Population structure and sociogenetic organisation in a species with ergatoid queens, the desert ant Ocymyrmex robustior

Abstract

In ants, reproductive division of labour is typically associated with queen-worker dimorphism. In some species with ergatoid queens (wingless worker-like queens), this polymorphism is drastically reduced and virgin queens may integrate the worker force. While ergatoid queens have been described in several species, their colony and population genetic structure remain largely unstudied. Here, we investigated the population structure and sociogenetic organisation of the desert ant Ocymyrmex robustior. All Ocymyrmex species have only ergatoid queens that are worker-sized. Workers, queens, and males from a large population were genotyped at ten polymorphic microsatellite loci. Our results show that the study population is genetically structured, consistent with dependent colony foundation. Genetic analyses revealed that 17.6% of the males were diploid; diploid males are fertile, siring triploid females. Nests were typically headed by a single queen, and queens were strictly monandrous. However, several nests in the population shared matrilines, indicating polygyny, polydomy, dependent colony foundation, serial polygyny, or a combination of these processes. Dissections reveal that workers lay eggs in both queenright and queenless nests, while virgin ergatoid queens lay eggs in queenright nests only. However, our genetic analyses show that male offspring in queenright nests are all queen-produced, suggesting worker policing and/or trophic egg laying.

Facing lethal temperatures: Heat‐shock response in desert and temperate ants

“…Colonies of desert species studied are headed by a single queen (monogyny) and queens are polyandrous (multiple mated), except for O . robustior in which queens are strictly monandrous (de Pletincx & Aron, 2020 ; Lecocq de Pletincx et al, 2019 , 2021 ; Leniaud et al, 2015 ). The two temperate species studied are facultatively polygynous (with a single or several reproductive queens per colony); F .…”

“…Finally, the two temperate ant species, Formica fusca and Myrmica sabuleti, were chosen as comparative nondesert outgroup genera, as they belong, respectively, to the Formicinae (same subfamily as Cataglyphis and Melophorus) and the Myrmicinae (same subfamily as Ocymyrmex). Colonies of desert species studied are headed by a single queen (monogyny) and queens are polyandrous (multiple mated), except for O. robustior in which queens are strictly monandrous (de Pletincx & Aron, 2020;Lecocq de Pletincx et al, 2019Leniaud et al, 2015). The two temperate species studied are facultatively polygynous (with TA B L E 1 Main thermal characteristics of species' natural habitats.…”

Facing lethal temperatures: heat shock response in desert and temperate ants

“…Both these species inhabit temperate areas with AMT of 10.2°C and MaxT of 22.8°C. Colonies of desert species are headed by a single queen (monogyny); queens are polyandrous (multiple mated), except for O. robustior where queens are strictly monandrous [69][70][71][72]. The two temperate species studied are facultatively polygynous (a single or several reproductive queens per colony); F. fusca is facultatively polyandrous, no information about queen mating frequency is available for Myr.…”