Trechus Abunetrechus Schmidt & Faille, 2023

Faille, Arnaud, Hofmann, Sylvia, Merene, Yeshitla, Hauth, David, Opgenoorth, Lars, Woldehawariat, Yitbarek & Schmidt, Joachim, 2023, Explosive radiation versus old relicts: The complex history of Ethiopian Trechina, with description of a new genus and a new subgenus (Coleoptera, Carabidae, Trechini), Deutsche Entomologische Zeitschrift 70 (2), pp. 311-335 : 311

Trechus Abunetrechus Schmidt & Faille nov. subgen.

Type species.

Trechus bipartitus Raffray, 1885, herewith designated.

Diagnosis.

Representative of Trechina and Trechus s. l. sensu Jeannel (1926, 1927, 1928) due to presence of bidentate mandibles (absence of retinacle), dorsally closed aedeagal median lobe, well-developed compound eyes, protibia glabrous on anterior surface, presence of two elytral dorsal setae situated in third interval, elytral intervals glabrous, 4+2+2 pattern of umbilicate setae, and two basal tarsomeres of male dilated. Externally, Trechus Abunetrechus subgen. nov. reminders a non-specialised high-altitude Trechus of moderate body size, short mandibles, antenna and legs, moderately large eyes, rounded humeri, short metepisternae and hindwings reduced to short stubs. Trechus sensu lato, Trechus Abunetrechus subgen. nov. is characterized by the combination of following character states: bisetose clypeus (Figs 18 , 20 , 22 ), smooth tempora, pronotum with fully rounded laterobasal angles and with laterobasal setae markedly protruded anteriorly (Figs 18 , 20 , 21 ), elytral striae 3 and 4 merging at level of the anterior discal seta (Fig. 23 ), elytral preapical seta of the third interval present and situated about at level of the elytral apical tenth, protibia with longitudinal groove on external surface; aedeagus with two moderately sclerotized portions of the endophallus arranged one behind the other in apical half of the median lobe (Figs 24-29 ).

Etymology.

The subgenus name combines the name of the Abune Yosef Massif in northern Ethiopia, where the species of this subgenus occur, with the name of the genus Trechus .

Description.

Head: Size averaged for Trechus sensu lato, without pilosity. Mandibles short, with dentition pattern as in Trechus sensu stricto. Labrum with apical margin moderately emarginated, with six setae near apical margin. Clypeus each side with one long seta (Figs 18 , 20 , 22 ; very seldom with an additional very fine seta situated interior of one of the primary setae). Eyes moderately large, convexly protruded, more than two times as long as tempora, latter moderately convex (Figs 18 , 20 , 22 ). Two supraorbital setae each side in normal position for Trechus . Supraorbital furrows moderately deep and almost evenly bent throughout. Tempora moderately convex, markedly wrinkled to the neck, smooth. Mid of head convexly elevated. Antennae short, with third antennomere slightly longer than pedicellus. Suborbital seta present. Apical tooth of mentum truncate or slightly bifid, sensory pits of mentum present but very small; submentum with 4-7 setae.

Prothorax: Pronotum with size averaged for Trechus sensu lato, without pilosity, slightly transverse, broadest distinctly before middle, with lateral margin completely rounded towards base, and with laterobasal angles indistinct. Basal margin (between insertion points of laterobasal setae) distinctly broader than apical margin. Disc markedly convex. Anterior margin slightly or moderately concave with anterior angles shortly rounded, moderately protruded. Basal margin straight or slightly convex in middle and with outer quarters markedly shifted anteriorly towards lateral margin (Figs 18 , 20 , 21 ). Lateral margin convexly rounded throughout; laterobasal angle fully rounded or marked as a very small blunt tooth. Marginal gutter very narrow throughout. Median longitudinal impression slightly incised, disappearing near apex and base, not deepened within area of posterior transverse impression. Anterior and posterior transverse impressions very shallow, smooth or (posterior transverse impression) sometimes finely wrinkled. Laterobasal foveae rather small, moderately impressed, smooth. Lateral and laterobasal setae present, with the former situated near maximum width of pronotum. Proepisternum glabrous and smooth.

Pterothorax: Elytra without pilosity, slender ovate, markedly domed towards disc, not flattened in middle of disc, in dorsal view broadest slightly posterad middle, shoulders flatly rounded, apical sinuation very slightly developed or indistinct, apex rounded or marked as an obtuse apical angle. Parascutellary stria short to moderately long, free; striae 1-8 almost complete, moderately deep impressed in middle of disc, less deeply towards sides, disappearing near base, crenulated, striae 3 and 4 merging at level of the anterior discal seta; intervals slightly convex. Recurrent preapical stria deep, long, connected with the apex of the fifth stria. Parascutellar seta present. Anterior discal seta situated at merging point of the 3rd and 4th stria, near the end of the anterior elytral 5th (Fig. 23 ); second discal seta located at the 3rd stria somewhat behind elytral middle; posterior discal seta (= subapical seta near end of 3rd stria) present, located about 1/10 of elytral length from elytral apex; subapical seta of the recurrent stria isolated, removed from this stria by distance of 1-2 diameters of the setiferous pore. Number and positions of the setae of the marginal umbilicate series as in Trechus s. str. Metepisternum very short, glabrous and smooth, with outer margin about as long as anterior margin.

Legs: Short and moderately robust. Protibia distinctly dilated towards apex, straight, glabrous, with longitudinal groove on dorsal surface complete. Two basal protarsomeres of males dilated and dentoid at the inner apical border. Chaetotaxy as in Trechus sensu stricto.

