On the diversity of subterranean beetles of the Dinarides: new leiodid taxa (Coleoptera: Leiodidae) from Serbia

Three subterranean leptodirine leiodid taxa, viz., Bozidaria Ćurčić & Pavićević gen. nov., Bozidaria serbooccidentalis Ćurčić & Pavićević gen. et sp. nov. and Proleonhardella (Proleonhardella) tarensis Ćurčić & Pavićević sp. nov., are described and diagnosed. Bozidaria Ćurčić & Pavićević European Journal of Taxonomy 782: 55–81 (2021) 56 gen. nov. belongs to the phyletic series of “Leonhardella”. The new beetle taxa differ from their closest relatives in numerous morphological characters. They most likely belong to phyletic lineages of Pliocene age. The new leiodid taxa are endemic to the Dinaric mountain chain of western Serbia. Keys to the leptodirine leiodid genera of the phyletic series of “Leonhardella” and to the taxa of the genus Proleonhardella Jeannel, 1910 are included.

In the chapter on the family Leiodidae in the recent Catalogue of Palaearctic Coleoptera, Perreau (2015) reported the presence of both species of Proleonhardella solely for Serbia (Pešter Plateau). In reality, the type localities of both species are not situated on the Pešter Plateau, but in its surroundings. Additionally, they inhabit the territory of Montenegro, as documented by Pavićević et al. (2012) and Hlaváč et al. (2017). Namely, P. (P.) hirtella, besides its type locality, is known to inhabit three caves and pits near the towns of Prijepolje and Priboj (southwestern Serbia) and one pit near the town of Pljevlja (northern Montenegro) (Pavićević et al. 2012). On the other hand, P. (P.) remyi, besides its type locality, lives in numerous caves and pits in the area of Kamena Gora and near the towns of Prijepolje and Priboj (southwestern Serbia), as well as in two caves and one pit near the town of Pljevlja (northern Montenegro) (Pavićević et al. 2012). The two species cohabitate in some caves and pits (five such localities are known), where the populations of the latter are more abundant (Pavićević et al. 2012). Additionally, the type locality of P. (P.) remyi in northern Montenegro is erroneously reported by Perreau (2000) to be situated in Serbia.
On the basis of the current distribution of Serbian endogean and cave-dwelling leiodid taxa, we assumed that some taxa new to science (genera and species) might be discovered in certain karstic areas of the Dinaric Alps of Serbia, which were so far not investigated and from which no taxa of leiodids from the underground have been documented. Type specimens were studied in the laboratories of the Institute of Zoology, University of Belgrade -Faculty of Biology, Belgrade, Serbia. The beetles were dissected, analysed in detail and photographed. Dry individuals were glued onto rectangular paper mounting cards. Extracted genitalia were fixed in a medium composed of Canada balsam and toluene and put onto rectangular transparent plastic mounting cards placed on the same entomological pin together with the mounting card of the dry individual.
Observations were conducted with a Carl Zeiss-Stemi 2000 binocular stereo microscope. A Nikon SMZ 18 stereo microscope combined with a Nikon DS-Fi1c digital camera, as well as a Leica DMLS light microscope combined with a Leica DC 300 camera, were used to photograph morphological details of the whole specimens and genitalia of new beetle taxa. The detailed morphology of the new taxa was imaged using scanning electron microscopy (SEM) at the Photonics Center, Institute of Physics Belgrade, University of Belgrade. SEM micrographs were made using a MIRA3 FEGSEM field-emission scanning electron microscope (FESEM) (Tescan, Brno, Czech Republic) in high vacuum mode, at a voltage of 15 kV. All samples were sputter coated with gold/palladium for 30 seconds. The index of intensity of the electron beam was 15.00. Pressure in the column was about 127 MPa.

