Research Article |
Corresponding author: Kôji Sasakawa ( ksasa@chiba-u.jp ) Academic editor: Terry Erwin
© 2016 Kôji Sasakawa.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Sasakawa K (2016) Two new species of the ground beetle subgenus Sadonebria Ledoux & Roux, 2005 (Coleoptera, Carabidae, Nebria) from Japan and first description of larvae of the subgenus. ZooKeys 578: 97-113. https://doi.org/10.3897/zookeys.578.7424
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Sadonebria Ledoux & Roux, 2005 is one of the more diverse subgenera of the genus Nebria Latreille, 1802 in East Asia, and its taxonomy remains unrevised at the subgeneric and specific levels. In this paper, two new species of this subgenus are described from Japan. Nebria quinquelobata sp. n. is described from Mt. Myôkô and is externally similar to Nebria saeviens Bates, 1883, to which specimens of this new species previously had been assigned. Nebria yatsugatakensis sp. n. is described from the Yatsugatake Mountains and is externally similar to locally adjacent species that had been recognized as Nebria sadona Bates, 1883 and were recently revealed as separate species. Both new species are distinguished by morphological (the shape of the endophallus) and morphometric (geometric morphometrics of the pronotum and aedeagus) features. For N. yatsugatakensis, the morphology of all larval instars is described based on specimens reared from eggs laid by collected adults. These results, together with previous studies of the species-level taxonomy of Sadonebria and larval morphology of other Nebria subgenera, suggest (i) the utility of geometric morphometrics in species-level taxonomy; (ii) the importance of larval secondary setae in the subgeneric taxonomy of the genus Nebria; and (iii) the presence of further cryptic species in Sadonebria.
Cryptic species, endophallus, geometric morphometrics, larval morphology, male genitalia, Nebria quinquelobata sp. n., Nebria sadona , Nebria yatsugatakensis sp. n., taxonomy
Sadonebria Ledoux & Roux, 2005 is an endemic East Asian subgenus of the genus Nebria Latreille, 1802 (Coleoptera, Carabidae). To date, 15 species-group taxa (13 species and two subspecies) have been described in this subgenus. Among the 15 taxa, N. chinensis Bates, 1872, which has developed hind wings, is widely distributed in China, Korea, and Japan (
The distribution of Nebria (Sadonebria) spp. in the Japanese Archipelago; N. chinensis Bates, which is distantly related to the remaining species, and samples that are not identified by genital morphology are not included [modified from
In this paper, two new species of Sadonebria are described from the area east of Kinki, Honshu, Japan. As with the recently described species, the new species are separated from known species based on the shape of the endophallus. Here, in addition to comparative morphology of this genital character, geometric morphometrics of external and genital characters are also performed. This morphometric technique can effectively evaluate subtle morphological differences, which are difficult to detect by traditional morphometrics, and is now widely used for the analysis of morphometric data (e.g.,
Information regarding comparisons of adults of related species was obtained from
To obtain larval specimens, adults of N. yatsugatakensis sp. n. were reared in plastic boxes (17.0 × 8.5 × 4.5 cm) following the technique described in
The examined specimens were deposited in the collections of the
Geometric morphometrics were performed for the dorsal view of the pronotum and the left lateral view of the aedeagus of male genitalia using the following materials: N. quinquelobata sp. n., 3♂1♀, N. saeviens, 5♂6♀; N. yatsugatakensis sp. n., 3♂6♀; and N. chichibuensis Sasakawa, 2010, 1♂2♀. The materials of species other than N. saeviens are type series of each species. Scaled digital images were obtained using a charge-coupled device camera attached to the microscope, after adjusting the tilt in the horizontal direction of materials. The pronotum was maintained with the anterior and posterior ends (landmarks 6 and 15 in Fig.
Positions of landmarks (numbers with asterisks) and semi-landmarks (numbers without asterisks) on (2) a pronotum in the dorsal view and (3) an aedeagus in the right lateral view. Landmarks indicated in (2) are as follows: (1*) anterior end along the median line; (6*) apex of anterior angle; (15*) apex of posterior angle; (17*) proximal end of posterior angle; and (19*) posterior end along the median line. Landmarks indicated in (3) are as follows: (1*) apical end of membranous portion; (3*) aedeagal apex; (17*) basal end of ventral side of cylindrical part; (18*) apex of the prominence between landmarks 17 and 19; (19*) basal end of ventral side; (20*) basal end of dorsal side; and (31*) basal end of membranous portion. Semi-landmarks were plotted along the curvature at regular intervals between landmarks.
