Silpha longicornis Portevin, 1926

Nishikawa, Masaaki, Ikeda, Hiroshi, Kubota, Kohei & Sota, Teiji, 2010, Taxonomic redefinition and natural history of the endemic silphid beetle Silpha longicornis (Coleoptera: Silphidae) of Japan, with an analysis of its geographic variation, Zootaxa 2648, pp. 1-31 : 5-14

Silpha longicornis Portevin, 1926

( Figs. 1–14, 16 )

Phosphuga japonica Portevin, 1920: 309 ; type locality: Chiuzinji [= Chûzenji, Nikko, Tochigi Pref., central Honshu, Japan].

Silpha longicornis Portevin, 1926: 69 (nom. nov. for Phosphuga japonica Portevin, 1920 (non Silpha japonica Motschulsky, 1862 ))

Silpha (Silpha) yamatona Kôno, 1929: 158 ; type locality: Sanjodake, Yamato [= Nara Pref.], syn. nov.

Silpha imitator Shibata, 1969: 49 ; type locality: Mt. Ohmine, Yamato, Honshu. syn. nov.

Type specimens examined. Silpha longicornis Portevin. Lectotype (here designated): female in “COLLECTION GENERALE / SILPHIDAE ”, MNHN, bearing the following labels ( Fig. 2 ): “ Japon, Chû- / - zenji, 23-7-10 / Edme Gallois”, “MUSEUM PARIS / NIPPON MOYEN / E. GALLOIS 1912”, “ TYPE ”, “ Silpha / longicornis / Portevin, 1926 / Ψ / Jan Rûžička det. 2002”, “ LECTOTYPE / Silpha / longicornis / Portevin, 1926 / Ψ / Design. M. Nishikawa, 2008 ” (right antennal segments V–XI and left middle leg are missing). Paralectotype: female in “COLLECTION GENERALE / SILPHIDAE ”, MNHN, bearing labels with the same inscriptions as the lectotype and an additional label “ PARALECTOTYPE / Silpha / longicornis / Portevin, 1926 / Ψ / Design. M. Nishikawa, 2008 ” (the basal portion of the left elytron is slightly deformed).

Silpha yamatona Kôno. Holotype: male (listed as female in original description) in Kôno collection, HUM, bearing the following labels ( Fig. 4 ): “Sanjodake, / Yamato, / 9–VIII 1913 / T. Isshiki.”, “ Silpha / yamatona / Kôno / Type ”.

Silpha imitator Shibata. Holotype: male in Shibata collection, KCMI, bearing the following labels ( Fig. 6 ): “Mt. OHMINE / YAMATO / 27.VI.1960 / M. Yoshikawa”, “ Holotype ”, “ Silpha / imitator / SHIBATA / sp. nov. ď”, “a”. Paratypes: Ψ, “Dorogawa–Hôriki-tôge”, “DOROGAWA / YAMATO / 13.VIII. [print] 19 [handwritten] 58 / [print] T. Shibata”, [red rectangular label; print] “ Paratype ”, [orange rectangular label; print] “ Silpha / imitator / SHIBATA Ψ / sp. nov.” ( KCMI); ď, [white rectangular label; print] “MT. OHMINE / YAMATO / 1.VI.1961 / N. OHTANI”, [orange rectangular label; print] “ Silpha / imitator / SHIBATA / sp. nov. ď”, [red rectangular label; print] “ Paratype ” ( NSMT); Ψ, [white rectangular label; print] “Inamuragatake / Nara Japan / [handwritten] 14.VIII. [print] 19 [handwritten] 60 / I. Hiura leg.”, [red rectangular label; print] “ Paratype ”, [orange rectangular label; print] “ Silpha / imitator / SHIBATA Ψ / sp. nov.”, [light-blue rectangular label; print] “Osaka Mus. N.H. / Jap. Insect Coll. / No. [handwritten] 21377”; Ψ, [white rectangular label; print] “Kawai, Tenkawa / Nara, Japan / [handwritten] 21.VII. [print] 195 [handwritten] 6”, [white rectangular label; print] “Osaka Munic. Mus. / Nat. Hist. / Leg. M. Hori”, [red rectangular label; print] “ Paratype ”, [orange rectangular label; print] “ Silpha / imitator / SHIBATA Ψ / sp. nov.”, [light-blue rectangular label; print] “Osaka Mus. N.H. / Jap. Insect Coll. / No. [handwritten] 21376”; Ψ, [white rectangular label; print] “Mt. Inamura / Nara. Pref. / [handwritten] 22.VII. [print] 19 [handwritten] 61 / [print] Coll. Mitsuo Goto”, [red rectangular label; print] “ Paratype / Silpha imitator / Shibata”, [orange rectangular label; print] “ Silpha / imitator / SHIBATA Ψ / sp. nov.” (all in OMNH).