A1/A2
= ratio of length of antennomere I to length of antennomere II A3/A2 = ratio of length of antennomere III to length of antennomere II A3/A5 = ratio of length of antennomere III to length of antennomere V A7/A6 = ratio of length of antennomere VII to length of antennomere VI A7/A8 = ratio of length of antennomere VII to length of antennomere VIII A8LW = ratio of length to width of antennomere VIII A9LW = ratio of length to width of antennomere IX A9/A8 = ratio of length of antennomere IX to length of antennomere VIII A10LW = ratio of length to width of antennomere X A11LW = ratio of length to width of antennomere XI A11/A9+A10 = ratio of length of antennomere XI to length of antennomeres IX and X combined EL/EW = ratio of length of elytra (as linear distance between base to apex of elytra along median suture) to maximum width of elytra EL/PL = ratio of length of elytra (as linear distance between base to apex of elytra along median suture) to length of pronotum HL/HW = ratio of length of head (as linear distance between anterior margin of clypeus to occipital carina) to maximum width of head M = mean value for certain measurements P1LW = ratio of length to width of protarsomere I PB/AM = ratio of length of pronotal base to length of anterior pronotal margin PL/PW = ratio of length of pronotum to maximum width of pronotum PL+EL/AL = ratio of length of pronotum and elytra combined (as linear distance between anterior pronotal margin to apex of elytra along median suture) to total antennal length R = range of measured values TL = maximum body length from anterior margin of clypeus to apex of elytra along median suture

Diagnosis
Bozidaria gen. nov. is most closely related to the following Dinaric genera of the group Théléomorphes belonging to the phyletic series of "Leonhardella" (Jeannel 1924): Proleonhardella, Blattochaeta Reitter, 1910, Augustia Zariquiey, 1927and Pholeuodromus Breit, 1913. These genera share a similar body form, the presence of tetramerous tarsi in males, the absence of a comb on anterior tibiae, the first antennomere clearly shorter than the second antennomere, apically widened distal antennomeres, the absence of sutural striae, and the presence of a similar type of aedeagus.
The new genus differs from its closest relatives in the body shape (elliptical, elongate vs bathyscioid, oval/ovoid, mostly wide in Proleonhardella), TL (R 2.51-2.80 mm vs R 4.0-5.5 mm in Blattochaeta and R 3.8-4.6 mm in Pholeuodromus), body pubescence (short, recumbent vs long, erect in Blattochaeta), shape of antennae (elongate, thin, including distal antennomeres vs short, distal antennomeres wide, barely longer than wide in Proleonhardella), length of antennae (exceeding the middle of the body vs reaching, but not exceeding the middle of the body in Augustia and not reaching the middle of the body in Pholeuodromus), presence/absence of mesosternal carina (present vs absent in Augustia), shape of mesosternal carina (with no concavity on its anterior border, not atrophied vs with a concavity on its anterior border in Blattochaeta and atrophied posteriorly in Pholeuodromus), shape of lateral pronotal margins (arcuate vs weakly convex in Augustia), position of maximum pronotal length (sub-basally vs at base in Pholeuodromus), ratio of pronotum width to elytral width (pronotum slightly narrower than elytra vs pronotum as wide as elytra in Blattochaeta and Pholeuodromus and pronotum clearly narrower than elytra in Augustia), shape of elytra (more rounded, gradually narrowed distally vs less rounded, more pronouncedly attenuated distally in Augustia), shape of aedeagus (long, elongate vs short, wide in Blattochaeta and Augustia and mostly wide in Proleonhardella), shape of basal bulb (elongate, narrow vs short, rounded in Proleonhardella, Blattochaeta and Augustia) and its basal projection (long vs short in Proleonhardella and Augustia), and shape of parameral apex (narrow vs widened in Blattochaeta) (Jeannel 1910(Jeannel , 1924(Jeannel , 1930(Jeannel , 1931(Jeannel , 1934Reitter 1910;Breit 1913;Zariquiey 1927;Knirsch 1928;Guéorguiev 1976).

Etymology
This genus is named after the late Academician Božidar Ćurčić, a well-known Serbian biospeleologist and zoologist.