For the pronotum, five landmarks and 14 semi-landmarks were identified (Fig.
To statistically evaluate shape differences, Procrustes ANOVA with 10,000 permutations was performed using the function procD.lm in the R package geomorph (
The two new species described here were distinguished from known species based on the shape of the endophallus. This result was complemented by that of geometric morphometrics, which is described later.
The two new species shared the following adult morphological character states. Habitus slender. Hind wings atrophied. Chaetotaxy as in other consubgeneric species (
Nebria saeviens (part):
Nebria (Orientonebria) saeviens (part):
Nebria (Sadonebria) saeviens (part):
Holotype: ♂ (
The specific name derives from the Latin adjectives quinque- (five of) and lobatus, -a, -um (with lobes) and refers to the ventral view of the male endophallus (Fig.
Left lateral view (a), left dorsolateral view (b), ventral view (c), and posterior view (d) of the endophallus of Nebria (Sadonebria) spp. 8 N. quinquelobata sp. n., holotype male 9 N. saeviens, male from type locality 10 N. yatsugatakensis sp. n., holotype male 11 N. chichibuensis, holotype male. go, gonopore; da, dorsoapical lobe; db, dorsobasal lobe; va, ventroapical lobe, la, lateroapical lobe; lb, laterobasal lobe.
Similar to N. saeviens (Fig.
External structures: Body length (including mandibles): ♂, 11.7–12.3 mm (mean ± SD: 12.0 ± 0.30 mm, n = 3); ♀, 13.1 mm (n = 1). Head with a reddish-brown patch between the eyes; pronotum reddish brown on the central part and dark brown at the lateral margins; head and other pronotal parts and elytra black; legs yellowish to light brown.
Male genitalia: Laterobasal lobes and lateroapical lobes both largely swollen and widely rounded, with the former slightly smaller than the latter; the dorsoapical lobe similar in size to the laterobasal lobe and bifurcated in a T shape at the apex; dorsobasal lobe distinct but smaller than the other lobes.
Nebria sadona (part):
Nebria (Orientonebria) sadona (part):
Nebria (Sadonebria) sadona (part):
Holotype: ♂ (FZUT), Tamagawa, Minoto, Chino-shi [the Yatsugatake Mountains], Nagano Prefecture, Japan (35°58'52.6"N, 138°18'29.4"E; ca. a.l.t. 1600 m), 4-5.ix.2010, K. Sasakawa leg. Paratypes (KS): 2♂6♀, same locality (2♀, 15-16.ix.2009, K. Sasakawa & H. Ikeda leg.; 2♂4♀, 4-5.ix.2010, K. Sasakawa leg). Larval specimens (KS) are not designated as type materials.
The specific name is derived from the Yatsugatake Mountains, the type locality of the new species.
Similar to locally adjacent species, such as N. chichibuensis Sasakawa, 2010 (Figs
External structures: Body length (including mandibles): ♂, 11.7–12.9 mm (mean ± SD: 12.2 ± 0.58 mm, n = 3); ♀, 12.8–13.9 mm (mean ± SD: 13.3 ± 0.41 mm, n = 6). Head without a reddish-brown patch between eyes; pronotum entirely black, but lateral margins dark brown in some specimens; legs dark brown, except for the femora, which are brownish black.
Male genitalia: Laterobasal lobes markedly swollen; laterapical lobes superficial; dorsoapical lobe large, similar in size to the laterobasal lobe, with the apex bifurcated in a Y shape; dorsobasal lobe distinct but smaller than the laterobasal and dorsoapical lobes.
In older instars, distinguished from congeneric species by numerous setae on the entire surface of thoracic nota and abdominal tergites (see Discussion).
