Tokudaia muenninki Johnson 1946

Tokudaia muenninki Johnson 1946, Proc. Biol. Soc. Wash., 59: 170.

Type Locality: Japan, Ryukyu Isls (= Nansei Isls), N Okinawa Isl, Hentona (western coast).

Vernacular Names: Okinawa Island Spiny Rat.

Distribution: Known by modern specimens from N Okinawa, and late Pleistocene and Holocene samples from Okinawa and adjacent island of Le-jima (Kawamura, 1989; Kowalski and Hasegawa, 1976).

Conservation: IUCN – Critically Endangered.

Discussion: Originally described as a subspecies of T. osimensis (Johnson, 1946 a), but chromosomal evidence (2n = 44 for muenninki, 2n = 25 for osimensis), as well as external and cranial morphology distinguish muenninki as a separate species (Kaneko, 2001; Tsuchiya, 1981, Tsuchiya et al., 1989). Based upon molar measurements, Kaneko (2001) suggested that the late Pleistocene specimens identified as T. osimensis by Kowalski and Hasegawa (1976) and Kawamura (1989, 1991, 1994) actually represent T. muenninki and T. osimensis, indicating that both species occurred on Okinawa during late Pleistocene. Kaneko cautioned, however, that the fossils must be reexamined to confirm these possible identifications.

A population of Tokudaia also occurs on Tokuno-shima Isl, south of Amami-oshima and north of Okinawa. Chromosomal distinctions between osimensis (2n = 25) from Amami-oshima, muenninki (2n = 44) from Okinawa, and the population from Tokuno-shima Isl (2n = 45) were documented by Honda et al. (1978), Tsuchiya (1981) and Tsuchiya et al. (1989). While that data suggested the Tokuno-Shima Isl sample to represent a third species, Kaneko unfortunately could not include the population in his morphometric study because it is protected and no voucher specimens have been preserved. Significant differences between samples from Tokuno-shima and Amami-oshima in mtDNA cytochrome b sequences and restriction fragment length polymorphism in the nuclear ribosomal RNA gene also led Suzuki et al. (1999 a) to regard the two insular populations as independent species. Molecular data from T. muenninki and morphological information from the population on Tokuno-Shima Isl must be analyzed to test the results implied by present chromosomal information.