combination of winged and ergatoid males or of brachypterous and ergatoid males, and only ergatoid males (e.g., Bolton, 1982;Kugler, 1983;Seifert, 2003;Yamauchi et al, 2005). In C. obscurior, under good conditions, colonies start to produce ergatoid males, whereas under poor conditions, winged males are produced Heinze et al, 2004;Du et al, 2007;Schrempf and Heinze, 2008).…”

“…The genus Cardiocondyla includes myrmicine ant species that exhibit male dimorphism, with both winged and wingless males (Kugler, 1983;Heinze et al, 1998;Terayama, 1999;Seifert, 2003;Yamauchi et al, 2005). The wingless males are referred to as ''ergatoid'' males due to their very similar external morphologies to workers.…”