Queens of M. ibericus can produce male offspring of the species Messor structor, which is not a sister species, by laying eggs that only contain DNA from M. structor in its nucleus. The nuclear DNA from the egg is removed, only keeping the nuclear DNA of the sperm, resulting in clonal reproduction for the males. This is required because the queen can only produce (female) worker ants using sperm from M. structor, making all workers hybrid. The queen can still create male offspring of her own species, but their sperm cannot produce workers, only queens.[3] The term xenoparity was created to describe this ant, denoting production of offspring of a different species in order to support their life cycle.[3]
Xenoparity has evolved from a form of sperm parasitism or sperm mutualism, in which one species depend on another's sperm for worker production. This relationship is usually disadvantageous for the species having the dependence as it forces them to live in places where the other species is present, but xenoparity appears to be one solution to the problem. (Some populations of M. ibericus have not yet evolved xenoparity and still require the acquisition of a M. structor male from outside the nest.)[3] Among Messor harvester ants, there are many other cases of sperm parasitism. Some have evolved another solution to this problem: reciprocal sperm parasitism, where two species require the sperm from the other species in order to produce workers.[4]
