Plestiodon japonicus ( Peters, 1864 )

Okamoto, Taku & Hikida, Tsutomu, 2012, A new cryptic species allied to Plestiodon japonicus (Peters, 1864) (Squamata: Scincidae) from eastern Japan, and diagnoses of the new species and two parapatric congeners based on morphology and DNA barcode, Zootaxa 3436 (1), pp. 1-23 : 14-15

Plestiodon japonicus ( Peters, 1864)

(Japanese name: Nihon-Tokage)

( Table 1)

Scincus quinquelineatus: Temminck & Schlegel, 1838, p. 99 , p. 139 (in part)

Plestiodon quinquelineatus: Duméril & Bibron, 1839, p. 707 (in part)

Plestiodon quinquelineatum: Gray, 1845, p. 91 (in part); Bleeker, 1858, p. 205 (in part)

Eumeces (Plestiodon) quinquelineatus var. Japonicus: Peters, 1864, p. 57 (in part); von Martens, 1876, p. 376 (in part)

Eumeces (Plestiodon) japonicus: Böttger, 1878, p. 4 (in part)

Eumeces japonicus: Bocourt, 1879, p. 423 (in part); Goris & Maeda, 2004, p. 162 (in part)

Eumeces marginatus: Boulenger, 1887, p. 371 (in part); Okada, 1891, p. 70 (in part); Boettger, 1893, p. 111 (in part); Fritze, 1894, p. 860 (in part)

Eumeces quinquelineatus: Fritze, 1891, p. 239 (in part)

Eumeces latiscutatus latiscutatus: Stejneger, 1907, p. 195 (in part); van Denburgh, 1912, p. 213 (in part); Okada, 1939, p. 162 (in part)

Eumeces latiscutatus: Barbour, 1909, p. 63 (in part); Hatta, 1914, p. 31 (in part); Taylor, 1936, p. 276 (in part); Nakamura & Uéno, 1963, p. 106 (in part); Hikida, 1979a, p. 38 (in part); Hikida, 1981, p. 85; Hikida et al., 1992, p. 36 (in part); Hikida, 1993, p. 2; Kato et al., 1994 (in part); Hikida, 1996 (in part); Hikida & Motokawa, 1999, p. 235 (in part); Motokawa & Hikida, 2003, p. 97 (‘western group’); Schmitz et al., 2004 (in part)

Plestiodon japonicus: Okamoto et al., 2006, p. 419 (in part); Okamoto & Hikida, 2009 p. 183 (‘western lineage’); Brandley et al., 2012 p. 166 (in part)

Diagnosis. A moderate-sized Plestiodon (ca. 60–90 mm SVL for adults) similar to P. finitimus . This species differs from P. barbouri in having 24–28 MSRs, from insular populations of P. latiscutatus in having a bifurcating lateral white line pattern on juvenile heads, and from the Izu Peninsular population of P. latiscutatus in usually having a small postnasal and large anterior loreal contacting the supralabial ( Fig. 2A ). This species differs from P. finitimus , except for the Mt. Hakkoda population, in usually having prefrontals contacting each other, and from the Mt. Hakkoda population of P. finitimus in frequently having 26 MSRs, and in usually having two postlabials ( Fig. 4B ).

DNA barcode. The nucleotide sequence of the 658 bp fragment of the mitochondrial COI gene (the standard barcode region) for nine specimens from six localities including the type locality, was determined and deposited in the GenBank database (Accession Nos.: JN089947 –55) .

Variation. This species has a similar color pattern during ontogeny and sexual dimorphism, including breeding season coloration, to P. finitimus . There are large genetic variations in the allozyme ( Motokawa & Hikida 2003) and the mtDNA ( Okamoto & Hikida 2009). A small postnasal separated from the posterior loreal ( Fig. 2A ) is usual, while a large postnasal contacting the posterior loreal ( Fig. 2B ), and an absent postnasal are rare ( Fig. 2C ). The prefrontals usually contact each other, but are sometimes separated by the frontal and frontonasal ( Fig. 3A ), especially in the Kagoshima, Tanegashima Island, Kuchinoerabujima Island, and Iojima Island populations (site 34, 36, 37, and 38 of Fig. 1 ). The number of MSRs is usually 26, but can vary from 24 to 28. The Kagoshima population (site 34 of Fig. 1 ) has 26 and 28 MSRs with similar frequencies.

Distribution. Western Japan including Kyushu, Shikoku, western Honshu, and several adjacent islets. The easternmost distribution is the central to northwestern Kii Peninsula (northern Wakayama Pref., northern Nara Pref., and northwestern Mie Pref.), the southern side of the Yasu River on the eastern side of Lake Biwa, and the western side of Lake Biwa ( Okamoto & Hikida 2009). The westernmost and southernmost distributions are the Danjo Islands and Yakushima Island, respectively ( Motokawa & Hikida 2003). This species is not distributed in Tsushima and the Korean Peninsula. An artificially introduced population of this species is established on Hachijojima Island, part of the Izu Islands ( Kuriyama et al. 2009b).

Figures

FIGURE 1. Localities of the specimens examined in this study. Sites 1–18: Plestiodon finitimus; 19–24 and 39: P. latiscutatus; 25–38: P. japonicus; R1 and R2: Russian Far East specimens. The lines (a) and (b) represent boundaries between the geographic ranges of P. finitimus and P. japonicus, and P. finitimus and P. latiscutatus, respectively.

FIGURE 2. Observed major character states in arrangement of postnasal, supralabial, anterior loreal, and posterior loreal (PN) scales. p: postnasal; sl: supralabial; a: anterior loreal; po: posterior loreal.

FIGURE 3. Observed major character states in arrangement of prefrontal, frontonasal, and frontal (PF) scales. A few specimens exhibited an intermediate state between the A and B type. pf: prefrontal; fn: frontonasal; f: frontal.

FIGURE 4. Observed major character states of postlabial (PL) scales. sl: last supralabial; t: lower tertiary temporal; p: postlabial.