Trechus “ subnotatus

Kostova, Rumyana & Bekchiev, Rostislav, 2025, New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973, Zootaxa 5661 (4), pp. 538-552 : 545-549

- Taxonomic challenges in the identification of the Trechus “ subnotatus ” group’s taxa in the Balkans

Material studied: T. cardioderus cardioderus above mentioned six specimens and ROMANIA: 1 ♂ ‘ Flaischar , Orszova’ (NMPC); T. cardioderus athonis above mentioned ten specimens (NMPC); T. cardioderus balcanicus Jeannel, 1927 : AUSTRIA: 1 ♂ ‘ Rotenturum / P. Deubel’ (NMPC); BOSNIA AND HERZEGOVINA: 1 ♂ ‘ Bosnien , Mt. Igman 1400 m, Sarajevo, 16.V.1990 Battoni’ (BFUS); 1 ♂ ‘ Bosnia , Trebević, V.1907 ’ (NMPC); 1♂ ‘ Hercegovina, Tara pl., Babina gora, 01.VI.1967, Mařan’ (NMPC), 1 ♂ ‘ Bosna , Treskavica, 1200–1500, 19.VII.1974, K. Hůrka’ (NMPC); BULGARIA: 1 ♂ ‘ Stara Planina , Chumen les, 1250–1400m, 19.VII.1987, leg. K. Hůrka’ (NMPC); 1 ♂ ‘ Stara planina, Bukovec env. Les, potok, 900–1000 m, 20.VII.1987, K. Hůrka’ (NMPC); 1 ♂ ‘ Stara Planina , Chumerna les 1300– 1400 m, 21.VII.1987, K. Hůrka’ (NMPC); 1 ♂ ‘ St. Planina , El. Tvard., Planina, les 18.VII.1987, leg. K. Hůrka’ (NMPC); 1 ♂ ‘ Stara planina, Berkovska pl. Kom hut, 1650m, 23.VII.2000, P. Moravec lgt.’ (BFUS); 1 ♂ ‘ Stara planina, Berkovitsa-Kom hut, 1000–1200m, 25.VII.2000, P. Moravec lgt.’ (BFUS); 1 ♂ ‘ Stara planina, Gorni Lom-mt. Midzhur, 100–1500 m, 27.VII.2000, P. Bulirsch’ (BFUS); CROATIA: 1 ♂ ‘ Krajina , 05.IV.1905 ’ (NMPC); ROMANIA: 1♂ ‘ Mt. Căpătânii , Cheile Oltețului-Polovragi, 650m, 17.VI.1998, P. Moravec lgt’.; 5 ♂♂ same as previous but 650–800 m (BFUS); 2 ♂♂ ‘ Mt. Căpătânii , valea Cheia, vf. Stogsoare, env., 750–900 m, 6–7.VII.1999, P. Moravec lgt.’ (BFUS); 1 ♂ ‘ Mt. Căpătânii , valea Cheia, I.F. Luncile, Oltetului env., 650 m, 8.VII.1999, M. Jaros lgt.’ (BFUS); 1 ♂ ‘ Muntii Fagaraf Ului , Biela Cascada, 2200 m, VIII.97, lgt. Snizek’ (BFUS); SERBIA: 1 ♂ ‘ Jugoslavija , Serbia , Maljen, Divcibare-sedlo, 750–900 m, 20.V.1991, P. Moravec lgt’ (BFUS); 1 ♂ same as previous but 700–800m, 19.V.1991 (BFUS); SLOVENIA: 1 ♂ ‘ Sv. Lovrenc , VII.1934 ’ (NMPC); 1 ♂ ‘ Bor. mont., Ožbalt 5– 6.X.2002, J. Bednář lgt.’ (BFUS); 2 ♂♂ ‘ Kobansko , Hude luknja env., u potoka, pr. Radlje ob Dravi, 7.V.1992, R. Mlejnek lgt.’ (BFUS). T. pilisensis pilisensis Csiki, 1918 : AUSTRIA: 2 ♂♂ ‘ Schoberstein , Austr. Sup, Mont. Petz ,,coll. Lokay’ (NMPC); 1♂ ‘ Wein , Umg. Rekawinkel,coll. Lokay’ (NMPC); CZECHIA: 1♂ ‘ Boh. Krkonose Obri dul, 27.VII.1956, Hůrka’ (NMPC); 1 ♂ ‘ Boh. Sumava , Stozec-les, 2.V.1987, K. Hůrka ’(NMPC); 2 ♂♂ ‘M. bor. 8.IX.1969, Dolni Morava, Mlynar lgt.’ (NMPC); HUNGARY: 1 ♂ ‘ Hung. mer. Mecsek Mlsinateo, 26.V.1964, Hůrka’ (NMPC); SLOVAKIA: 1 ♂ ‘ Slov. Or. Hrubku, potok, 700– 600 m, 10.VII.1961, Hůrka’ (NMPC); SLOVENIA: 1 ♂ ‘ Kalobje , 30.11.1928, coll. Lokay’ (NMPC); T. binotatus Putzeys, 1870 : ITALY: 1 ♂ ‘ Vallombrosa’ (NMPC); T. asiaticus Jeannel, 1927 : BULGARIA: 1♂ ‘ Strandzha pl, Bulg., VII.34 Pfeffer’ (NMPC); 4 ♂♂ ‘ Zeitinburun (= Maslen nos), Bulg. Orient., VI.33 Mař. Táb’ (NMPC); TURKEY: 2 ♂♂ ‘ Bursa, Asia Min. , Dr. Jurecek 1931’ (NMPC); 1♂ ‘ Suluhan , Toros, Anat. 11.VII.1947, Exp. N. Mus. ČSR’ (NMPC); T. byzantinus Apfelbeck, 1901 : TURKEY: ‘ Belgrada. Wal., Turkei, ex. coll. Paganetti, coll. Kouřil’ (NMPC). The newly obtained morphometric data were pooled with the previous sample of Kostova and Bekchiev (2023), containing data for T. cardioderus irenis Csiki, 1912 (36 ♂♂); T. cardioderus athonis (58 ♂♂); T. cardioderus balcanicus Jeannel, 1927 (5 ♂♂); T. asiaticus Jeannel, 1927 (4 ♂♂); T. strandzhensis Kostova & Bekchiev, 2023 (19 ♂♂); T. byzantinus 3 ♂♂; T. asiaticus (4 ♂♂).

