Two cryptic species of the phytophagous ladybird beetle Epilachna vigintioctopunctata (Coleoptera: Coccinellidae) detected by analyses of mitochondrial DNA and karyotypes, and crossing experiments.
Analyses of a part of mitochondrial cytochrome c oxidase I gene sequences (645 bp) for seventeen individuals of Epilachna vigintioctopunctata (Fabricius) from eight localities in east and southeast Asia revealed that the populations are divided into two genetically distinct groups (Chiba, Tokyo, Naha, Iriomote, Bangkok vs. Kuala Lumpur, Padang, Bogor). The number of nucleotide substitutions between sequences of different groups was 57-60, while that between sequences within each group was 1-8. Karyotypes of the two groups were also distinctly different. Crossing experiments showed that there exist strong postmating barriers between the two groups: eggs obtained from between-group crossings usually did not hatch, whereas more than 90% of eggs from within-group crossings hatched. It is concluded that E. vigintioctopunctata, a notorious pest of solanaceous crops in Asia and Australia, is composed of at least two reproductively isolated biological species that probably occupy different geographic ranges.