Geographic Distribution. Silpha longicornis is endemic to Japan and occurs in 17 mountain ranges of Honshu and Sado Island ( Fig. 18 ). This species is widespread in the mountainous areas in the northeastern Kii Mountains, but a gap exists between the Kii Mountains and Ryohaku Mountains in south–central Honshu. In the Kii Mountains, this species occurs in the central massifs, such as Daikô and Ômine, but not west of the Totsu-kawa River (Harusawa, pers. comm.).

The highest locality where this species has been found is at 2,300 m on Mt. Kiso-komagatake, and the lowest site is at 159 m altitude in Onoso, Yamagata Pref. ( Fig. 19 ). The mean altitude of the vertical range was 1,404 ± 474 (SD) m. The vertical limit was approximately 500 m above the border between evergreen coniferous and deciduous broad-leaved forests, and 500–700 m below the forest limit. Thus, this species inhabits cool −temperate and subalpine −coniferous forests.

Only three fossil specimens of this species have been found to date ( Fig. 18 ): in the Early Pleistocene Uonuma Formation (Higashikubiki Hills, Niigata Pref.), at the Late Pleistocene Taruguchi-iseki archaeological site (Asahi-mura, Niigata Pref.), and in the Late Pleistocene Nojiri-ko Formation (Ikejiri-gawa Hollow near Lake Nojiri-ko, Nagano Pref.; Hayashi 2002). The oldest of the three indicates that this species has existed for at least 1.2 to 0.9 million years ( Hayashi 2001).

Life History. Based on the field studies by Kamimura et al. (1964) and Martin (1989), a breeding observation (Ikeda, unpublished data), and previous predictions ( Kusakari 1993; Hosoda 1999), this species is thought to have a univoltine life cycle. It overwinters as an adult, and these adults are active from late spring and probably reproduce in early summer. Larvae appear from mid- to late summer and newly emerged adults occur in early autumn, so the pupal stage may occupy the interval from summer to early autumn.

Due to brachyptery and the absence of flight muscles, the principal microhabitat of S. longicornis is the ground surface ( Ikeda et al. 2007, 2008). During the active season, adults and larvae can be collected easily using pitfall traps set in small glades and at edges of forests or mountain roads. However, adults were attracted to carrion traps bound to branches about 1.5 m above the ground (Nishikawa, unpublished), indicating that adults are capable of climbing trees. From late autumn to late spring, hibernating adults are often found inside decaying trees and under stones. An aggregation of larvae of different sizes was found under a stone on the forest floor (Nishikawa, unpublished). This habit may be related to pupation.

This species was previously believed to feed on carrion and fungi, based on the observed attraction to carrion and predation marks on fungi ( Hirano 1985). However, Ikeda et al. (2007, 2008) used stable isotope analysis to demonstrate that this species is carnivorous, feeding mainly on earthworms.

Geographic variation in morphology. Five morphological dimensions (BL, PW, PL, EW, and EL) were integrated into the first principal component axis (PC1) with the highest contribution to the total variance in PCA (89.9%). PC1 was positively correlated with all five body dimensions. Multiple regression analysis showed that PC1 was larger in females than males (df = 1, F = 24.5, P <0.001) and positively regressed with AMT (df = 1, F = 63.8, P <0.001; Fig. 20 , see Table 3 for climatic data at each site). Thus, larger body sizes are exhibited in warmer localities. This pattern follows the converse of Bergmann’s rule ( Park 1949), as has been recognized in some insect groups (e. g., Masaki 1966; Sota et al. 2000), and could be caused by the decrease in the length of the season suitable for growth and activity with increasing latitude and altitude ( Šustek 1983; Hosoda 1999).

