Plestiodon finitimus, Okamoto & Hikida, 2012

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 : 9-14

Plestiodon finitimus sp. nov.

(Japanese name: Higashi-Nihon-Tokage)

( Figs. 7–8 ; 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 ; Bleeker, 1858, p. 205 (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 quinquelineatus: Hilgendorf, 1880, p. 113 ; Fritze, 1891, p. 239 (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); Elpajewsky & Sabanejew, 1906, p. 255

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); Nikolski, 1915, p. 508; Terentjev, 1923, p. 76; Pavlov, 1932, p. 8; Taylor, 1936, p. 276 (in part); Nakamura & Uéno, 1963, p. 106 (in part); Hikida, 1979a, p. 38 (in part); Hikida, 1993, p. 2 (in part); Hikida, 1996, p. 80 (in part); Hikida & Motokawa, 1999, p. 235 (in part); Motokawa & Hikida, 2003, p. 97 ("eastern group"); Schmitz et al., 2004 (in part)

Eumeces pekinensis: Stejneger, 1925, p. 51 (in part, Ussuri coast population)

Eumeces xanthi: Taylor, 1936, p. 245 (in part, Ussuri coast population)

Plestiodon japonicus: Okamoto et al., 2006, p. 419 (in part); Okamoto & Hikida, 2009, p. 183 (‘northeastern lineage’ and ‘central lineage’); Brandley et al., 2011 p. 7; Brandley et al., 2012 p. 166 (in part)

Holotype. KUZ R 65128, an adult male, collected in Ikegami , Ota Ward , Tokyo Metropolis, eastern Japan (site 11, Fig. 1 , N35°35', E139°42' [ WGS84 coordinate], 20 m alt.). Kyoto University Museum Zoological Collection ( KUZ). Collected on June 16, 2008 by Taku Okamoto.

Paratypes. All collected from the type locality by Taku Okamoto, KUZ R64911–14 collected on April 14, 2008 ; KUZ R65125–27 , 65129 , and 65130 collected on June 16, 2008 ; KUZ R66059–63 collected on April 9, 2009 .

Referred specimens. Sapporo City, Hokkaido (site 1): KUZ R 45145–46, 45151–54; Mt. Hakkoda, Aomori City, Aomori Pref. (site 2): KUZ R 30349–53, 30384, 30674–77, 35199–200, 35222–23, 35244–45, 35885–88, 53901–02, 53906–08, 53910–13, 53915–24, 53947; Isawa, Iwate Pref. (site 3): KUZ R 60145; Sendai, Miyagi Pref. (site 4): KUZ R 61220–21; Sekikawa, Niigata Pref. (site 5): KUZ R 64127; Matsunoyama, Niigata Pref. (site 6): KUZ R 64568; Katashina, Gumma Pref. (site 7): KUZ R 60804; Tsumagoi, Gumma Pref. (site 8): KUZ R 60393; Hase, Nagano Pref. (site 9): KUZ R 60296; Zenpukuji, Suginami Ward, Tokyo Metro. (site 10): KUZ R 64548–50, 63860, 63916, 64001–04; Yamato Village, Yamanashi Pref. (site 12): KUZ R 51139–44; Azumi Village, Nagano Pref. (site 13): KUZ R 39023–28; Rokugo, Shimada City, Shizuoka Pref. (a part of site 14): KUZ R 61872–75; Kanaya, Shimada City, Shizuoka Pref. (a part of site 14): KUZ R 61876–79; Toyozawa, Mt. Hatta, Toyozawa, Fukuroi City, Shizuoka Pref. (a part of site 14): KUZ R 61880–84; Horinouchi, Kikugawa City, Shizuoka Pref. (a part of site 14): KUZ R 61885–88; Arai Town (4) and Hamamatsu City (5), Shizuoka Pref. (site 15): KUZ R 61229–32 and KUZ R 61233–37, respectively; Kasahara Town, Gifu Pref. (site 16): KUZ R 35177, 36274, 36276–83; Gifu City, Gifu Pref. (site 17): KUZ R 61534–40, 63861–62, 63997–98, 64366–68, 64520–22; Fujihashi Village, Gifu Pref. (site 18): KUZ R 51936, 58293–97, 59600

