INTRODUCTION

The taxonomic status of several Myotis species has recently been revised (Benda and Tsytsulina, 2000; Tsytsulina, 2001), but the genus still includes taxa with doubtful status. One of these is Myotis abei, described by Yoshikura (1944) from south-east Sakhalin, Shirotoru town (now Makarov). The species is known only from the type locality and a single type specimen. Originally, the specimen was deposited at the Yamashina Institute for Ornithology and Zoology (Tokyo), but was later moved to the National Science Museum in Tokyo (collection number M-5840 o.5371). The skull of the specimen was lost during the transfer and now the type is represented only by a dry skin specimen.

Yoshikura (1944) described M. abei as a form of ‘hohohige kaumori’, a whiskered bat in Japanese, and noted its similarity to M. mystacinus gracilis Ognev, 1927. Later he named it in English as Abe's whiskered bat (Yoshikura, 1956), i.e. belonging to the subgenus Selysius. In the original description of the species, Yoshikura (1944) pointed out that the wing membrane was attached to the proximal part of metatarsus, as in Myotis dasycneme. It is recognised that the attachment of the wing membrane to the base of the first toe is a characteristic feature of the subgenus Selysius, whereas insertion to the metatarsus (M. daubentoni, M. capaccini, M. dasycneme and others) and tibia (M. macro-dactilus) is a characteristic feature of the subgenus Leuconoe (e.g., Tate, 1941; Koopman, 1994). Nevertheless, subsequent taxonomic revisions placed M. abei in different sections within Myotis, and usually provided no comment on the reasons for such placements. Ellerman and Morrisson-Scott (1951, 1966) included M. abei in Myotis incertae sedis. Imaizumi (1954) included M. abei in his key to east Asian species of Myotis, but did not make any comment about this species. According to this key, the only difference between M. abei and M. daubentoni is the wing membrane insertion: attachment to the ankle in M. abei, and to the middle of the metatarsus in M. daubentoni. Later, in his synopsis of Japanese whiskered bats, Imaizumi (1958) did not mention M. abei at all. This implies that Imaizumi did not recognise M. abei within Selysius. Yoshikura (1956) listed M. abei along with M. mystacinus gracilis, M. ikonnikovi and M. daubentoni ussuriensis in the revision of insectivores and bats of Sakhalin. Besides measurements, he listed six qualitative characters that distinguish these three species. Myotis abei differs from M. daubentoni in three of them. These characters are: location of the wing membrane insertion (to the ankle in M. abei, and to the middle of metatarsus in M. daubentoni), relative size of the tarsus to the tibia (about half as long in M. abei, and decidedly more than half as long in M. daubentoni) and colour of ventral pelage (slaty black in M. abei and gray in M. daubentoni). Measurements were given only for single specimens of both M. abei and M. daubentoni.

Corbet (1978) did not indicate subgeneric membership, but placed M. abei together with M. mystacinus, M. brandtii and M. ikonnikovi. Pavlinov and Rossolimo (1987) considered the taxonomic status of M. abei as unclear. In her book about Japanese bats Yoshiyuki (1989) did not provide any comments about M. abei. Koopman (1993) treated M. abei as a member of the subgenus Leuconoe and later in the more detailed publication (Koopman, 1994), placed M. abei in the daubentoni group. Pavlinov et al. (1995) placed M. abei in Leuconoe incertae sedis, but noted that the taxonomic status of the species was unclear. Horachek et al. (2000) suggested that M. abei is conspecific with M. brandtii. In 2002, Pavlinov et al. included M. abei in the subgenus Leuconoe, but also noted that the taxonomic status and morphological features of M. abei were unclear and the species appeared to resemble M. daubentoni. The present study sought to clarify the position of the type specimen by comparing it with specimens of other Myotis.