Elytral color variation in this species also showed a cline along the geographic gradients of temperature ( AMT; P <0.0001) and precipitation ( AMP; P <0.0001; Table 4 ). Darker elytral color was exhibited in warmer and wetter localities, and lighter elytral color in colder and drier localities. This geographic pattern in color variation follows Gloger’s rule ( Gloger 1883). In other silphid beetles, Šustek (1983) found that color variation in S. carinata was correlated with altitude and the accumulated temperature of a given locality, and concluded that color variation is influenced by climate. However, he did not examine the effect of humidity and did not refer to Gloger’s rule. In S. longicornis , the localities dominated by dark specimens are widespread across the distributional range, whereas the localities dominated by light specimens are sporadic and restricted mostly to the mountainous areas of central Honshu (see Appendix 3 for the proportions at each site).

Elytral microsculpture and punctation also varied along climatic gradients. The proportion of specimens showing punctate microsculpture increased significantly with increasing temperature ( AMT; P <0.001) and precipitation ( AMP; P <0.0001), and it was higher among females than males (P <0.0001). The smooth form was dominant in the mountainous areas of east–central Honshu (see Appendix 3 for the proportions at each site).

Locality Site No Latitude Longitude AMT AMP

Ôu Mountains

Osorezan 1 41.2732 141.1040 5.4 1838

Hakkoda/Towada 1 40.5688 140.7245 7.5 1379 2 40.5213 140.7755 7.6 1639 3 40.3890 140.7927 6.9 1738

Ninohe 1 40.0692 141.1050 5.8 1345

Iwatesan/Hachimantai 1 39.8368 141.0263 5.7 1912 2 39.8037 140.7925 5.7 2524

Mahiru 1 39.0032 140.8408 8.4 2068 2 38.9737 140.7673 5.3 2290

Zaô 1 38.4013 140.7077 7.7 1755 ......continued on the next page Locality Site No Latitude Longitude AMT AMP 2 38.2872 140.7858 11.0 1341 3 38.2363 140.4733 6.8 1375

Bandai 1 37.8372 140.3372 9.8 1437 2 37.7760 140.2213 6.9 1832 3 37.7732 140.1185 6.4 1762 4 37.7515 140.1412 1.5 1863 5 37.6588 140.2673 5.2 1986 6 37.6193 140.2860 3.7 1891 7 37.3918 140.1863 7.8 1458

Nasu 1 37.1208 139.9687 3.5 1768 2 37.1060 139.9228 6.1 1680

Shirakami Mountains 1 40.6522 140.2918 2.7 1692 2 39.7245 140.3233 9.4 2346

Kitakami Hills 1 39.8425 141.5057 5.3 1267 2 39.7025 141.7708 5.7 1331 3 39.6583 141.7595 8.3 1247 4 39.5672 141.3520 6.4 1337 5 39.5548 141.4865 1.4 1636 6 39.5338 141.4080 7.3 1443 7 39.1743 141.3917 7.2 1336

Dewa Mountains

Taihei 1 39.8030 140.2598 8.8 2508 2 39.8000 140.2702 8.3 2533

Hinotodake 1 39.1058 139.9667 8.1 3070 2 39.0878 139.9005 11.5 2653

Echigo Mountains

Asahi 1 38.2563 139.9200 2.7 2863 2 38.1750 139.9762 4.9 2582

Iide 1 37.9220 139.6022 5.0 3034 2 37.8893 139.6238 2.3 3235 3 37.8882 139.6005 4.4 3177 4 37.8413 139.6753 1.2 2989

Mikuni 1 36.9845 139.3425 5.5 1479 2 36.9228 139.3095 2.9 1612 3 36.8873 139.1930 3.3 1715 4 36.8702 138.7682 8.5 2036 5 36.8175 138.9432 5.8 1722 6 36.8063 139.1848 5.3 1381 7 36.7550 138.8238 7.5 1819 8 36.7518 138.8248 7.5 1819 9 36.6877 138.7710 9.4 1592 ......continued on the next page Locality Site No Latitude Longitude AMT AMP 10 36.5362 139.1755 5.3 1647 11 36.4035 138.6677 7.4 1537 12 35.4030 138.9093 8.2 2214