Diagnosis. A moderate-sized Plestiodon (ca. 60–90 mm SVL for adults). This species, together with P. japonicus and P. latiscutatus , is distinguished from the congeners other than the P. latiscutatus species-group members by having synapomorphies of the group ( Hikida, 1993): fan-shaped upper secondary temporal with emarginated posterior margin overlapped by lower secondary temporal, a pair of keeled postanal scales, and a single postmental. They differ from P. elegans (Boulenger) in lacking an enlarged irregular scale patch on the postfemoral region, from P. stimpsonii (Thompson) in always having five instead of seven yellowish stripe patterns on the dorsal to lateral surface of juveniles and a lateral line passing the level of the ear opening instead above the ear opening, and from P. elegans , P. marginatus , and P. stimpsonii in usually having postnasal and vivid orange coloring on the ventral surface of the head (and sometimes trunk) of adult males in the breeding season (late March to May). This species differs from P. barbouri (van Denburgh) in having 24–29 MSRs, from the Izu Insular populations of P. latiscutatus in having a bifurcating dorsal yellowish stripe 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 supralabials ( Fig. 2A ). This species, except for the Mt. Hakkoda population (site 2 in Fig. 1 ), differs from P. japonicus in having a pair of prefrontals usually separated from each other by a frontal and frontonasal. The Mt. Hakkoda population differs from P. japonicus in having a larger number (26–29) of MSRs and one or two postlabial(s) in comparable frequencies ( Fig. 4A, B ).

Description of holotype. An adult male, SVL 63.5 mm, tail length 87.4 mm; axilla to groin length 37.1 mm; head 12.7 mm length (tip of snout to posterior end of interparietal), 11.6 mm width, 7.9 mm height; eye length 3.8 mm; snout to anterior corner of eye length 5.4 mm; posterior corner of eye to ear opening length 6.0 mm; snout to ear opening length 14.3 mm; ear opening height 1.4 mm; ear opening width 0.9 mm; left forelimb length 17.5 mm; left hindlimb length 25.6 mm.

Snout rounded; rostral partly visible from above, overlapping supranasal, nasal, and the first supralabial; a pair of supranasals smaller than prefrontals, the left one overlapping the right one, and overlapping frontonasal; frontonasal as large as prefrontals, overlapped by anterior loreals, and overlapping prefrontal and frontal; a pair of prefrontals as large as frontoparietals, separated from each other, overlapped by anterior and posterior loreals, overlapping first superciliary, first supraoculars, and frontal; frontal large, longer than distance from it to snout, wider than frontonasal, narrower posteriorly, overlapping first to third supraoculars along both sides, frontoparietals posteriorly, and partially fused with left frontoparietal; four supraoculars, anterior ones overlapping posterior ones, the first one overlapped by the first superciliary; a pair of frontoparietals as long as width, the left one overlapping the right one, with suture of one third of these length, overlapped by third and fourth supraoculars, and overlapping parietal and interparietal; interparietal similar length and three quarters width of frontal, narrower posteriorly, overlapping both parietals and two nuchals; parietals very large, twice as long and wide as frontoparietals, overlapped by fourth supraocular, upper and lower pretemporals, and overlapping upper secondary temporal and nuchal; a pair of nuchals, left one overlapping right one in anterior part, but overlapped by right one in middle to posterior part; nasal slightly smaller than the first supralabial, overlapping postnasal, supranasal, and the first supralabial; postnasal small, overlapping supranasal and anterior loreal, overlapped by first and second supralabials on left side (overlapped by the first supralabial only on right side); anterior loreal four times larger than postnasal in area, overlapped by supranasal and the second supralabial on left side (overlapped by the first and second supralabial on right side), and overlapping posterior loreal; posterior loreal similar height and twice width of anterior loreal, overlapping the first superciliary, preocular, and the first presubocular, overlapped by the second to third supralabial; six superciliaries on left side (seven on right side); two small pretemporals with similar sizes; the upper pretemporal overlapped by fourth supraocular, two postoculars and the last superciliary and overlapping the lower pretemporal; the lower pretemporal overlapped by the lower postocular and third postsubocular, overlapping primary temporal, upper secondary temporal; preocular small, overlapping small scales of eyelids; two presuboculars, the first one slightly smaller than the first superciliary, overlapped by third and fourth supralabials, the second one as large as the first, overlapped by the first presubocular and fourth supralabial, and overlapping fifth supralabial; two small postoculars; three postsuboculars, anterior ones overlapping posterior ones, the first and second ones overlapping the sixth supralabial, and the third one overlapped by the lower postocular; single primary temporal, as large as fourth supraocular, overlapped by second to third postsuboculars and sixth supralabial, and overlapping seventh supralabial and upper and lower secondary temporals; two secondary temporals, upper one slightly smaller than parietal and fan-shaped with emarginated posterior margin, overlapping nuchal, and two tertiary temporals, and lower secondary temporal with rectangular shape much smaller in height than the upper one, overlapped by the upper one in anterior margin but overlapping that in central to posterior part on left side (overlapping the upper one on right side), overlapping lower tertiary temporal and upper postlabial, and overlapped by seventh supralabial; two tertiary temporals, much smaller in length than secondary temporals, similar in sizes and shapes to uniform imbricate scales on trunk, the upper one overlapped by the lower one, and overlapping nuchal on left side (overlapped by nuchal on right side); seven supralabials, first to fourth similar in size and smaller than the others, fifth and sixth in increasing order in size, and seventh much larger than the others especially in length, anterior ones overlapping posterior ones, the fifth and sixth ones just under eye; two postlabials, the upper one overlapping the lower one and the lower tertiary temporal, and both overlapped by the seventh supralabial; head scales in temporal region on both sides (upper secondary temporal, tertiary temporal, parietal, and seventh supralabial) somewhat wounded; mental as wide as and half height of rostral, overlapping the first infralabial and postmental; single postmental with pentagonal shape and as large as mental, overlapped by the first and second infralabials, and overlapping the first chinshields; six infralabials, sixth narrower and longer than the others, anterior ones overlapping posterior ones; three pairs of chinshields with obliquely oriented rectangular shape, slightly smaller than postmental, the first one overlapped by second and third infralabials, right one overlapping left one, second one separated each other by a single row of small scales, overlapped by third and fourth infralabials, third ones separated each other by three small scales, overlapped by fourth and fifth infralabials and overlapping postgenial; a pair of postgenials, twice as large as the third chinshield, overlapped by the fifth and sixth infralabials; ear opening surrounded by small scales with four small ear lobules along anterior verge; forelimbs with distinct five fingers, third longest with 10 subdigitals on left side (11 subdigitals on right side), many footpads with various sizes; 52 pairs of paravertebral scales from posterior side of parietals to position of posterior margin of preanal, the paravertebral scales slightly wider than other trunk scales; ventral scales wider than lateral ones; 26 scale rows around mid-body; hindlimbs with distinct five fingers, fourth longest with 16 subdigitals, five large and many small footpads, no enlarged irregular scale patch in postfemoral region; a pair of enlarged preanals, left one overlap right one, both overlapped by smaller scales of outer sides; a pair of keeled postanal scales beside anal; subcaudal wider than the other scale rows around tail; 11 scale rows around tail at 10th subcaudal position.

