Myotis secundus sp. n.

Figures 2, 3, 4d, and 6a

Synonymy. Myotis sp. 2: Lin et al. 2004. Vernacular, unavailable name. Myotis sp. 2: Cheng et al. 2010. Vernacular, unavailable name.

Myotis sp. 2: Ruedi et al. 2013. Vernacular, unavailable name.

Holotype. Adult male collected by C.H. Chou on 8 July 2003 (field number #B030018). The dry skin and skull are deposited in the collections of the Department of Biology, Tunghai University under accession number THUMB 30018. The complete mitochondrial Cyt b gene was sequenced from tissue extracts taken from the holotype and deposited in GenBank under accession number KP187896 and was used in the phylogenetic analyses presented herein (Clade VIII in figure 3).

Paratypes. The identity of all six paratypes listed hereafter was confirmed by both the multivariate morphological (Fig. 2) and genetic analyses (Fig. 3). These paratypes are 5 adult males and 1 adult female from near Kaohsiung City in Taoyuan District collected between 2002 and 2004 (TESRI B0271, THUMB 92, 30017, 30020, 30051–2). The following GenBank accession numbers correspond to the complete mitochondrial Cyt b gene sequenced in these paratypes: KP187889, KP187895 –97, KP187899 –00 (Table 1).

Other referred material. 3 adult males from near Datong Township, Yilan County (TESRI B0273–5); 1 adult female from Fuxing Township, Taoyuan County (TESRI B0272); 3 adult males from near Wufeng Township, Hsinchu County (TESRI B0265, B0267, B0268); 2 adult male and 1 adult female from near Taichung City, Heping District (NMNS t-3474, TESRI B0270, THUMB 30013); 1 adult male and 1 adult female from near Yuli Township, Hualian County (THUMB 30023, 30031); 2 adult females and 1 adult male from Taoyuan District, Kaohsiung City (THUMB 30053, 30016, 30019); 1 adult male from Yuli Township, Hualian County (THUMB 30055); 1 adult male from Donghe Township, Taitung County (TESRI B0269).

Type locality. The designated type series originate from the forest areas near Kaohsiung City (Taoyuan District) in south-central Taiwan ROC (approximate coordinates: 23°08’ N, 120°48’ E).

Distribution. M. secundus sp. n. has so far only been recorded in Taiwan, where it is relatively common and widespread in forested habitats across most of the central regions. It was found near locations 1- 4, 7, 15, 17, 19, 21 and 21 (Fig. 1).

Etymology. We name it secundus (meaning second in Latin), as it was the second unnamed taxon found in Taiwan and initially mentioned under the name Myotis sp. 2 (Chou 2004; Lin et al. 2004; Cheng et al. 2010; Ruedi et al. 2013). In the photographic guide to the bats of Taiwan (Cheng et al. 2010), it was illustrated under the vernacular name of Long-toed Myotis, although this attribute is not particularly developed in this species.

Measurements of the holotype. Measurements are in mm. Head and body length, 37; tail length, 41; forearm length, 35.7; hind foot length (including claw), 7.1; tibia length, 17.5; thumb length, 6.6; ear length, 12.8; tragus length, 6.2; greatest skull length, including incisors, 14.1; greatest zygomatic breadth, 8.4; postorbital breadth, 3.3; mastoid breadth, 6.7; greatest braincase width, 6.3; upper canine-molar toothrow, 5.4; width across upper canines, 3.4; width across 3rd upper molars, 5.6.

Diagnosis. Small-sized Myotis (weight 3–5 g) with dark brown pelage color, slightly lighter ventrally, without demarcation between dorsal and ventral sides. Face and ears dark brown becoming more flesh-colored near the base of ears and above the eyes. Wing membranes attached to base of outer toe. Feet about half tibia length. Tail approximately same length as head and body length. Ears relatively long and narrow with a slight notch on the proximal third of the rear edge of conch. Tragus elongated and narrow, reaching the ear notch. Skull profile slender and relatively angular, with nearly flat braincase apex and abruptly falling posterior parts (Fig. 6 a); frontal part of braincase gently rising from rostrum to the top. Anterior part of the rostrum narrow and convergent. Teeth relatively robust with upper premolars aligned in toothrow and all visible in side view (Figs. 4d, 6a). The second upper and lower premolars are distinctly smaller than corresponding first premolars. Canines relatively strong, slightly larger than premolars. All lower molars are myotodont.

Description. This small Myotis has a long, shaggy and very dark brown pelage, with a tinge of lighter brown color at hair tips, giving a frosted appearance to its fur (unlike e.g., M. yanbarensis). The underparts are lighter, buffier, also with pale brown hair tips. The face is densely haired, with a small bare part located above the eyes (Cheng et al. 2010). The patagium is essentially naked and dark brown, with wing membrane attaching to the base of outer toe. The ears are relatively long and narrow, with a small but distinct notch. The tragus is narrow, straight, slightly bent forward close to the tip; it extends to about a third of the distance to the tip of ear. Feet (about 7–9 mm, including claw) and thumbs are slender, both with sparse guard hairs and slender claws. The tibia is long (16–17.7 mm). Tail (about 40 mm) is as long as head and body length.