Taishaku 1 37.0062 139.4363 4.6 1510 2 36.9732 139.8693 8.8 1802 3 36.9687 139.7512 7.3 1453 4 36.9528 139.7578 7.4 1561 5 36.9173 139.7380 5.9 1661 6 36.8667 139.3875 4.2 1560 7 36.8393 139.3592 2.2 1582 8 36.8338 139.3415 3.6 1578 9 36.8228 139.3672 2.8 1622 10 36.8205 139.4342 3.1 1782 11 36.8182 139.3903 1.7 1620 12 36.8097 139.4515 3.2 1790 13 36.8067 139.4042 3.0 1663 14 36.7840 139.5008 3.5 2026 15 36.7382 139.4890 6.5 2056

Shirane/Shiga 1 36.6838 138.4905 3.5 1641 2 36.6760 138.4860 3.5 1641

Asama 1 36.6058 138.6380 9.1 1716 2 36.4407 138.4175 4.5 1296 3 36.4400 138.4178 4.5 1279 4 36.4023 138.5685 5.6 1537 5 36.3870 138.6087 7.4 1461 6 36.3857 138.6042 7.1 1493

Ôsado Mountains 1 38.1370 138.3872 8.5 2295 2 38.1035 138.3543 7.8 2220 3 38.1022 138.3432 7.8 2220 4 38.0753 138.3263 8.5 2026

Chikuma Mountains

Chikuma 1 36.9043 138.1422 7.0 2325 2 36.9037 138.1675 8.6 2308 3 36.8752 138.0528 5.6 2303 4 36.8670 138.0198 5.1 2247

Yatsu-ga-take 1 36.2577 138.0853 5.3 1310 2 36.2203 138.1097 3.4 1368 3 36.1365 138.0373 5.9 1346 4 36.1192 138.2877 3.8 1460 5 36.1075 138.3182 2.6 1490 6 36.0553 138.3410 2.4 1576 ......continued on the next page Locality Site No Latitude Longitude AMT AMP 7 36.0537 138.3220 2.9 1586 8 36.0500 138.3082 4.3 1581 9 36.0390 138.3927 6.0 1541 10 36.0350 138.3238 3.6 1576 11 36.0333 138.3060 4.6 1554 12 36.0095 137.2187 7.3 2340 13 35.9755 138.3232 4.7 1550

Kantô Mountains 1 36.1018 138.6368 6.5 1183 2 36.0333 138.6043 3.5 1457 3 36.0197 138.5843 6.5 1444 4 35.9022 138.9518 7.3 1559 5 35.8858 138.9503 5.9 1612 6 35.8758 138.6023 3.4 1440 7 35.8705 138.6577 1.5 1517 8 35.8587 138.9872 5.6 1621 9 35.8578 138.9403 5.8 1648 10 35.8365 138.6407 5.0 1396 11 35.8247 138.5595 6.0 1208 12 35.8002 138.5740 9.2 1189 13 35.7930 138.6503 6.8 1248 14 35.7722 138.8015 6.5 1472 15 35.7257 138.8260 6.9 1492

Misaka Mountains 1 35.5428 138.8055 5.8 1618

Tanzawa Mountains 1 35.5065 139.0677 7.1 1907 2 35.4763 139.1722 8.9 2122 3 35.4740 139.1017 7.1 2093 4 35.4712 139.1575 6.8 2072

Fuji Volcanoes 1 35.8900 138.1725 4.5 1460 2 35.4075 138.8875 8.8 2213 3 35.3883 138.8583 8.3 2360 4 35.3593 138.8013 6.9 2879 5 35.3208 138.7925 7.8 2943 6 35.2537 138.7847 9.8 2923 7 35.2428 138.8507 11.8 2992

