Parorthomus socotranus, Gueorguiev, Borislav, Wrase, David W. & Farkac, Jan, 2014

Gueorguiev, Borislav, Wrase, David W. & Farkac, Jan, 2014, Revision of the East Mediterranean Orthomus (Coleoptera, Carabidae, Pterostichini), with description of Parorthomus gen. n. socotranus sp. n. from Socotra Island and key to the Old World genera of subtribe Euchroina, ZooKeys 427, pp. 21-57 : 40-48

Taxon classification Animalia Coleoptera Carabidae

Parorthomus socotranus sp. n. Figs 18-24, 28, Table 1

Orthomus sp.: Wranik 2003: 442, plate 170, Fig. f.

Type material.

Holotype ♂, "Yemen, Socotra Isl., Fimihin, GPS 12.474N, 54.015E, 530 m, x.2000, leg. V. Bejček & K. Št’astný” (DWBG) / "HOLOTYPE Parorthomus socotranus sp. n. Guéorguiev, Wrase & Farkač des. 2014" [black print on red label, black framed]. Paratypes 24 ♂♂, 29 ♀♀, labelled as follow: 4 ♂♂, 4 ♀♀, with the same data as the holotype (DWBG, JFPC, JSAG, NMNHS); 6 ♂♂, 10 ♀♀, "Soqotra-Archipel: Soqotra Hoq, Küstenebene bis Höhleneing., Kalk mit einigen Granitfelsen, dichte Veg., 50-320 m 12°36'N, 54°21'E, 5.-6.2.1999 leg.: H. Pohl, SOQ 08" (BMNH, DWBG, HLMD, MPHG); 3 ♀♀, "YEMEN: Socotra Isl. Haghier, 4.-8.X.2000 lgt. V. Bejček & K. Št’astný” (JFPC); 2 ♂♂, 1 ♀, "Yemen, Soqotra-Archipel, Soqotra, Wadi Danegan, Barberfallen, 90 m 12°36'59"N, 54°03'48"E, 28.-30.10.2000 leg.: T. VAN HARTEN & H. POHL SOQ 2000/02a" (HDLM); 2 ♂♂, "Yemen, Soqotra-Archipel, Soqotra, Homhil, Quelle mit Ficus, Licht 12°34'13"N, 54°18'32"E /leg. H. Pohl, 29.10.2000/SOQ 2000/13" (HDLM, MPHG); 1 ♂, "Yemen, Soqotra-Archipel, Soqotra, Wadi Danegan, 90 m 12°36'59"N, 54°03'48"E, 30.10.2000 leg.: T. VAN HARTEN" "SOQ 2000/02" (HDLM); 3 ♂♂, 1 ♀, "Yemen, Soqotra Is.; 28.-29.ix.2003 HOMHIL protected area N 12°34'27" E 54°18'32" 364 m [GPS]; Jan Farkač lgt." / "YEMEN - SOQOTRA 2003 Expedition; Jan Farkač, Petr Kabátek & David Král” (JFPC, NMNHS); 1 ♂, 1 ♀, "Yemen, Socotra Is., WADI AYHAFT, 24.-26.xi.2003, 12°36'38 ’’ N, 53°58'49 ’’ E, 190 m, [GPS], leg. P. Kabátek” / "YEMEN - SOQOTRA 2003 Expedition; Jan Farkač, Petr Kabátek & David Král” (DWBG); 1 ♂, 1 ♀, "Yemen, Soqotra Is., 2.xii.2003, Al Haghier mts. W slopes, skant area 12°35'52"N, 54°00'01"E 1240 m [GPS], D. Král leg." / "YEMEN - SOQOTRA 2003 Expedition; Jan Farkač, Petr Kabátek & David Král” (NMPC, RFBN); 1 ♂, "Yemen, Soqotra Is., QAAREH (waterfall), Noged plain, 5.-6.xii.2003, 12°20'10"N, 53°27'56"E, 57 m [GPS], leg. P. Kabátek” / "YEMEN - SOQOTRA 2003 Expedition; Jan Farkač, Petr Kabátek & David Král” (DWBG); 1 ♀, "Yemen, Soqotra Is., 6.-7.xii.2003 Noged plain: WADI IREEH N12°23'11", 53°59'47"E, 96 m [GPS]; Jan Farkač lgt." / "YEMEN - SOQOTRA 2003 Expedition; Jan Farkač, Petr Kabátek & David Král” (DWBG); 2 ♀♀, "Yemen: Socotra Isl., Wadi Ayhaft, lat. +1395751.449, lon +824616.2897, 27-30.10.2007, pitfall traps, F. Pella leg." (MBAP); 1 ♀, "YEMEN: Socotra Island E 410 m, 3. ii. 2010 N12°29'41", E 54°09'30" L. Purchart & J. Vybíral lgt." (NMPC); 1 ♀, "YEMEN: Socotra Island E Homhil area, 410-510 m, 12°34'25"N, 54°18'53"E 9-10. ii. 2010 L. Purchart & J. Vybíral lgt." (NMPC); 1 ♂, "YEMEN: Socotra Island Aloove area, Hassan vill. env. 12°31.2'N, 54°07.4'E, 221 m Jiři Hájek leg. 9 –10.xi.2010” (NMPC); 2 ♀♀, "YEMEN: Socotra Island Al Haghier Mts. Scant Mt. env. 12°34.6'N, 54°01.5'E, 1450 m J. Bezděk 12-13.xi.2010" (NMPC); 2 ♂♂, 1 ♀, "YEMEN, Socotra Island Hagher Mts., Scand Mt. env. montane evergreen woodland 16.-18.vi.2012 12°34.6'N, 54°01.5'E, 1450 m" / "SOCOTRA expedition 2012 J. Bezděk, J. Hájek, V. Hula, P. Kment, I. Malenovský, J. Niedobová & L. Purchart leg." (NMNHS, NMPC). All paratypes with label: "PARATYPE Parorthomus socotranus sp. n. Guéorguiev, Wrase & Farkač des. 2014" [black print on red label, black framed].

