Caste-specific quantitative genetics and phylogenetic signal analysis revealed the morphological adaptation of Asian weaver ant, Oecophylla smaragdina (Hymenoptera, Formicidae)

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 well-developed 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.