Worker-queen dimorphism and queen winglessness in Megalomyrmex Forel, 1885
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Date
2021-05
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The Ohio State University
Abstract
The evolutionary success of eusocial insects, such as ants, is attributed to their division of labor between reproductive and non-reproductive castes. For most ant species, reproduction is carried out by winged queens. However, for some species, ergatoid queens (wingless queens) – with intermediate morphologies between winged queens and workers – have replaced winged queens. In the ant genus Megalomyrmex Forel, 1885, 16 of the 45 species described have ergatoid queens. As a consequence of flight loss, wingless queens are dependent on their parent colony when founding. They disperse on foot with a subset of their sisters from their natal nest (i.e., budding). In Megalomyrmex, queen winglessness has been gained and lost multiple times throughout its evolutionary history and in the instance of four species, it may occur simultaneously with the winged queen strategy in the same species. Using extensive morphological measurements, we examine worker-queen dimorphism of wingless queens in Megalomyrmex. These include measurements of the head, eyes, mesosoma, and metasoma. Focusing primarily on the head and eye morphology, we explore the relationship of these traits between castes within the genus. Our findings support the established trend that winged queens are typically larger while ergatoid queens are more worker-like. Additionally, we find that the eyes of winged queens are larger than that of ergatoid queens relative to their body size, which may suggest a similar relationship between winged and ergatoid queens with regards to eye morphology. Our study contributes to the growing body of knowledge on ergatoid queen evolution, as well as the evolutionary relationship between morphology, natural history, and colony reproduction.
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Keywords
evolution, ant, morphology, winglessness, worker, queen