Description
Habitus. A small-sized elliptical leptodirine with short and wide head, transverse pronotum and elongate obovoid elytra. Blind, reddish-brown, body shiny, densely pubescent, dorsoventrally convex, finely punctate. Pubescence composed of short yellow hairs, on pronotum and elytra recumbent, while on head erect. Legs and antennae long and slender, densely pubescent. Microsculpture composed of isodiametric meshes.
Head. Anophthalmous, of almost equal length and width. Antennae inserted medially on head, elongate, thin, apically widened and flattened, exceeding middle of body, reaching basal third of elytral length. Antennomere I shorter than antennomere II. Antennomere III shorter than antennomere II and longer than antennomere IV. Antennomeres IV-VI of similar length. Antennomere VII elongate, apically widened. Antennomere VIII short, elongate, oval. Ultimate antennomere slender, ovoid, about as long as antennomeres IX and X combined. Occipital carina present.
tHorax. Pronotum almost twice as wide as long, with arcuate and well-rounded lateral margins, slightly narrower than elytra, widest slightly prior to pronotal base. Mesosternal carina well-developed, with no furrow, high, obtuse-angled, with an apical tooth.
legs. Extended and slender. Fore tarsi tetramerous. Male protarsi dilated. Tibiae with spines on external edges. No comb on external edges or apical parts of protibiae. Meso-and metatibiae with no apical baskets.
abdomen. Median lobe of aedeagus slender, rounded sub-terminally, with an elongate triangular apex. Basal bulb elongate, narrow, with a long sub-triangular basal projection. Each paramere longer than median lobe, thin, sub-terminally widened, with three apical setae.

Distribution
The new genus is currently known to inhabit deep soil on Mt Bobija and the Simina Jama Pit on Mt Povlen in the surroundings of the town of Ljubovija, western Serbia. It is probable that it might be present both in the soil and caves of the adjacent areas.  (Fig. 1N)

Diagnosis
The genus is currently monotypic and therefore a differential diagnosis for Bozidaria serbooccidentalis gen. et sp. nov. cannot be provided.

Etymology
The species is named after western Serbia, where its type locality and known localities are situated.  (Fig. 2).

Bionomy, distribution and type locality
The type specimens were collected in traps for endogean fauna (cans) baited with rotten meat placed in the deep soil on Mt Bobija, near the town of Ljubovija, western Serbia, as well as by pitfall trapping with rotten meat as bait in the deep, totally dark parts of the Simina Jama Pit, village of Gornje Košlje, Debelo Brdo saddle, Mt Povlen, near the town of Ljubovija, western Serbia (Fig. 9). The type locality on Mt Bobija is located on its northern slope, at an altitude of 1000 m a.s.l., in a beech forest, close to several streams. The entrance of the Simina Jama Pit is situated at 920 m a.s.l., the total length of its investigated channels is 270 m, while its depth is 56 m. It starts with a 31-m long vertical passage, which splits into two horizontal channels -left and right (Anđelić et al. 2011). Beetle specimens were found at the end and in the middle of the left horizontal channel with a clay muddy substrate and rocks, on the vertical limestone walls and floor with a high level of humidity (presence of trickling water). The places where the specimens were found in the pit are shown in Fig. 4. It is assumed that the species is actually endogean, as is the case with some other leiodid taxa (e.g., Magdelainella spp.), which inhabit the soil beneath deeply sunken rocks and forest detritus, but can also be found in caves and pits (Pavićević et al. 2012). Pljevlja (northern Montenegro)), is of bathyscioid shape (P. (P.) tarensis sp. nov. is more elongate and of oval shape), it is significantly longer than the new species (TL R 3.0-3.5 mm vs 2.185-2.435 mm in P. (P.) tarensis sp. nov.) and has a quite different shape of aedeagus (stout, with a rounded apex, longer than parameres vs elongate, with a pointed apex, shorter than parameres in P. (P.) tarensis sp. nov.), indicating that these two species are not closely related (Jeannel 1934;Ćurčić et al. 2008a).

Etymology
The species is named after Mt Tara in western Serbia, where its type locality is situated.  (Fig. 5).

Comparisons
Proleonhardella (P.) hirtella, P. (P.) weiratheri and P. (P.) tarensis sp. nov. are somewhat elongate and their aedeagus is narrower than in the remaining congeners, suggesting their specific position within the genus. Based on these features, they are similar to Bozidaria gen. nov., but are much shorter (TL R 1.6-1.8 mm in P. (P.) hirtella, 1.6-2.0 mm in P. (P.) weiratheri and 2.185-2.435 mm in P. (P.) tarensis sp. nov. Proleonhardella (P.) tarensis sp. nov. and its closest relatives (P. (P.) hirtella, P. (P.) weiratheri and P. (P.) neumanni) share the presence of elongate, somewhat convex elytra, which are more than twice as long as the pronotum. Furthermore, the new species, P. (P.) hirtella and P. (P.) weiratheri have a somewhat elongate body shape, while the body shape in the remaining Proleonhardella taxa is more or less bathyscioid. These three species have an elongate aedeagus, contrary to other known congeners, in which the aedeagus is more or less short (Jeannel 1924(Jeannel , 1934. The shape of the aedeagus of P. (P.) neumanni wasn't mentioned in the description of the species or elsewhere (Apfelbeck 1901;Jeannel 1924).