Characters present in all instars: head capsule dark-brown to brownish black, with lighter ventral side; mouthpart appendages and legs brown to light-brown; urogomphi light- to dark-brown; other scletites on thorax and abdomen gray to brownish-gray; membranous parts grayish white. Most primary setae and pores present, but at least the following ones absent: FR8, FR9, LA4, PR7, ME2, TE4, TE6, TE9, EM1, FRf, PAn, COd, TEb, and PYe. Head capsule oval, widest at stemmata. Frontale U-shaped at base, with posterior end at the level of basal 1/3 of head capsule; nasale prominent, with three pairs of large projections; adnasale sloping posterolaterally. Parietale with six stemmata; cervical groove absent; coronal suture present. Antennae longer than mandible; antenomeres I and III subequal in length, longer than II and IV. Mandible slender and arcuate, with sharp apex; terebra without tooth-like processes; retinaculum as long as the width of the mandible at the level of MN1 and curved inward, with sharp apex. Maxilla with stipe as long as palpomeres III and IV combined; palpomere II and III subequal in length, shorter than IV, and longer than I; membranous notch absent. Labium with cordate prementum and elongated ligula; palpomere I longer than ligula but shorter than palpomere II. Thoracic nota and abdominal tergites transverse; notal carina of meso- and metanotum and abdominal tergal carina distinct. All legs with two unequal claws, with the anterior claw longer than the posterior one. Urogomphi slender, longer than head capsule.
Characters restricted to first-instar larvae: head width 1.16–1.22 mm (mean ± SD: 1.20 ± 0.02 mm, n = 5). Urogomphi 1.59–1.72 mm (mean ± SD: 1.66 ± 0.05 mm, n = 5). Secondary setae present on maxilla (9–11 for gMX), pronotum (one on central part, and one on posterior part), and abdominal epipleurite (one on central part). Head capsule with longitudinal, keel-like egg-bursters. Antennomere II almost cylindrical, subequal in length to IV. Maxillary palpomere III less than half the length of IV. Pronotum with indistinct notal carina. Urogomphi fused to tergite IX.
Characters restricted to older instars: Head width 1.50–1.52 mm (mean ± SD: 1.51 ± 0.01 mm, n = 4) in second instar; 1.80–1.89 mm (mean ± SD: 1.85 ± 0.04 mm, n = 5) in third instar. Urogomphi 2.08–2.27 mm (mean ± SD: 2.19 ± 0.08 mm, n = 4) in second instar; 2.51–2.94 mm (mean ± SD: 2.77 ± 0.16 mm, n = 5) in third instar. Secondary setae present on antennomere I (two on inner side), maxilla (14–19 for gMX, and two near MXb), labium (one behind LA3), frontale (absent or less than two near FRe and/or about three around FR1–3), and epimeron (absent or less than two); parietale, thoracic nota, abdominal tergites, epusterna, epipleurites, pleurites, sterna, pygidium, urogomphi, legs except claws with numerous secondary setae on entire surface. Antennomere II longer than IV, with the distal end being distinctly wider than the proximal end. Maxillary palpomere III more than half the length of IV. Pronotum with notal carina distinct. Urogomphi not fused to tergite IX.
For larvae reared at 5°C, the number of days (mean ± SD) of the first and second instars were 25.50 ± 2.25 (n = 16) and 42.50 ± 1.87 (n = 6), respectively. For larvae reared at 10°C, the durations of first and second instars were 15.29 ± 0.61 (n = 14) and 22.13 ± 2.30 (n = 8).
Relative warp analyses generated 27 and 11 scores for the pronotum and the aedeagus, respectively. To visually capture the results, scatter plots based on the first two scores were created (here referred to as RW1 and RW2). In the pronotum, RW1 accounted for 31.9% of the total variance and was mainly associated with the sinuation of the basal part of the lateral margin (landmarks 12–15). RW2 accounted for 20.0% of the total variance and was mainly associated with the sinuation of the lateral side of the posterior margin (landmarks 15–17) and relative size of the apical half. On the scatter plot, four species with overlapping areas were segregated (Fig.
First-instar N. yatsugatakensis sp. n. 12 Dorsal view 13 antenna (a dorsal view; b ventral view) 14 maxilla (a dorsal view b ventral view) 15 labium (a dorsal view b ventral view) 16 prothorax and mesonotum, dorsal view 17Ditto, right lateral view 18 tergites, dorsal view 19 urogomphi, dorsal view. ME, mesonotum; PR, prothorax; TE, first abdominal tergite. The homology of characters marked with an asterisk (*) is uncertain.