The pooled dataset (n = 191 males) was subjected to canonical stepwise discriminant analysis to assess morphological relationship among the studied taxa. Fig. 6 , presents the results of this analysis.As was expected, there was a high degree of overlap and gradient distribution but also some ordering along the gradient of the taxa studied. The first canonical discriminant function accounted relatively small amount of the variation between groups— 49%, canonical correlation coefficient Rc=0.68, Wilks’ Λ = 0.26, χ² (df. 35) = 249.73, p <0.001. The extremes of the gradients along the first canonical function are occupied by T. asiaticus and T. strandzhensis . The second canonical function explained 35% of the variation, canonical correlation coefficient Rc=0.61, Wilks’ Λ = 0.48, χ² (df. 24) = 135.94, p <0.001. The ordering of the centroids was T. byzantinus , T. cardioderus athonis , T. asiaticus , and T. strandzhensis , from the one side and the very close centroids of T. cardioderus sensu stricto, T. cardioderus balcanicus , T. cardioderus irenis , and T. pilisensis pilisensis from the other ( Fig. 6 ).The indices that remained in the analysis with the highest relevance for the discrimination were L, PW/PBW, EW/PW, EL/EW, L/PW, showing the body size, pronotum width and elytra length and width relations as key characters for taxa delimitation. However, they did not have a good discriminant value, with the cross-validation analysis showing that only 53% of the group specimens were correctly classified. The highest error was for T. byzantinus , where all of the four specimens were classified as T. cardioderus athonis . followed by T. pilisensis , where 50% of specimens were classified as T. cardioderus irenis , 30% as T. cardioderus athonis and the rest as T. cardioderus balcanicus , and by T. cardioderus cardioderus , where 43% of specimens were classified as T. cardioderus balcanicus and the rest as T. cardioderus athonis (28.6%) and T. cardioderus irenis (28.6%) ( Table 2 ). These data demonstrate that misidentification is highly probable, when based exclusively on external morphology. The identification key for the T. “ subnotatus ” group by Jeannel (1927) is based mainly on the size, shape and colour of the pronotum and elytra. Our study demonstrates that reliable identification based exclusively on exterior characters—without male genitalia morphology—is nearly impossible. Furthermore, even the morphology of the median lobe may exhibit variations, introducing uncertainty in the determination of the group’s taxa. Fig. 7 presents comparative series of the median lobes of these taxa, all possessing a curved copulatory piece, demonstrating gradual morphological transitions among taxa.