Bionomy, distribution and type locality
The type specimens were gathered using pitfall traps with rotten meat as bait in  in the village of Kaluđerske Bare, as well as in the Sovljačka Pećina Cave in the village of Šljivovica (Fig. 9). Both localities are situated on Mt Tara, near the town of Bajina Bašta, western Serbia. Beetles were found in the inner (from the middle to the innermost point), totally dark parts of the cave sites. The entrance of Pit 4-1-3-27 is situated at 868 m a.s.l., the total length of its investigated channels is 28 m, while its depth is 22 m. After a short vertical passage, the pit opens into a large chamber which contains big rocks at its lowest part. At this point another vertical passage starts, at the end of which is situated a small, moist semicircular chamber with a clay substrate and rocks (Bosco 2016). Beetle specimens were found in the inner part of the larger chamber, among rocks, and in the smaller chamber with a clay substrate and rocks, on the floor and vertical limestone walls with a high level of humidity (presence of trickling water). The entrance of the Sovljačka Pećina Cave is situated at 1080 m a.s.l. and its total length is 43 m (Bosco 2016). The cave is located in a coniferous forest in a valley where the Sovljak stream runs. It is entirely horizontal and consists of a single channel which is oriented to the left. Its height is slightly decreasing towards the end. Beetle individuals were found in the inner  (Reitter, 1911). Light blue sun: P. (Proleonhardella) matzenaueri matzenaueri (Apfelbeck, 1907). Dark blue sun: P. (P.) matzenaueri ottonis Müller, 1917. Purple flower: P. (P.) leonhardi (Breit, 1913). Yellow cross: P. (P.) apfelbecki Jeannel, 1924. Brown circles: P. (P.) remyi Jeannel, 1934. Green squares: P. (P.) hirtella Jeannel, 1934. Pink pentagon: P. (P.) neumanni (Apfelbeck, 1901). Red triangle: P. (P.) weiratheri (Reitter, 1913). Orange rhombuses: P. (P.) tarensis Ćurčić & Pavićević sp. nov. Scale bar = 50 km. part of the cave, on the floor among rocks, both on limestone and clay substrate, where a high level of humidity (presence of trickling water) was evident. Images of the cave localities and the places where the specimens were found in the caves are shown in Figs 7-8. The new species is most probably endogean and is likely to be found outside caves as well -in the deep soil strata and other speleological sites in the surroundings.
Key to the taxa of the genus Proleonhardella Jeannel, 1910(modified after Jeannel 1924 (Figs 9-10)  Fig. 10. Illustrations of morphological characters presented in the Key to the taxa of the genus Proleonhardella Jeannel, 1910(after Jeannel 1924Ćurčić et al. 2008a). A. Short elytra, less than twice as long as pronotum. B. Long elytra, more than twice as long as pronotum. C. Globular antennomere VIII in males. D. Slightly elongate antennomere VIII in males. E. Elytra parallel in basal half. F. Elytra narrowed in basal half.

