Three new species of octothecate pheretimoid earthworms from Taiwan, with discussion on the biogeography of related species

Abstract

Three new species of octothecate Metaphire pheretimoid earthworms are described from Taiwan. They have close phylogenetic relationships with five described species, Metaphire paiwanna, Metaphire bununa, Metaphire riukiuensis, Metaphire taiwanensis, and Amynthas formosae. These eight species are all octothecate. They have similar body size, colour, prostate glands and caeca, and the seven species belonging to the genus Metaphire have C‐shaped male pores. Excluding M. riukiuensis, which has been found only in the Ryukyu Islands, the other seven species are endemic species in Taiwan. Each of them has a distinct geographical distribution. Accordingly, we inferred that the ancestor of these eight species, including M. riukiuensis, came to Taiwan from the continent of East Asia during the Pleistocene. A few of their descendants went northward to the Ryukyu Islands and were isolated. The others remained in Taiwan, dispersed, and were isolated by geographical barriers such as mountains and rivers. Subsequent allopatric speciation events in Taiwan and in the Ryukyu Islands then generated these eight species.