Facultative use of thelytokous parthenogenesis for queen production in the polyandrous ant Cataglyphis cursor

Abstract

The evolutionary paradox of sex remains one of the major debates in evolutionary biology. The study of species capable of both sexual and asexual reproduction can elucidate factors important in the evolution of sex. One such species is the ant Cataglyphis cursor, where the queen maximizes the transmission of her genes by producing new queens (gynes) asexually while simultaneously maintaining a genetically diverse workforce via the sexual production of workers. We show that the queen can also produce gynes sexually and may do so to offset the costs of asexual reproduction. We genotyped 235 gynes from 18 colonies and found that half were sexually produced. A few colonies contained both sexually and asexually produced gynes. Although workers in this species can also use thelytoky, we found no evidence of worker production of gynes based on genotypes of 471 workers from the six colonies producing sexual gynes. Gynes are thus mainly, and potentially exclusively, produced by the queen. Simulations of gynes inbreeding level following one to ten generations of automictic thelytoky suggest that the queen switches between or combines thelytoky and sex, which may reduce the costs of inbreeding. This is supported by the relatively small size of inbred gynes in one colony, although we found no relationship between the level of inbreeding and immune parameters. Such facultative use of sex and thelytoky by individual queens contrasts with other known forms of parthenogenesis in ants, which are typically characterized by distinct lineages specializing in one strategy or the other.

Fertile diploid males in the ant Cataglyphis cursor: a potential cost of thelytoky?

“…Four colonies were excavated in Argelès at the beginning of June 2006, seven were collected in the same locality at the end of May 2007 and seven were excavated from Saint Cyprien (9.5 km from Argelès) at the end of May 2007 (Table 1, see also Doums et al 2013 for details on colonies collected in 2007). All colonies showed sexual activity at the nest entrance, where non-natal males were seeking mates (Lenoir et al 1988;Cronin et al 2011) and indeed all contained gynes (young queens).…”

“…An additional sample of 265 workers from the seven colonies that produced diploid males was genotyped at six microsatellite loci (multiplex 1 and 2). The genotype of workers was already published for one of these colonies, col54 (dryad 10.5061/dryad.5488t; Doums et al 2013).…”

“…Individuals from the four colonies collected in June 2006 were genotyped at six microsatellites (multiplex 1 and 2) (Clémencet et al 2005). The mode of queen production in these four colonies was determined following Doums et al (2013); the presence of the queen was determined after ovary dissection and observation of yellow bodies, as many gynes had already lost their wings but did not start egg-laying. In one of the four colonies, the mother queen was not found and her genotype was inferred from her parthenogenetically produced gynes.…”

“…PCR conditions were identical to those described in Doums et al (2013). Amplification products were loaded together on an ABI Prism 310 sequencer (Applied Biosystems) and allele sizes were estimated using Genescan software.…”

“…Individuals from the 14 colonies collected in May 2007 were genotyped at 12 microsatellites (multiplex 1 and 2: cc11, cc26, cc46, cc63, cc76, cc89; multiplex 3 and 4: cc51, cc58, cc61, cc65, cc99, cc100; Doums et al 2013). Queen and gyne genotypes as well as the mode of gyne production (by thelytoky or sexual reproduction) were retrieved from Doums et al (2013) (the data file can be found in dryad database ref: dryad10.5061/dryad.5488t). Males were specifically genotyped for this study.…”