Speciation by hybridization: the mind-boggling nature, educational, and research value of the largest group of unisexual vertebrates.

Thirteen species of North American lizards are remarkable because only females exist, which reproduce by cloning unfertilized eggs. Their closest relatives reproduce sexually, with eggs fertilized by sperm from males, as in most vertebrates. The unisexual species originated through hybridization, dispensing with sex and males in a single generation. These lizards hold tremendous potential in science education as a fascinating model for learning about fundamental biological concepts, and in research for developing knowledge with medical applications for reproductive biology, embryonic development, and genetic interactions. These lizards maintain genome integrity in a hybrid state in which recombination is absent, but do not suffer from conditions or disorders such as Down's Syndrome or cancer that are caused by aneuploidy in humans. The multifarious impacts of hybridization on the diversity of species in this group present an exceptional opportunity to deepen understanding of the complicated process of evolutionary diversification.