When viewed in profile (Figs. 4d, 6a), the braincase of the skull has gently rising frontal parts, and is nearly flat on its summit; the occipital region is rounded, smooth with no visible crests. The frontal part of the rostrum is narrow and, in front of the canines, is convergent. Mean and range of external and skull measurements of M. secundus sp. n. from Taiwan are given in Table 4.

Dental formula I 2 /3 C 1/1 PM 3/3 M 3/3, comprising the adult dentition of 38 teeth. The teeth are not particularly weak, although the canines (both upper and lower) are only slightly higher than the corresponding last premolars (Figs. 4d, 6a). The second incisor is clearly smaller than the first (in lateral view), although in occlusal view both are of similar basal dimensions. All premolars are in the toothrow and visible in lateral view, but the second one (both upper and lower) is much smaller than the first one (Fig. 4d). The third upper premolar has a distinct paraconule. Lower molars are all myotodont.

Comparisons. In recent taxonomic accounts (e.g., Corbet & Hill 1992, Simmons 2005), a single small species of Myotinae was found on Taiwan and was called Myotis muricola latirostris (see above for its current taxonomic position). However, since 2004, bat surveys showed that a second small (weight 3–5 g), relatively common Myotis species, that was not fitting the characteristics of latirostris, was living in various habitats of the island. It was referred subsequently as Myotis sp. 2, and hence named here M. secundus sp. n. Although both species are indeed small and have a dark, almost black dorsal pelage, the new species is easily distinguished from S. latirostris by its larger external dimensions such as thumb or tibia length, or by mostly larger skull dimensions as well (Table 4). M. secundus sp. n. has myotodont lower molars, whereas they are nyctalodont in S. latirostris. This character also distinguishes the new species from other small, blackish Myotis from continental Asia pertaining to the siligorensis group, such as M. siligorensis, M. badius, M. alticraniatus, etc. (see Tiunov et al. 2011). Another small Myotis living in south-east China and described originally as M. sowerbyi (Howell 1926), is also very similar to M. secundus sp. n. (similar external dimensions, wing insertion to the base of the toes, myotodont lower molars), but is clove-brown, not blackish, has much more slender upper (Fig. 8 b) and lower canines, has a first lower premolar nearly as large as the canine (it is only half its size in M. secundus sp. n., Fig. 4d), and in skull profile it has a more inflated and elevated braincase and rostrum (Fig. 6 b). M. davidii is also a small myotodont species, but has the upper premolars crowded, the second being completely displaced lingually from toothrow and is now considered as belonging to the mystacinus morpho-group (see illustrations in Benda et al. 2012). Compared to the closest relatives of M. secundus sp. n. in phylogenetic analyses (Clade VIII in figure 3), M. pruinosus has a less elevated frontal part of skull and relatively flat braincase (Fig. 6 c), whereas the skull of M. yanbarensis (known from Okinawa, Japan) is characterized by a longer rostrum, more globose braincase (Fig. 6 d) and is larger (e.g., CBL over 14 mm,) than M. secundus sp. n. (CBL about 13 mm). Furthermore, the tibia is particularly long in M. secundus sp. n. (about 17 mm), unlike in related M. pruinosus from Japan (13 mm). The tail of M. secundus sp. n. is nearly as long as head and body length, whereas it is distinctly longer in M. yanbarensis.

Phylogenetic relationships. The complete (1140 bp) Cyt b gene of the holotype and paratypes of M. secundus sp. n. are all similar (with less than 1% K2P distance) and diverge by at least 10.5% K2P distance from their closest relative, M. yanbarensis (Fig. 3) and by at least 20% for any other sympatric Myotis from Taiwan (Table 5). In a more general phylogenetic context, M. secundus sp. n. (named Myotis sp. 2 in Ruedi et al. 2013) is part of the strongly supported Clade VIII within the Myotinae radiation, together with M. yanbarensis, M. pruinosus, and representatives of the M. montivagus species complex. It also differs notably from species of the mystacinus morpho-group that appear in Clade VI (Fig. 3 and Ruedi et al. 2013).

Natural history. M. secundus sp. n. is essentially a forest-dwelling species, but we observed breeding females also occupying small holes or chinks in caves. It is common both in the lowlands and higher mountains, suggesting that this species may have a relatively broad ecological niche. It was found in sympatry with S. latirostris in the higher elevations. Lactating females were observed from May to July, while males with enlarged testis were recorded from August to March.