Diagnosis.

A brachypterous, black coloured species of Euchroina (Fig. 18), with moderately convex, amariform facies, with testaceus appendages, convex eyes, segment 11 of antennae not reaching basal margin of pronotum, elytra with very slight or reduced humeral denticle, elytral interval 3 with three to four (rarely two or five) discal setiferous punctures adjoining stria 3, with last puncture on posterior third of elytron, metaepisterna as long as wide, and median lobe of aedeagus curved to left distally, with apical lamella slightly emarginated at tip.

Values for sizes and ratios among specimens from the type series are shown in Table 1.

Description.

Body length 8.2-10.0 mm (9.2 mm in holotype); width 3.2-3.9 mm (3.6 mm in holotype), maximum width behind the middle of elytra. Head, pronotum, elytra, segments III–IV (in the most cases) of antennae, and ventral surface (without mouthparts) black in mature specimens, light to dark brown in immature specimens; labrum, mandibles, mentum, segments I–II and V–XI of antennae, and sometimes sides of pronotum testaceus; maxillary palpomeres, labial palpomeres, and labium rufous; coxae, femora, and tibiae of legs dark brown or testaceus, trochanters and tarsomeres mostly rufous.

Microsculpture distinct on the whole dorsal and ventral surfaces (including coxae, trochanters and femora), consisting of isodiametric and slight transversal meshes, more apparent in females (female specimens almost matt on dorsal surface, males somewhat shiny), reduced on the most part of the clypeus and gula.

Head noticeably longer and narrower with respect to the pronotum, frons smooth, frontal furrows well-marked, divergent posteriorly, reaching the level of anterior supraorbital punctures; neck without constriction posteriorly; eyes fairly large, convex, moderately prominent, with diameter as long as the combined length of segment I-II of the antennae, temporae short, as long as or shorter than half of eye diameter; paraorbital sulci moderately deep, encircling eyes behind; clypeus trapezoidal, separated from frons by fine suture, with anterior margin slightly concave; labrum rectangular; antennae moderately long, pubescent from second fourth of segment IV, the apex of terminal segment not reaching basal margin of pronotum; mentum transverse, deeply emarginate, with large labial pits, median tooth slightly bifid at tip, epilobes narrow, slightly projecting beyond lobes; submentum with medial setae, without lateral ones (Fig. 28).

