So a paper came out on September 3rd that is novel and wild, and I'd like to break it down.
Sex determination is a complex process that varies from species to species. Humans the XY sex-determination system, where the presence of the Y chromosome results in a male. The opposite system, the ZW sex-determination system in insects and birds, has females as the presence of the W chromosome, whereas males are the homogametic sex, with ZZ.
Ants, on the other hand, use what is called haplodiploidy for sex determination. Unfertilized eggs develop as males and only contain one copy of each chromosome, whereas fertilized eggs develop as females and contain two copies. This, in and of itself, is quite weird (though not quite as weird as the entire haplodiplontic life cycle), but is present across all ants, wasps, bees and such.
The paper first finds that the queens of Messor ibericus are unable to produce workers without mating with a male of a separate species, M. structor. This, although uncommon, is not unprecedented; there's a wide variety of strategies on the spectrum of parthenogenesis, ranging from incorporating genetic material from a different species (hybridogenesis), to requiring the presence of sperm but not the genetic material (gynogenesis), to not requiring mating at all (parthenogenesis). So obligate hybridogenesis is not unexpected, at least for the production of workers; queens can still be produced without mating with a different species.
But M. ibericus exists in regions where M. structor doesn't, and yet still produces hybrid workers.
Looking more closely at these colonies, they found two phenotypic variants of males: one hairy, one less so. The less hairy males were genetically identical to M. structor, but their mitochondrial DNA matched that of M. ibericus, indicating that the egg was laid by M. ibericus. Which implies that M. ibericus queens are capable of laying eggs that only contain the DNA of the sperm from M. structor males.
Since the DNA of the males is identical to that of the sperm the queen was fertilized with, these males are actually clones of the sperm. This is a rare form of androgenesis, or male cloning, as males generally do not produce eggs and thus often parasitize the eggs of other species in order to clone themselves.
And so, in environments where M. structor does not exist, M. ibericus queens can clone M. structor males from stored sperm and mate with them to ensure a population of M. structor sperm with which to lay hybrid workers.
There is a question of who is exploiting whom. The M. ibericus appears to have domesticated M. structor, cloning its sperm to create clones of itself. But at the same time, M. structor is using M. ibericus to propogate clones of itself, passing down its own genetic information instead. It seems that both species are exploiting each other, a mutual invasion leading to a form of cooperation.
Novel and intriguing. Endless forms most wonderful.