THE CURVE. “These may seem exceptions, but considering what is shared and what is distinct between closely aligned species with two sexes vs. those with more, or those with only one (unisexual, to mean “uni” as in one sex, or “universal” as in pansexual and capable of mating with any other member of the population as well as itself), may prove enlightening.”
http://www.sciencedirect.com/science/article/pii/S1749461315000391