Pronotum wide, transverse, sub-trapezoid, widest about middle, with margins distinctly, narrowly bordered (the bordering reduced in the middle quarter of apical margin, and sometimes in the middle of basal margin, just between the internal basal impressions); sides somewhat more constricted apically than basally, with two pairs of setiferous punctures, lateral punctures situated at about end of apical third, posterolateral ones situated near hind angles, near to lateral margin and close to basal margin; apical margin moderately emarginate, narrower than basal margin, fore angles rounded, moderately projecting; basal margin nearly straight, slightly concave in the middle, hind angles almost rectangular, rounded at tip; basal impressions somewhat variable in extension and size, internal ones always present, linear, narrow and falcate, diverging toward base, impunctate, deeper and longer than the outer ones, outer impression present or reduced becoming evanescent, when present then mostly faint, foveolate, somewhat punctate; disc slightly convex, midline well-impressed, long, not reaching both anterior and posterior margins.

Elytra sub-elongate, moderately convex, widest at about the second third, fused at suture; shoulders well-marked, obtusely angulate; basal margin complete, reaching stria 1 inwards, forming a very minute denticle at humerus; discal striae moderately impressed, impunctate, parascutellar striae distinct, striae 1-8 joining basal margin; intervals slightly flat, smooth, interval 3 with three to four (rarely two or five) setiferous punctures adjoining stria 3, with last puncture in posterior third of elytron, rarely in about middle of interval 3 (see also Variability); scutellar setiferous puncture present; hind wings reduced to small scales.

Prosternum, mesosternum, middle of metasternum, proepipleura, epipleura of elytra, and abdominal sternites (excl. sides of sternites 1-3) smooth, impunctate, proepisterna and sides of sternites 1-3 slightly punctured, mesepisterna, metepisterna, and sides of metasternum more or less roughly punctured; intercoxal process of prothorax subquadrate, distinctly bordered at sides and backwards; metaepisterna short, sub-quadrate, moderately narrowed toward behind, its anterior border longer than internal and posterior ones, as long as external border.

Abdominal sternites IV-VI with transverse basal sulci complete (continuous) and well-impressed, abdominal sternum VI with posterior margin rimmed throughout, with one pair of foveate setigerous punctures medially in males and two pairs in females.

Legs slender, relatively long; protibia apically moderately but abruptly enlarged at internal margin in males; mesotibia and metatibia straight in both sexes, mesotibia with slight inner callus distally in males; tarsomeres 1-5 glabrous dorsally, segment 5 setose ventrally; segments 1-3 of male protarsi moderately expanded.

Male genitalia (5 specimens dissected). Median lobe of aedeagus slender (Figs 19-20), narrower at middle, with basal part long, almost rectangularly bent behind apical part, narrowest at middle, from there toward apical lamella rectilinear, right external angle of apical lamella somewhat bent down, left external angle elevated (left lateral view), median lobe from middle part shifted to left, with right margin moderately convex, lengthwise appreciably elevated over left margin, left margin concave towards apex, apical lamella wide, rounded on left side, obtusely angled on right side, with a slight front concavity (dorsal view), ostium slightly deflected to right; right paramere narrow and elongate, smaller than left one, with a slanting lateral process (Fig. 21); left paramere conchoid (Fig. 22).

Female genitalia (3 specimens dissected). Ovipositor (Fig. 23), with valvifer more chitinized proximally and less distally, its distal margin having a setose and moderately chitinized area, basal stylomere large, conical, apical stylomere smaller, falcate, with two dorsolateral ensiform setae and one dorsomedial ensiform seta, sensorial pit distinct with two long nematiform setae; spermathecal complex (Fig. 24) with copulatory bursa proximally slightly gooseneck-like (this character not visible in Fig. 24), sper matheca with seminal canal and receptaculum slightly differentiated [undifferentiated type, according to Bousquet 1999: 35-36], receptaculum shorter than seminal canal, widened and slightly curved apically, appended spermathecal gland spherical, with elongate diverticulum.

