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Abstract:
In ants, which are all eusocial, social polymorphism exists in the form of a variable number of queens. The occurrence of colonies with a single queen (monogynous) or multiple queens (polygynous) within a species is found in about 15% of ant species, offering various model systems to assess the life-history differences between the two social forms. Polygynous colonies are assumed to be better competitors due to larger colony size and higher colony growth, whereas monogynous colonies are supposed to rely on a colonizer strategy as they are founded solitarily by larger winged queens that disperse by flight. The ant Myrmecina graminicola harbors a social polymorphism associated with a wing polymorphism in queens, both being determined by a different supergene with monogynous queens being mostly winged and polygynous queens being always apterous. By comparing colonies sampled in the same population, we showed that polygynous colonies with apterous queens and monogynous colonies with winged queens did not differ in the number of workers and larvae at the time of collection. Accordingly, once reared in the laboratory, these colonies produced a similar number of pupae and adults (workers or sexual individuals), probably from the larvae already present at the time of collection. However, polygynous colonies produced more eggs and new larvae in the laboratory than their monogynous counterparts. We discuss why this larger brood production of polygynous colonies was not reflected by a larger colony size in the field, and what the consequences of similar colony growth and productivity between the social forms would mean for the maintenance of genetic polymorphisms.