>>57430783>how female only pokemon survives as a speciesEgg groups.
Furthermore, Females almost always replicate another of their own species as the Pokemon produced by breeding is determined by which of the Pokemon is female.
If anything, this question should be asking how it is that Male onlies survive, but the answer there is obvious. There are certain female only Mon that are essentially a counterpart of a male only Mon, for example the Nidorans or Miltank/Tauros or Mandibuzz/Braviary who can breed for a 50-50 chance of either Mon being the resulting offspring.
If anything, it's a wonder how Pokemon like the Hitmon trio or Throh and Sawk who have no female equivalent manage to produce offspring in a nature setting since they can only breed with Ditto.