Variability.

Interval 3 with three to four (rarely two or five) setiferous punctures adjoining stria 3, with last puncture in posterior third of elytron, rarely in about middle of interval 3. The number of punctures can increase to five or decrease to two, often the number of punctures of the left and the right elytron is unequal. Also the position of the punctures can somewhat vary. While the first two discal punctures always adjoin stria 3 (and so also the majority of the following punctures), sometimes the third puncture is located on the middle of interval or adjoins stria 2, rarely, the fourth discal pore is located on the middle of interval 3 or adjoins stria 2.

For variability of body size and indices see ‘Description’ and Table 1.

Etymology.

The specific epithet is an adjective, referring to Socotra, the island where the new species was collected.

Distribution.

Up to present only known from Socotra.

Ecology.

A mesotopic to eurytopic epigeic beetle, collected from the end of September to the first ten days of February, and on higher ground (Hagher Mts., Scand Mt. env., 1450 m) some specimens were also found in June. From the list of localities, the species seems to be quite widespread across Socotra from the mouths of wadis (near or far off the water) till the highest mountains. Referring on Bezděk et al. (2012), the dominant habitat at most of the mentioned localities is high shrubland with dominant Croton socotranus and Jatropha unicostata (in higher altitude with intermixed Boswellia spp., Dracaena cinnabari , Euphorbia arbuscula , etc.) ( Jiří Hájek, personal communication).

Systematic and biogeographic considerations.

The Socotra Archipelago is a Gondwanan continental fragment, which has experienced a long period of geological isolation. This landmass was separated from the Arabian plate during the rifting which began to open the Gulf of Aden in the Oligocene to Miocene epochs ( d’Acremont et al. 2006). It is supposed that Socotra was isolated from Arabia at least 16 million years ago ( d’Acremont et al. 2010). The high level of endemism found among the insects in Socotra ( Batelka 2012) is in accordance with the estimated geological age and the supposedly continuous stability of its ecosystems.

At present, it is difficult to ascertain whether Parorthomus socotranus sp. n. derived from ancestral populations on the Arabian mainland that probably reached Socotra by transoceanic dispersal in relatively recent geological times, or it is a descendent of an ancestor and evolved in situ in the course and after the separation of the island. Notwithstanding, a few taxonomic and biogeographic facts are consistent with the hypothesis that the species is not a phyletically young descendant of continental populations.

Combinations of distinguishing features (see ‘Diagnosis’, Key to the genera of the "African Series" of Euchroina ) clearly distinguish the new genus from the other related genera. However, some character states: 1/ mentum tooth bifid (Fig. 28); 2/ sides of pronotum straight or slightly convex posteriorly (Fig. 18); 3/ elytra with setiferous punctures in interval 3 (Fig. 18); 4/ intercoxal process of prothorax bordered; 5/ abdominal sternites V-VII with transverse sulci, complete and well-impressed; 6/ tarsomeres 1-5 of all legs glabrous dorsally; 7/ segment 5 of tarsomeres setose ventrally; 8/ aedeagus with sides nearly equally broadened in the distal half, with apical lamella wide, nearly rounded at tip (Fig. 20); 9/ appended spermathecal gland with diverticulum (Fig. 24), show that the new species may be related to two geographically “close” genera, the Afrotropical Abacillodes and the Mediterranean Orthomus . The two species from the first genus and the new species share characters 1-3 and 5-8. Some species from the second genus and Parorthomus socotranus sp. n. divide states 1-7 and 9 between, while the last taxon and Orthomus velocissimus s.l. possess all the listed character states.

