[An interesting paper about a beautiful Japanese gigantic earthworm. The results show high intraspecific variation of up to 15.9% for mitochondrial COI gene, which is equivalent to those found previously in many species in Taiwan. This pattern suggests that high intraspecific genetic variation may be a common phenomenon in earthworms. The authors also used molecular clock of 4.8% per million years for COI estimated by Chang et al. (2008) to calculate the divergence time of populations, and the results showed consistency between geological data and clade distribution, providing evidence for this slightly high molecular clock.]
Journal
European Journal of Soil Biology 45 (2009) 423–430
Authors
Yukio Minamiya, Jun Yokoyama, Tatsuya Fukuda
Abstract
To clarify the historical phylogeography of a Japanese earthworm, nucleotide sequence variations of Metaphaire sieboldi were investigated with respect to its geographic distribution. Sequencing of mitochondrial DNA (mtDNA), including the cytochrome oxidase subunit I (COI) region and the 16S rDNA region, of 72 samples including 4 outgroup taxa, and phylogenetic analyses using neighbour-joining (NJ) and Bayesian inference (BI) methods indicated that M. sieboldi forms a monophyletic group. This monophyletic group was divided into seven subgroups; most subgroups comprised individuals from several areas, except for southern Shikoku and southern Kyushu. The phylogenetic tree demonstrated that the Shikoku and Kinki populations were paraphyletic at the basal node, and individuals from Kyushu and western Shikoku were positioned at the advanced group. Estimated phylogeographic events based on mtDNA analyses include (1) M. sieboldi originated in Shikoku and/or Kinki, (2) individuals from Chugoku and Kyushu have a common ancestor from Shikoku, and (3) individuals from western Shikoku originated from Kyushu progenitors (about 0.4–0.5 mya) after separation by rising sea levels.
