Decoupled evolution of mating biology and social structure in Acromyrmex leaf-cutting ants

• Published in: Behavioral ecology and sociobiology 2022, Vol.76 (1), Article 7
• Main Authors: Dahan, Romain A., Grove, Nathan K., Bollazzi, Martin, Gerstner, Benjamin P., Rabeling, Christian
• Format: Article
• Language: English
• Subjects: Acromyrmex; Animal Ecology; Animal reproduction; Ants; Behavior; Behavioral Sciences; Biological evolution; Biology; Biomedical and Life Sciences; Colonies; Eusociality; Evolution; Genetic diversity; Genetic markers; Genetic variability; Insects; Leaves; Life history; Life Sciences; Markers; Mating behavior; Microsatellites; Nesting; Original Article; Polyandry; Polygyny; Queens; Reproductive behavior; Social conditions; Species; Zoology
• ISSN: 0340-5443; 1432-0762
• DOI: 10.1007/s00265-021-03113-1

Insect societies vary greatly in their social structure, mating biology, and life history. Polygyny, the presence of multiple reproductive queens in a single colony, and polyandry, multiple mating by females, both increase the genetic variability in colonies of eusocial organisms, resulting in potential reproductive conflicts. The co-occurrence of polygyny and polyandry in a single species is rarely observed across eusocial insects, and these traits have been found to be negatively correlated in ants. Acromyrmex leaf-cutting ants are well-suited for investigating the evolution of complex mating strategies because both polygyny and polyandry co-occur in this genus. We used microsatellite markers and parentage inference in five South American Acromyrmex species to study how different selective pressures influence the evolution of polygyny and polyandry. We show that Acromyrmex species exhibit independent variation in mating biology and social structure, and polygyny and polyandry are not necessarily negatively correlated within genera. One species, Acromyrmex lobicornis , displays a significantly lower mating frequency compared to others, while another species, A. lundii , appears to have reverted to obligate monogyny. These variations appear to have a small impact on average intra-colonial relatedness, although the biological significance of such a small effect size is unclear. All species show significant reproductive skew between patrilines, but there was no significant difference in reproductive skew between any of the sampled species. We find that the evolution of social structure and mating biology appear to follow independent evolutionary trajectories in different species. Finally, we discuss the evolutionary implications that mating biology and social structure have on life history evolution in Acromyrmex leaf-cutting ants . Significance statement Many species of eusocial insects have colonies with multiple queens (polygyny), or queens mating with multiple males (polyandry). Both behaviors generate potentially beneficial genetic diversity in ant colonies as well as reproductive conflict. The co-occurrence of both polygyny and polyandry in a single species is only known from few ant species. Leaf-cutting ants have both multi-queen colonies and multiply mated queens, providing a well-suited system for studying the co-evolutionary dynamics between mating behavior and genetic diversity in colonies of eusocial insects. We used microsatellite markers to in