Pterostichus (Petrophilus) eximius : Morawitz 1862

Pterostichus (Petrophilus) eximius Morawitz, 1862

Figs. 1, 2

Pterostichus (Steropus) eximius: Morawitz (1862): 212 (original description), type locality: “Zagan-olui und Tschindansk am Onon” [Transbaikalia, East Siberia].

Pterostichus (Euryperis) eximius: Jedlička (1962): 258; Lafer et al. (1997): 16.

Pterostichus (Steropus) sachalinensis: Kirschenhofer (1985): 222 (original description), type locality: “Süd-Sachalin, Umgeb. Nowoalexandrowsk, Bergwald (Tschechow-Berg)” [Mt. Chekhov, southern Sakhalin].

Pterostichus (Petrophilus) eximius: Kryzhanovskij et al. (1995): 107; Bousquet (2003): 505; Bousquet (2017): 731; Yoshimatsu et al. (2018): 96.

Pterostichus (Petrophilus) sachalinensis: Kryzhanovskij et al. (1995): 107; Berlov & Berlov (1997d): 38; Bousquet (2003): 505 (synonym of eximius); Bousquet (2017): 731 (synonym of eximius)

Materials examined. Pterostichus eximius eximius, 11♂ 6♀ (5♂ 2♀, Balyaga, Transbaikalia, vii.1991, Sokolov leg. in OB coll.; 6♂ 4♀, Chara, Chita Region /= Transbaikalia, 5.vi.1985, E. Berlov leg. in OB coll.); P. eximius sachalinensis, 10♂ 4♀, Mt. Chekhov, Sakhalin (10♂ 3♀, 14.vi.1990, E. Berlov leg. in OB coll.; 1♀, 30.vii.2005, T. Sota leg. in KS coll.); P. eximius rishiridakensis, 2♂ 10♀, see subspecific section.

Other consubgeneric species examined. Pterostichus montanus (Motschulsky), 2♂, Mt. Khulugaisha near Mondy, Tunkinskie goltsy Mts. ridge, Buryatia, 2300 m, 1-4.vii.1998, E. Berlov leg. in OB coll.; P. sutschanensis Jedlička, 3♂ (1♂, Lazovsky Pass, Primorsky Region, 4.viii.2005, T. Sota leg. in KS coll.; 2♂, Sichote-Alinsky state nature reserve, Primorsky Region, 18.vi.1998, Yundukov leg. in OB coll.). The following species were investigated through Sasakawa & Kubota (2005, 2006) and Sun et al. (2018): P. coracinus (Newman), P. findeli (Dejean), P. foveolatus (Duftschmid), P. habui Jedlička, P. jungens (Tschitschérine), P. lachrymosus (Newman), P. maichensis Lafer, P. maryseae Sun & Shi, P. melanarius (Illiger), P. robustistylis Sasakawa, P. silvestris Sun & Shi, P. stygicus (Say), P. thunbergi Morawitz, P. tuberifer Sasakawa, and P. uralensis (Motschulsky).

Notes. Pterostichus eximius was originally described based on specimens from Transbaikalia and is currently treated as a monotypic species without any geographical variants that are distinguished taxonomically. This monotypic status is based on work by Lafer et al. (1997), who examined type specimens and the original descriptions of some taxa, and synonymized them with P. eximius. However, they did not examine the endophallus of the male genitalia, a character that is important in the taxonomy of Carabidae.

Our comparative study of endophallic and aedeagal structures revealed that populations from the Rishiri-tô and Sakhalin islands are both distinguished from the nominotypical population from Transbaikalia. With regard to the endophalli, two morphological differences were found among specimens from the three localities. The first is sub-lobe rv-2 of the right ventral lobe, which is rudimentary in Transbaikalian specimens but distinctly developed in Rishiri-tô and Sakhalin specimens (Fig. 1, red arrows). The second is a swelling adjoining lobe ll (Fig. 1, green arrows), which is larger in Sakhalin specimens than in Transbaikalian and Rishiri-tô specimens. With regard to the aedeagus, differences were found in the shape of the subapical part among specimens. The dorsal contour of the lateral sides is straight in Rishiri-tô specimens, while in the Transbaikalian and Sakhalin specimens the dorsal contour is bent at an obtuse angle in the subapical part, and protrudes dorsally (Fig. 1, blue arrows). Thus, specimens from the three localities can be distinguished according to combinations of these endophallic and aedeagal characters. Based on this result, the three populations should now be regarded as separate subspecies. In this taxonomic system, the Sakhalin population is reinstated as a subspecies: P. eximius sachalinensis stat. nov. No scientific name was available for the Rishiri-tô population, so it is described as a new subspecies below.