Discussion
It should be noted that a new genus of leptodirines belonging to the phyletic series of "Leonhardella" was recently established. Ćurčić et al. (2008a) considered the status of P. (P.) remyi and described a new genus, Serboleonhardella S. Ćurčić & Schönmann, 2008, based on this taxon. Numerous differences between P. (P.) remyi and other members of the genus Proleonhardella, some of which are quite significant (body size and form, antennal length, shape of certain antennomeres, form of median lobe and shape of parameral apex), indicated a need to separate P. (P.) remyi as a distinct genus or at least to a specific position within the genus Proleonhardella. This genus was not reported in the catalogues of Perreau (2015) and Hlaváč et al. (2017), nor has it been synonymized so far. Even Jeannel (1934) recognised that P. (P.) remyi is quite remarkable for its large size compared to other congeners, which barely exceed 2 mm in length. The occurrence together of several congeners is a rare phenomenon in caves. Such is the case with P. (P.) remyi and P. (P.) hirtella, which were recorded together at five speleological sites in southwestern Serbia and northern Montenegro (Pavićević et al. 2012). This might also suggest that these taxa are indeed not congeneric. Additionally, Ćurčić et al. (2008a) proposed a new status for Pholeuonillus -as a full genus instead of a subgenus. Interestingly, Pholeuonillus was established by Breit (1913), who gave it generic rank. Later on, Jeannel (1924) treated it as a subgenus of Proleonhardella -a status that was maintained until now. It is recommended to study the taxa in question and other members of the genus Proleonhardella using molecular analyses in order to illuminate their phylogenetic relationships and to have their taxonomic status reconsidered and changed, if needed.
A series of high fluvial plateaus of the Inner Dinarides occur in western and southwestern Serbia (Zlatibor, Jabuka-Babine, etc.). According to their position in the area's relief, these plateaus are presumed to be of Pliocene age (Cvijić 1924(Cvijić , 1926. The palaeokarst in the areas of Mts Povlen and Tara was most probably formed at the same time as the Zlatibor plateau, in the second half of the Pliocene. Based on chronostratigraphic criteria by the International Commission on Stratigraphy (Gibbard et al. 2010;Gaudenyi & Jovanović 2012), it is estimated that the palaeokarst in question is around 3-3.5 Ma old. It is likely that the karstic areas of Mts Povlen and Tara were connected with other karstic regions in their vicinity, favouring links between their subterranean faunas in old geological times, as evidenced by the occurrence of two new endogean and cavernicolous leptodirine taxa and their closest relatives in the surrounding areas.
The tribe Leptodirini has a Palaearctic distribution with its highest diversity located in the Mediterranean (Perreau 2000(Perreau , 2015. It has undergone extensive diversification in the subterranean environment (Ribera et al. 2010). In their comprehensive molecular approach to the phylogeny of western Mediterranean Leptodirini, including the fauna of the Iberian Peninsula, Ribera et al. (2010) revealed that the main subterranean lineages of the tribe were separated before the Early Oligocene.
The Dinaric mountain chain has provided suitable conditions for subterranean life for millions of years, which resulted in the presence of a rich and diverse cave-dwelling fauna (Zagmajster et al. 2008;Kozel et al. 2020;Sendra & Reboleira 2020). The leiodid beetle tribe Leptodirini is among the richest groups in the subterranean habitats (Sket 2005), comprising 175 species and 50 genera, most of which are endemic to the Dinarides. This mountain range is recognized for having the world's greatest species richness of subterranean fauna (Sket 2004;Culver et al. 2006;Deharveng et al. 2012). A very few studies dealing with phylogenetic relationships of certain subtribes within Dinaric Leptodirini exist. These studies were based only on morphology (Jeannel 1930;Perreau & Pavićević 2008;Perreau 2019) and in most cases they have not been tested with molecular data. Only recently, Njunjić et al. (2018) commented on the suprageneric classification of eastern Mediterranean Leptodirini based on molecular phylogeny data. The clade comprising the subtribes Bathysciina Horn, 1880 and Bathysciotina V. Guéorguiev, 1974 was estimated to have originated in the Oligocene (ca 30 Ma ago), while the tested genera of Bathysciina belonging to the phyletic series of "Leonhardella" (Leonhardella and Proleonhardella) separated more recently -in the Miocene (ca 20 Ma ago) (Njunjić et al. 2018).
As in the study of Njunjić et al. (2018) only two taxa belonging to the subtribe Bathysciina (phyletic series of "Leonhardella") were subjected to molecular characterization (Leonhardella (Leonhardellina) antennaria Apfelbeck, 1907 and P. (P.) remyi), more Dinaric genera of Bathysciina should be included in future molecular analyses to establish their phylogenetic relationships and to understand their origin and the colonization of the region by the subterranean representatives of the group. Discoveries of fascinating new genera of Bathysciina in the underground of the Dinaric karst in the last few decades (Nonveiller & Pavićević 1999;Perreau 1999), including the one described herein, suggest that further investigations of the caves of the area are needed.