The median lobe with sides nearly equally broadened along the distal half and apical lamella wide, rounded or semi-rounded at tip in the new species looks alike the median lobe in the Afrotropical Abacillodes (see Straneo 1988: 482, Fig. 1d, 484, Fig. 2b), as well as those in some Mediterranean taxa of Orthomus (see Mateu 1957, laminas I-IV, Machado 1992: 262, Fig. 100, Wrase and Jeanne 2005: 894-896, Figs 1b, 2b, 3b, 4b, 5b, 6b, 7b, Pupier and Coulon 2013: 224, Figs 1 c–e, 225, present paper Figs 5-8). In contrast, the median lobe of Parorthomus socotranus sp. n. has the distal half considerably curved to the left in dorsal aspect. Hitherto all the representatives of Orthomus and Abacillodes have the median lobe of the aedeagus straight or nearly straight. Based upon the condition in the other continental, African and Eurasian euchroines (aedeagus of Abacillius and Trichopedius not yet known or described), we consider the bent aedeagus to be an apotypic character in Parorthomus gen. n. The median lobes in the “gracilipes” group of Nesorthomus , with Nesorthomus gracillipes (Wollaston, 1854) and Nesorthomus berrai Battoni, 1987, have also the above discussed character state, more pronounced in the former and less pronounced in the second species (see Sciaky 1988: Figs 1b, 2b, Machado 1992: 264, Fig. 101A, Donabauer 2008: 111, Figs 1b, 2b, Serrano et al. 2009: 30, Figs 9b, 9d). This case is an instance of convergency. Change in this state has taken place independently in Nesorthomus , since the other six species from the genus have a straight median lobe of the aedeagus.

Besides, we infer that the presence of three to four discal setiferous punctures (by exception, two or five punctures on one elytron only) in the elytral interval 3 or stria 3, with the last puncture in posterior third of elytron, is another clear apotypic feature in the new taxon. This state occurs in no other species among the Old World Euchroina , except Parorthomus socotranus sp. n. The most species of the subtribe have two discal punctures in the elytral interval 3, as the second one lies at the posterior third of elytron. The species of Abacillius have no discal punctures on the elytron.

Parorthomus socotranus sp. n. has a unique combination of two apotypic characters, distal third of the aedeagus considerably curved to the left in dorsal aspect (i), and presence of 3-4 discal setiferous puncture in elytral stria 3/interval 3, with the last puncture situated in the posterior third of elytron (ii), which is indication for a long-time existing isolation and merit surely the erection of an own genus. The absence of close relative/s sharing together with the new species these two marked structural features exclude a close relationships and suggests that we deal with an ancient lineage which most probably arisen within the basic stem of the "African Series" of Euchroina (according to Will 2006) long time ago. As well, the lack of extant relatives, akin to the new species, in the Arabian Peninsula or somewhere else is a strong biogeographic argument, which certainly excludes geologically recent migration.

In spite of all, special character states and main ecologic preference in Parorthomus socotranus sp. n. suggest that it is phylogenetically closer to Orthomus and Abacillodes than to any other genus. The exact phylogenetic position within the euchroines can be disclosed only after investigation of more taxa, especially from the Old World, including also genetic technics and providing cladistic analysis, this could probably also identify its sister taxon.

The presence of large labial pits on the mentum is a trait in the new taxon that is worth noting. Each pit has a distinct, deep aperture, its diameter wider than the diameter of the labial pore, and both are situated more medially (Fig. 28). The distinct labial pits, destined to a particular function of use, seem to be a plesiotypic condition in Pterostichini ( Bousquet 1999: 33), as well in the Nearctic euchroines ( Frania and Ball 2007: 120). The species of Abacillius , Abacillodes and Orthomus possess no or small labial pits (Figs 25-27). In the second case, they have indistinct, shallow apertures, diameters similar to or smaller than the diameters of the labial pores, and both are situated more basally.

So far, 53 species of ground beetles have been recorded from the Socotra Archipelago ( Felix et al. 2012, present work). Parorthomus socotranus sp. n. is the only representative of the tribe Pterostichini and the second carabid endemic form at genus level found in this insular fragment ( Wranik 2003, Felix ibid.).