MATERIALS AND METHODS

The type specimen of M. abei was examined and compared with 46 specimens of M. daubentoni, 52 M. macrodactylus, 24 M. pruinosus, 76 M. ikonnikovi, and 71 M. brandtii gracilis from Japan and adjacent territories (Appendix 1). Myotis pruinosus was also included in the comparison as a representative of the subgenus Leuconoe, despite of distribution limited by Honshu, and also because of its small size. Measurements including forearm length, tibia and tarsus length, and condylo-basal cranial length were taken from adult specimens. Coloration was studied in all available specimens (i.e. irrespective of age).

RESULTS AND DISCUSSION

In small Myotis species the location of the wing membrane is an important diagnostic character for species identification. Within the considered species, the wing membrane is attached to the metatarsus in M. daubentoni, to the tibia in M. macrodactylus, and to base of the first toe in M. pruinosus, M. brandtii and M. ikonnikovi. The type specimen of M. abei exhibits wing membrane attachment to the upper half of the metatarsus, but in close proximity to the metatarsal articulation. The size ratio of the tarsus and metatarsus is also used to characterise subgenera within Myotis. In the subgenus Leuconoe, the combined length of tarsus and metatarsus is equal to or greater than half of the tibia length, whereas in the subgenus Selysius it is less than half (Table 1). In the type specimen of M. abei this ratio is within the range of M. daubentoni (Table 1).

Table 1

Measurements and characteristic features of M. abei and 5 considered Myotis species.

Contrast is evident in the coloration of the dorsal and ventral pelage in the M. abei specimen, one of the features characteristic of M. daubentoni, whereas in the other considered species there is no such a contrast (Table 1). The type specimen of M. abei has brown dorsal fur, in clear contrast to the lighter fur on the ventral surface (as in M. daubentoni, Fig. 1). Yoshikura (1944, 1956) described the colour of the ventral pelage of the type specimen as ‘slaty black’, whereas it is evidently light grey on the type specimen. While fur colour can change during long storage in museums, it seems unlikely that a dry preserved specimen would change colour on one side only (the dorsal pelage remains dark).

Fig. 1

Type specimen of M. abei YOSHIKURA, 1944 (NSMT M-5840 o.5371), views from below (A), above (B), and magnified view of wing articulations (C).

In both publications concerning M. abei, Yoshikura (1944, 1956) noted that the type specimen was an adult male. However, it is evident that the specimen is a subadult since the wing epiphyses have not yet calcified (Fig. 1, C). Even as a subadult, the specimen has a forearm length within the range characteristic of M. daubentoni (Table 1). Only two samples of M. daubentoni from Sakhalin were included in our study, however detailed analysis of geographic variation in M. daubentoni in the Russian Far East was made by Tiunov (1997). He demonstrated that Daubenton's bats from Sakhalin belong to the subspecies M. daubentoni ussuriensis Ognev, 1927 and do not differ in their basic external and selected cranial measurements from M. d. ussuriensis from other localities (Tiunov, 1997). Furthermore, qualitative characters such as type of wing membrane insertion, pelage colour, and the tarsus-metatarsus ratio of Sakhalin's M. daubentoni are within the characteristic range of M. daubentoni (M.P. Tiunov, personal communication, Table 1). Maeda (1985) analysed skull and external measurements in M. daubentoni in Hokkaido, Sakhalin, Iturup Is. and Korea and did not find any significant differences between sex and populations.

In terms of cranial measurements, the condylo-basal length shown by Yoshikura (1944, 1956; which was not measured in the present study due to missing skull), is smaller and outside the size range of adult M. daubentoni. It is well known that skull grows slower than limb bones, i.e. it reaches its definitive size slowly than forearm (e.g. Swarthz, 1997), therefore the measurement of condylo-basal length in the subadult specimen of M. abei might be of little use. Taking the conflicting observations into consideration (age of the specimen, pelage coloration, the wing membrane insertion), we believe that the description of M. abei as a distinct species is a result of misidentification. The specimen preserved in the National Science Museum (Tokyo) and recognised as the type specimen of M. abei is actually M. daubentoni. Thus, M. abei should be considered as a junior synonym of M. daubentoni.