First-instar N. yatsugatakensis sp. n. 20 Head capsule, dorsal view 21 right foreleg, anterior view. CO, coxa; FE, femur; FR, frontale; MN, mandible; PA, parietale; TA, tarsus; TI, tibia; TR, trochanter. For the foreleg, the homology of characters marked with an asterisk (*) is uncertain, and characters with a hyphen (–) are present on the posterior side.
Third-instar N. yatsugatakensis sp. n. 22 Dorsal view 23 antenna (a dorsal view b ventral view) 24 maxilla (a dorsal view b ventral view) 25 labium (a dorsal view b ventral view) 26 prothorax and mesonotum, right lateral view 27 tergite, dorsal view 28 urogomphi, dorsal view. ME, mesonotum; PR, prothorax; TE, first abdominal tergite. The homology of characters marked with an asterisk (*) is uncertain.
Third-instar N. yatsugatakensis sp. n. 29 Head capsule, dorsal view 30 right foreleg, anterior view. CO, coxa; FE, femur; FR, frontale; MN, mandible; PA, parietale; TA, tarsus; TI, tibia; TR, trochanter. For the foreleg, the homology of characters marked with an asterisk (*) is uncertain, and characters with a hyphen (-) are present on the posterior side.
Scatter plot of RW1 and RW2 for the pronotum (A) and representations of extreme shape along each axis (B). Coordinates of each shape on the plot are presented in parentheses. Triangle- (△), circle- (○), square- (□), and diamond- (◇) marks denote N. quinquelobata sp. n., N. yatsugatakensis sp. n., N. chichibuensis, and N. saeviens, respectively. Black and white marks denote male and female, respectively. Broken lines represent connections along the margin of each species.
In the aedeagus, RW1 accounted for 48.8% of the total variance and was mainly associated with the relative size (length between landmarks 1 and 31) and the sinuation (curvature of landmarks 5–10) of the subapical portion. RW2 accounted for 30.0% of the total variance and was associated mainly with slenderness, particularly of the basal half. On the scatter plot, four species were clearly segregated and did not overlap. Results of Procrustes ANOVA revealed that the overall difference was significant (F3,7 = 2.586, Bonferroni-corrected p < 0.001). Post hoc tests indicated that N. quinquelobata and N. saeviens were significantly different (F3,4 = 1.043, Bonferroni-corrected p = 0.045), with N. yatsugatakensis being intermediate (vs. N. saeviens: F3,4 = 0.865, Bonferroni-corrected p = 0.101; vs. N. quinquelobata: F3,2 = 0.746, Bonferroni-corrected p = 0.256).
In Sadonebria, nine new species have recently been separated from known species based on differences in the shape of the endophallus (
The results of geometric morphometrics complement those of the comparative morphology of the male endophallus. For example, morphometric values for both the pronotum and aedeagus were clearly different between N. quinquelobata and N. saeviens, and these differences were statistically supported. Although the difference in the pronotum between N. yatsugatakensis and N. chichibuensis was not statistically supported, the two species were largely segregated on the scatter plot and only partially overlapped. In the analysis of the aedeagus, the two species are clearly segregated, and this difference was comparable to that between N. quinquelobata and N. saeviens, for which the morphometric difference was statistically supported. Some of the statistical insignificances in the results of geometric morphometrics would be attributed to the small sample size of some species. Future studies need to address this issue by re-analysis using additional materials. Importantly, the geometric morphometrics performed here are based on external and genital structures that had been virtually neglected in recent studies of Sadonebria. Nevertheless, these results discriminate among very similar species, with an accuracy close to that of comparative morphology of the male endophallus. Thus, geometric morphometrics can provide insights into future studies of Sadonebria taxonomy. For example, geographic variation in widely-distributed species can be examined by this morphometric technique.
In the genus Nebria, larvae of species from the following 10 subgenera have been described [subgeneric taxonomy follows
I thank H. Ikeda (Hirosaki University, Hirosaki, Japan) for his help in sample collection, Y. Nakatani, K. Yasuda and S. Yoshimatsu (