Parthenogenetic Reproduction in Strumigenys Ants: An Update

Parthenogenetic reproduction is a common feature for social Hymenoptera, as males typically develop from unfertilized eggs (arrhenotoky). Production of female offspring without the involvement of sperm (thelytoky) also exists but is rather exceptional as it has been reported for only 16 ant species so far. Three of these belong to the genus Strumigenys: S. hexamera, S. membranifera and S. rogeri. Our observations on the reproductive biology in various Oriental Strumigenys species extends this list of thelytokous ants with three more species: S. emmae, S. liukueiensis and S. solifontis. Of these six thelotykous species, S. emmae, S. membranifera and S. rogeri are known as tramp species. Reproduction without the need to fertilize eggs no doubt offers these species a considerable advantage when establishing colonies in new environments. Published histological data on S. hexamera and S. membranifera already showed that the queens possess a functional spermatheca. We now provide evidence that this is also the case for the four other thelytokous Strumigenys species. Retaining a functional spermatheca and reproductive system may keep the queens ready for the exceptional event of mating and hence increase genetic variability, as males do occur very rarely.