With additional material on the “ subnotatus ” group from the Balkans, the documented variation in the male genitalia morphology will likely expand, particularly among the subspecies of T. cardioderus . Even now, we found that the morphology of the median lobe of the T. pilisensis specimens in the NMPC collection ( Fig. 7 : G–I) does not correspond exactly to the drawing by Jeannel (1927: 453 Fig. 1075). In these specimens, the apical part of the aedeagus is slightly curved ventrally, similar to that of T. cardioderus transdanubiensis Nonveiller, Pavićević, Popović, 1994 described and, to date, reported only from Serbia ( Nonveiller et al. 1994: 14 Figs. 5–6 ). Nonveiller et al. (1994) did not make a drawing of the copulatory piece of the median lobe, nider describe it in their paper. We assumed that if there is a differentiating character between them, it should be that the copulatory piece. However, this is an assumption for now, and uncertainty remains until the types of both taxa are studied and a clear difference is described.

The present study of the collection at the NMPC has extended the data for T. cardioderus athonis , T. cardioderus goleshnicensis , and T. subnotatus subnotatus obtained in our previous studies of the collections at the MNHN (coll. Jeannel), SDEI, HNHM, NMNHS and BFUS. Our morphological studies reveal no consistent diagnostic differences among these three taxa due to their extensive variability, suggesting they will be likely synonymized in the future. The diagnostic characters given by Jeannel (1927) to distinguish these three taxa have become unreliable due to increasing overlap with larger sample sizes. Similarly, the original descriptions of these taxa lack taxonomic precision to rely on. The three taxa share the following characters: a relatively large, transverse pronotum with oval lateral margins, shortly and slightly sinuate before the small, nearly straight and only slightly protruding posterior angles; elongate elytra with maximum width at the second half of the elytra; reduced posterior wings; median lobe of male genitalia with prolonged apex in lateral view, and wide, straight apical lamella (not or only slightly narrowing) in dorsal view. The colouration of the elytra in T. cardioderus athonis and T. subnotatus varies (monocoloured, with humeral elongate spots and/or two anteriorly rounded spots).

According to Jeannel (1927), the diagnostic differences between T. cardioderus athonis and T. cardioderus goleshnicensis are in the apex of the aedeagus in lateral view (slightly curved ventrally in the former and straight in the latter) and a very narrow pronotum in T. cardioderus goleshnicensis . Between them and T. subnotatus , he pointed only one difference in the copulatory piece of the median lobe, having a strongly upward-curved distal part in T. cardioderus athonis and T. cardioderus goleshnicensis while almost straight copulatory piece in T. subnotatus . We revealed that, all examined specimens from the Balkans in the studied collections previously labelled as T. cardioderus goleshnicensis or T. subnotatus turned out to be T. cardioderus athonis , according to the criteria of Jeannel (1927). The ratio of the width of the prothorax to the width of the elytra (EW/PW) varies strongly in the specimens of our T. cardioderus athonis sample. The EW /PW index ranges from 1.56 to 1.60 in the specimens from the type series (4 ♂ GREECE, Athos, SDEI), as well as from 1.39 to 1.69 in the total Balkan sample and it overlaps with that of the four specimens identified as T. cardioderus goleshnicensis by Jeannel in his collection (2 ♂♂ MONTENEGRO, Zljeb planina, 2 ♂♂ Besina gora Bielasica (MNHN, coll. Jeannel) with EW/PW ranging from 1.43 to 1.44 as was shown in our previous study ( Kostova & Bekchiev 2023).

