Host shift result in adaptive radiation in the phytophagous ladybird beetles, genus Henosepilachn

      Adaptation to different environments can promote population divergence and speciation. If a population shifts the habitat to different niche and if it results in divergence in the reproductive characters, it would cause speciation between populations inhabiting two distinct habitats. Although this process known as ‘host shift’ is key to understand speciation, the direct observation of host shifting event is very rare since it generally occurs in short evolutionary time. The phytophagous ladybird beetles of the genus Henosepilachna are rare examples for the rapid diversification with shifting their host plants. Specifically, two cases of host-specific species/population pairs of Henosepilachna are the most obvious cases of current host shift correlating to speciation. I review the unique speciation mode in this group and suggest hypothetical mechanism of the diversification based on recent empirical data.