Evolutionary History of Ohomopterus

In this chapter, we explore the origin of Ohomopterus based on fossil data and a molecular phylogenetic analysis of the extant taxa using genome-wide sequence data. The fossil data suggest that an ancestral population of Ohomopterus may have existed in the late Miocene through the Pliocene. The divergence time estimation using a molecular phylogeny of the extant species suggests that the most recent common ancestor of Ohomopterus traces back to the beginning of the Pleistocene; since then, they have diverged into five species groups that vary in body size and genital morphology. The basal groups have small, triangular copulatory pieces and small to large body sizes, and the most derived group contains species with highly divergent genital parts and the highest speciation rate among species groups. Although the divergence of Ohomopterus is characterized by the divergence in traits for mechanical reproductive isolation, the occurrence of interspecific hybridization between various species pairs is suggested by the frequent sharing of the same or closely related mitochondrial haplotypes.