The diagnostic value of the straight apex of the median lobe in lateral view in T. cardioderus goleshnicensis also remains uncertain due to the previous finding of syntopic specimens of T. cardioderus athonis from the Belasitsa Mts. in Bulgaria, with variations from curved downwards to straight apex in lateral view ( Kostova & Bekchiev 2023). The upward curvature of the distal part of the copulatory piece of the median lobe, a differential characteristic between T. cardioderus subspecies and T. subnotatus , is also sometimes difficult to discern with certainty, especially in lateral view on microscope slides due to frequent displacement and rotation. Figure 8 shows variation in the median lobe (mounted on microscopic slides) of specimens identified by Jeannel as T. subnotatus subnotatus (Zelinica, Dalmatia; Cephalonia; Pesio) and T. subnotatus pallidipenis (Athica) —from his collection at MNHN. Despite the compromised quality of the slides and the fixed lateral positioning, the similarity between the aedeagus of T. subnotatus and T. cardioderus athonis is clearly observable. Additionally, the upwardly curved distal part of the copulatory piece in T. subnotatus pallidipenis —described as an unicolorous variant and now junior synonym of T. subnotatus —can be seen. However, at this stage of our research, we cannot be confident in our hypothesis that the three taxa represent a single, highly variable species, nor can we resolve the uncertainty regarding the specific independence of T. cardioderus . Further studies are needed based on more extensive material, especially from Greece and Macedonia, and fresh ethanol-preserved specimens from the entire ‘subnotatus’ group range for combined morphological and molecular analysis of species boundaries and phylogenetic relationships.

Figures

FIGURE 5. Map of the currently known distribution of Trechus cardioderus athonis Schatz.

FIGURE 6. Scatter plot of the first two canonical discriminant functions for some taxa of the Trechus “subnotatus” species group in the Balkans.

FIGURE 7. Median lobe of the male genitalia (lateral and dorsal views) of taxa of the Trechus “subnotatus” group: A–C— Trechus cardioderus cardioderus Putz. (Slovenia, Radoha, NMPC); D—Trechus binotatus Putz. (Italy, Vallombrosa, NMPC); E—Trechus cardioderus irenis Csiki (Bulgaria, Central Stara Planina Mts., according to Kostova & Bekchiev 2023); F— Trechus cardioderus balcanicus Jeann. (Bulgaria, East Stara Planina Mts., according to Kostova & Bekchiev 2023); G–I— Trechus pilisensis pilisensis Csiki (G—Slovakia, M. Bor; H—Czechia, Skryje; I—Austria, Schobrstein, NMPC); J–O—Trechus cardioderus athonis Schatz. (J—Greece, Yoanina; K—Greece, Attica; L—Montenegro, Bay of Kotor; M—Greece, Cephalonia; N—Bulgaria, Pirin Mts., Oshtava Vill.; O—Bulgaria, Šarlir; NMPC); P—Trechus strandzhensis Kost. & Bekch. (Strandzha Mts., according to Kostova & Bekchiev 2023).

FIGURE 8. Median lobe of the male genitalia (lateral view) of Trechus subnotatus subspecies on microscopic slides from the Jeannel collection (MNHN): A–C—Trechus subnotatus subnotatus Dej.; D—Trechus subnotatus pallidipennis Schaum.