Male genitalia (Figs 24-29 ): Aedeagal median lobe moderately large, in lateral view markedly curved, with apical lamella short, latter with distinct terminal capitulum; basal bulb and saggital aileron averaged. Endophallus with a moderately large, moderately sclerotized folding structure (copulatory piece) in the shape of a half-open cylinder or cone which is located in apical half of the median lobe and directed to its longitudinal axis, and with the open part of the copulatory piece facing ventrad. Apicad of this piece, an additional slightly more strongly sclerotized folding structure is developed which is shaped as a small plate (best visible in lateral view); the basal part of this piece overlaps with the apex of the more dorsal copulatory piece. Parameres with 2-4 apical setae.

Remarks.

In his redescription of Trechus bipartitus , Jeannel (1927) noted the presence of a single copulatory piece which is characterized by a long sinusoidal appendix. However, in his figure of the left lateral view of the copulatory piece ( Jeannel 1927: 195) he merged the more strongly sclerotized folding structure near median lobe apex with the more basad located larger copulatory piece which leads to the impression of a single, very long piece.

Distribution.

Northern Ethiopia Plateau (Fig. 1 ): Three species are known so far, two from Mt. Abune Yosef ( T. bipartitus Raffray, T. lalibelae Quéinnec & Ollivier) and one from the Guassa Plateau ( T. habeshaicus Quéinnec & Ollivier).

Relationships and identification.

Based on the molecular data, Trechus Abunetrechus subgen. nov. is representative of a clade comprising Anchotrechus Jeannel from Tenerife, the Trechus subgenus Arabotrechus Mateu from Yemen, and the Trechus subgenus Meruitrechus Jeannel from Mt. Meru, Tanzania (Fig. 3 ; in the following called the AAMA clade). Trechus Abunetrechus subgen. nov. differs from all species groups of the AAMA clade by bisetose clypeus. A quadrisetose clypeus was hypothesized plesiomorphic character state in Trechini ( Schmidt et al. 2021). Within this tribe, a bisetose clypeus is also developed in the genus Omalodera Blanchard from Chili, the Caucasian genus Alanorites Belousov of the Neotrechus Phyletic Series, and two Epaphiopsis Uéno species occurring in the central Himalaya ( Belousov 1998; Naito 2023). However, this character state has to be considered homoplasic because none of these taxa cluster within Trechus sensu lato ( Faille et al. 2013, 2021; Maddison et al. 2019, see Fig. 2 in this paper). Trechus Abunetrechus subgen. nov. additionally differs from all other species of the AAMA clade by rounded pronotal laterobasal angles, from Meruitrechus by presence of the elytral preapical seta of the third interval, the isodiametric sculticells on elytra less deeply engraved, and eight striae well marked, from Anchotrechus by smaller and stouter body, glabrous elytra and much shorter aedeagal median lobe, and from Arabotrechus by the smaller body size, presence of a second discal setae (missing in Arabotrechus , as well as in T. aethiopicus and some species of Elgonotrechus Jeannel. Trechus Abunetrechus subgen. nov. shares the elytral striae 3 and 4 merging at level of the anterior discal seta with Arabotrechus (based on a single investigated specimen; larger series would be necessary to confirm the stability of this character).

Figures

Figure 1. Map of Ethiopia showing the main topographic features of the country. Seven prominent volcanic massifs which are discussed in the text are highlighted. The base map was downloaded from www. freeworldmaps. net (01 - 07 - 2023).

Figure 2. Ultrametric time-calibrated phylogeny of Trechini beetles and outgroups (basal part of the tree, continues in Fig. 3). The tree was obtained from BEAST 2 based on the concatenated sequence data and using two age constraints (for details see text). Black circles and stars at branch nodes refer to posterior probabilities ≥ 0.98 and bootstrap values> 75, respectively. Grey bars specify the 95 % HPD of the respective node age. Collapsed, colored trechine clades refer to previous results of Faille et al. (2013). The southern hemisphere Duvaliomimus - Paratrechus clade with the Ethiopian endemic Baehria gen. nov. is highlighted ochre.

Figure 3. Subtree of the ultrametric time-calibrated phylogeny of Trechini beetles as shown in Fig. 2 (see there for details). Collapsed, colored clades refer to previous results of Faille et al. (2013). Clades which include Ethiopian Trechus (sensu lato) species are highlighted by different colors (see text for details).

Figures 17 - 20. Trechus subgenus Abunetrechus nov., dorsal aspect of body (17, 19), head and pronotum (18, 20). 17, 18. T. bipartitus Raffray; 19, 20. T. lalibelae Queinnec & Ollivier. The small white circles in Figs 18 and 20 mark the insertion points of the clypeal setae.

Figures 21 - 23. Trechus subgenus Abunetrechus nov., dorsal aspect of body (21) and head (22), and anterior part of left elytron (23). 21, 22. T. habeshaicus Queinnec & Ollivier; 23. T. bipartitus Raffray. The small white circles in Fig. 22 mark the insertion points of the clypeal setae; the arrow in Fig. 23 points to the insertion of the anterior elytral discal seta.

Figures 24 - 29. Trechus subgenus Abunetrechus nov., aedeagus in left lateral aspect (24, 26, 28) and dorsal aspect (25, 27, 29). 24, 25. T. bipartitus Raffray; 26, 27. T. lalibelae Queinnec & Ollivier; 28, 29. T. habeshaicus Queinnec & Ollivier.