Detailed look at hybridogenic reproduction methods on a community scale among desert ants

The vast majority of animals reproduce through sexual intercourse: fertilizing an egg with a sperm cell. However, some rare species have evolved alternative reproduction methods.

Amongst these, one of the most unusual methods is the hybridogenic mechanism used by some species of fish, stick insects, and frogs. In these species, mating takes place between males and females of different species or genetic lineages, meaning that all offspring are therefore hybrids. Young females then undergo a rare genetic occurrence. Their somatic cells contain both maternal and paternal genes, as is the case with species that mate through standard sexual reproduction. However, they eliminate the paternal genes when creating ova, meaning that only the mother's genes are carried forward. In other words, females pass on the female genome alone to future generations.

The Behavioral and Evolutionary Ecology Service led by Serge Aron at Université libre de Bruxelles, in partnership with a research team at CSIC Seville (Spain) have for the first time analysed hybridogenic reproduction methods on a community scale among a species of desert ant, Cataglyphis hispanica.

Like other social hymenopterous insects (bees, wasps, bumble bees), ant communities are characterised by the existence of two casts of female: fertile queens and generally sterile workers who carry out tasks necessary for the day-to-day success of their society.

Through genetic analysis of populations belonging to this species, scientists have shown that sexual partners always belong to two distinct and interdependent genetic lines. The queens then produce hybrid sterile worker descendants: the result of crossing the two lines. However, the queens clone themselves to produce fertile females (future queens). Male offspring also develop from unfertilized eggs, and share the same genetic lineage as their mother. A result of this is that only maternal genes are passed on from one generation to another. This reproduction strategy is a form of social hybridogenics, whereby queens use sexed reproduction to provide their societies "somatic" growth (production of workers), and asexual reproduction for the "fertile" line (sexed reproduction). This strategy has significant evolutionary implications.