Hida Mountains 1 36.5547 137.6533 4.4 2652 2 36.4013 137.7382 4.3 2179 3 36.2582 137.6870 4.7 2582 4 36.2413 137.6222 4.8 2784 5 36.1898 137.5835 4.0 2445 6 36.1858 137.7747 8.9 2103 7 36.1833 137.7765 8.9 2103 ......continued on the next page Locality Site No Latitude Longitude AMT AMP 8 35.9093 137.5415 6.2 2805 9 35.8667 137.5175 3.6 3356 10 35.8577 137.5253 4.4 3232 Kiso Mountains 1 35.7717 137.8193 0.6 2992 2 35.7695 137.8222 3.2 2942 3 35.4698 137.6258 5.9 2565 Akaishi Mountains 1 35.6837 138.3748 6.5 1573 2 35.4337 138.0237 4.6 1967 3 35.3172 138.3545 7.4 3034 4 35.1243 138.0388 7.9 2838 Ryohaku Mountains 1 36.1405 136.7258 3.6 3512 2 35.8248 136.4853 8.1 2817 3 35.7745 136.4055 8.1 2669

Kii Mountains

Daikô 1 34.3598 136.0875 7.1 2484 2 34.3570 136.0598 8.0 2376 Ômine 1 34.2545 135.9377 6.1 2269 2 34.2515 135.9378 6.0 2371 3 34.2513 135.9172 7.1 2238 4 34.2430 135.9183 7.1 2238 5 34.2378 135.8540 11.1 1982 6 34.2342 135.8552 10.4 2028 7 34.1745 135.9055 4.8 2758 8 34.1745 135.9050 4.8 2758 9 34.1745 135.9045 4.8 2758 10 34.1742 135.9238 6.8 2785 Hôriki-tôge 1 34.2548 135.9037 7.8 2142 Mt. Shaka-ga-take 1 34.0932 135.8833 7.4 2840 Dark Punctate Flat

Figures

FIGURE 18. Geographic distribution of S. longicornis Portevin based on the examined specimens (Appendix 1) and mountain ranges. Contour interval 1,000 feet. 1 — Ôu Mountains; 2 — Shirakami Mountains; 3 — Kitakami Hills; 4 — Dewa Mountains; 5 — Echigo Mountains; 6 — Ôsado Mountains; 7 — Chikuma Mountains; 8 — Kantô Mountains; 9 — Misaka Mountains; 10 — Tanzawa Mountains; 11 — Fuji Volcanoes; 12 — Hida Mountains; 13 — Kiso Mountains; 14 — Akaishi Mountains; 15 — Hida Hills; 16 — Ryohaku Mountains; 17 — Kii Mountains. Fossil sites (▲) are also shown.

FIGURE 19. Vertical distribution of Silpha longicornis Portevin based on the examined specimens (Appendix 1) and climatic vegetation zones. Solid line shows the maximum altitude along the transect. a—forest limit; b—border between evergreen coniferous and deciduous broad-leaved forests; c—hypothetical forest limit during the Last Glacial Maximum; d—hypothetical border between coniferous and broad-leaved forest during the Last Glacial Maximum. Modified from Nogami (2001: Fig. 4.2.1).

FIGURE 20. Relationship between AMT and PC 1. Females are indicated by open circles and the dashed line, and males are indicated by solid circles and the solid line.

FIGURES 1 – 16. Habitus of type specimens and labels (1 – 7): 1 — Silpha longicornis Portevin, lectotype, Ψ, dorsal view; 2 — same, labels; 3 — Silpha yamatona Kôno, holotype, ♂, dorsal view (photo by S. Shimano); 4 — same, labels (photo by S. Shimano); 5 — Silpha imitator Shibata, holotype, ♂, dorsal view; 6 — same, labels; 7 — same, aedeagus in ventral view. Details of Silpha longicornis Portevin, showing variation of elytron color (8 – 9), and sculpture (10 – 13): 8 — black specimen from Mt. Kurikoma, Iwate Pref.; 9 — reddish-brown specimen from Mt. Kasa-ga-take, Nagano Pref. (with aberration of elytral costae); 10 — rugose intervals; 11 — flat intervals; 12 — punctate microsculpture; 13 — smooth microsculpture. Apex of male metatibia, showing terminal projection (14). Prothorax of larvae of Silpha perforata Gebler (15, from Moheji near Hakodate, S. W. Hokkaido) and Silpha longicornis Portevin (16, from Jikkoku-tôge, Nagano Pref.).