During sex, the male inserts these spines into a pair of pockets present in D. In the nematode worm Caenorhabditis nigoni, females mate with multiple males. Most worms are hermaphrodites who fertilize their own eggs. The genital mismatch, then, seems to serve as an after-the-fact way to limit hybridization. Toads spend the first part of their lives in the water.Sperm competition is fierce, and sperm have evolved to be very aggressive. Beetles who try it are more likely to die or to be rendered sterile. As tadpoles, they have gills and tails, adapted to swimming.
It involves having sex with a second species, the Mexican spadefoot toad.Mexican tadpoles develop faster than Plains tadpoles, while Mexican-Plains tadpoles develop at an intermediate rate.Where water is limited, hybrid tadpoles are more likely to survive than purebred Plains tadpoles. briggsae hermaphrodites’ life span was reduced, as was their fertility. briggsae hermaphrodites seemed able to anticipate this harm. nigoni males, they could be observed crawling in the opposite direction, as if trying to get away.Only later, at metamorphosis, do they develop lungs.Or sex organs may be produced on the very same individual but different places apart, and in this case the species is said monoicous (in parallel to monoecious in flowering plants).Where sex functions can be expressed on the very same plant (monoicous species), there is some more diversity that furthers the jargon: when sexual structures are clearly separated in different clusters, that’s when sex clusters are found on different ramets from the same individual).Plains spadefoot females apply this strategy selectively.When times are good, they prefer males of their own species. Many females choose Mexican spadefoot mates and produce hybrid young. Mexican-Plains hybrids don’t make very good specimens.Because of instances of clonality, which can locally be fairly important, some moss species are naturally selfing at high rates without the need to evolve specialized sex structures.Of course, they need clonality and genetical loneliness in the environment to do so, but it doesn’t seem to be that uncommon.