In alcohol, dorsal surface of head to tail dark olive; dorsolateral surface of temporal to tail blackish brown; ventral surface of head whitish pink; ventral surface of trunk to tail light bluish gray.

DNA barcode. The nucleotide sequence of the 658 bp fragment of the mitochondrial COI gene (the standard barcode region) for the holotype was determined and deposited in the GenBank database (Accession No.: JN089935 ) . The nucleotide sequences of the 15 specimens from six localities, including nine paratypes, were additionally determined and deposited (Accession Nos.: JN089926 –34, JN089936 –41) .

Variation. Juveniles have the following color pattern: black background with five yellowish stripes on the dorsal and lateral surfaces of the head to the middle tail, pinkish or brownish light gray on the ventral surface of the head to middle tail, and a bright blue tail ( Fig. 9 ). The middorsal line begins on the snout, bifurcates to both sides, continues on the prefrontals, along both sides of the frontal, and on the frontoparietals, fuses at the posterior end of the interparietal, runs posteriorly on the median dorsal scale pairs, and ends around the middle tail. The dorsolateral line begins on the snout, continues on the first superciliary, along the outer side of the supraoculars, on the parietal, upper secondary temporal, the third and fourth trunk scale rows, and ends around the middle tail. The lateral line begins on the snout, continues on the anterior and posterior loreals, presuboculars, supralabials, and postlabials, through the ear opening, along the lateral side of the trunk, sometimes on the upper leg, and ends around the middle tail. Tail color in the basal region is somewhat faded and greenish and gradually changes into bright blue in the middle region. Adults have light brown on the dorsal surface, a black- or dark brown-colored band on the dorsolateral surface just between the lateral and dorsolateral stripe in juveniles, and pinkish or brownish light gray on the ventral surface. The juvenile color pattern is gradually lost and changes to the adult color pattern during ontogeny. The ontogenetic change occurs earlier in males than in females.

Mature males have relatively broader heads than the juveniles and females, as in most congeners ( Griffith et al. 2000). The ventral surface of the head to the trunk of mature males is bright orange-colored during the reproductive season (April to May in Tokyo).

