In eusocial insects, particularly in ants, caste differentiation is extremely complicated when we rely on traditional taxonomy. In most species, the worker caste does not display any distinct morphological characters neither the caste’s central division according to their morphological size variations. We used a landmark-based geometric morphometric approach to quantify the morphological characteristics of female caste systems (queen, major and minor worker ant) of Oecophylla smaragdina. Our findings suggested that each caste has its unique shape and size. Especially in the worker caste, apart from the size variations, we can use the shape as a prominent tool for distinguishing between them. The O. smaragdina exhibits a triphasic allometry pattern. Studying the allometry and non-allometry components of each caste system revealed a highly complex size and shape relationship in the female caste systems. From the allometric and non-allometric analysis, we concluded that the major worker ants showed a closer relationship with the queen than the minor worker ant. This outcome demonstrated that Asian weaver ant exhibits complex shape variations related to size and is correlated to their functional modular characters. This research sheds new light on caste systems’ taxonomic uncertainties for eusocial hymenopteran groups, especially ants.
Insect caste development and their morphological divergence are not yet studied well, especially in ants. However, the role of developmental and genetic integration in evolution is contentious. In our study, we tried to reveal the quantitative genetics selection responses, phylogenetic signal, and evolutionary origin of weaver ant female castes (queen, major and minor). The widening and lengthening of the head region, as well as the welldeveloped mandibular process, are the major heritable characteristics found in the major worker ants. We hypothesized that these conserved and heritable characteristics may help the major worker ants for defense, foraging purposes and other nest-building function aspects. However, in the case of minor worker, small heads and the reduced mandibular process are the more heritable characteristics. Compared to worker ants, in queen, the highly heritable and conserved morphological character is well-developed thoracic regions and large-sized abdomen. It is interesting to note that there is no detectable phylogenetic signal across the female cast of the Asian weaver ants, which suggests that the caste development and morphological divergence are environmentally modulated not evolutionary conserved. From this study, we concluded that caste-specific morphological shape and size are highly conserved traits and these traits are modulated by their niche preferences.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.