There are two genetic lineages in this species: one from northeastern and one from central Japan, characterized by distinct mtDNA sequences and restriction fragment length polymorphism (digestion of PCR products by the restriction enzyme Hin f I) electrophoretic patterns of an internal transcribed spacer of the nuclear ribosomal gene (ITS-1). There is a wide area between the geographic ranges of the northeastern and the central Japan lineages, which is occupied by genetically intermediate populations with northeastern mtDNA and central ITS-1 ( Okamoto & Hikida, 2009).

The Mt. Hakkoda population (site 2, Fig. 1 ), which belongs genetically to the northeastern lineage, has prefrontals usually contacting each other ( Fig. 3B ), a larger number of MSRs (26–29, 26 and 28 occur at similar frequencies), and sometimes (approximately 40%) one postlabial ( Fig. 4A ). The distinct morphology of the Mt. Hakkoda population may not be shared by the other populations in northern Japan: most specimens from the northern part of Honshu (sites 3–9) exhibited A type PF and 26 or fewer MSRs (see Appendix 2). The populations of Zenpukuji, Suginami, Tokyo Metro. (site 10), and Kasahara, Gifu Pref. (site 16) tended to have a smaller number of MSRs (5/9 and 7/10 had 24 rows, respectively). The populations from Yamato, Yamanashi Pref. (site 12) frequently (4/6 and 3/6 for left and right sides, respectively) had large postnasals contacting the posterior loreal ( Fig. 2B ).

Large-sized adults were less frequent in the northeastern Japan populations (sites 1–14, Fig. 1 ) than in the central Japan populations (sites 16–18, Fig. 1 ). The percentages of specimens in the northeastern populations with SVL> 60 mm (N = 32), which were also> 70 mm and 75 mm, were 18.7% and 3.1%, respectively, compared with 44% and 20%, respectively, in the central Japan populations (N = 25).

Distribution. Central and northeastern parts of mainland Japan and several adjacent islets except the Izu Peninsula and the Izu Islands, and the coastal region of the Russian Far East (Primorsky and Khabarovsk). There is no record from Sakhalin. Except for the Russian Far East, the northernmost distribution is Hokkaido Island. The populations in Kunashiri Island in the southern Chishima (Kuril) Islands [formerly identified as Eumeces latiscutatus sensu Taylor (1936) ] may also belong to this species (the specimen examined by TH [MMSU NR 4704 of Moscow State University collection] had A type and B type PN on the left and right sides, respectively, intermediate PF, and 27 MSRs). The westernmost distribution is the southern Kii Peninsula and the eastern and northern side of Lake Biwa (northern side of Yasu River, Okamoto & Hikida 2009). Around the Izu Peninsula, the distribution is defined by the western side of the lower Fuji River, the northern side of Mt. Fuji, and the northern and eastern side of the Sakawa River ( Okamoto et al. 2006). This species seemed quite rare in the Tohoku District (the northern part of the largest main island around sites 3, 4, and 5, Fig. 1 ; Taku Okamoto, pers. obs.; also postulated by Stejneger, 1907, p. 199), except for Mt. Hakkoda (site 2), whereas the Mt. Hakkoda population seemed relatively abundant along the river near the hot springs (Tsutomu Hikida, pers. obs.).

Natural history. This species has a similar phenology to P. japonicus ( Hikida 1981) . It is active in the daytime with direct sunlight in the spring to autumn, and hibernates during the winter. Mature males with nuptial coloration appear in the spring (late March to May in Tokyo to central Japan), whereas mature females are secretive. Hatchlings appear in late July to early August, after the rainy season (middle June to middle July). Males and females of all ages are active in the summer to autumn (August to October).

Etymology. The Latin epithet finitimus means ‘adjacent’ or ‘neighboring’ and refers to the parapatric geographic range of this species with the two congeners P. latiscutatus and P. japonicus . The epithet also means ‘related to’ or ‘similar to’ and refers to the morphological similarity to P. latiscutatus and P. japonicus owing to their close kinship.

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.

FIGURE 7. Head scutellation of the holotype of P. finitimus sp. nov. (KUZ R65128). Dorsal (A), lateral (B), and ventral (C) views.

FIGURE 8. Dorsal view of the holotype of P. finitimus sp. nov. (KUZ R65128).

FIGURE 9. Typical coloration of P. finitimus juveniles (live, anesthetized). Upper: KUZ R60220, lower: KUZ R60221.