Revision of the rhinoceros beetle genus Oryctophileurus Kolbe with description of a new species, the male of O. varicosus Prell, and notes on biogeography (Scarabaeoidea, Dynastinae, Phileurini)

Abstract The genus Oryctophileurus is reviewed and its validity is supported by a combination of the following apomorphic characters: a single cephalic horn with lateral carina, pronotal cavity with ocellate punctures and two teeth or tubercles close behind the anterior pronotal margin. The male of Oryctophileurus varicosus Prell, 1934, is described for the first time. A new species, Oryctophileurus guerrai Perger & Grossi sp. n., from subhumid Tucuman-Bolivian forest in the Southern Bolivian Andes is described. The new species is distinguished from its closest relative, O. armicollis Prell, 1911, by a narrower distance between the inner teeth of the dorsal pronotal protuberances and a reduced area of weakly developed ocellate punctures above the posterolateral pronotal margin. The occurrence of Oryctophileurus species in areas of endemism along the eastern slope of the tropical Andes suggests that these populations represent biogeographic “relicts”, and the discovery of Oryctophileurus guerrai sp. n. in the southern Bolivian Andes suggests that this area is underrated with respect to insect diversity and endemism.


Introduction
The evolution of exaggerated morphological traits such as cephalic and pronotal horns in male rhinoceros beetles (Dynastinae) has been of interest to biologists for centuries (Rowland and Miller 2012). The Neotropical genera Oryctophileurus Kolbe, 1910, andAmblyodus Westwood, 1878, belong to the few taxa that lack pronounced gender dimorphism: although less developed, the females bear cephalic horns as well (Grossi and Grossi 2011). However, despite this exceptional feature, both taxa are rarely treated in the scientific literature, presumably because of the difficult accessibility of their forest habitats or a cryptic way of life.
Oryctophileurus was established by Kolbe (1910) to stabilize the generic taxonomy of Phileurus nasicornis Burmeister, 1847, a species recorded from Colombia. Prell (1911) described a second species, O. armicollis, from Peru based on two males. The third species of the genus, O. varicosus, was described from a female only without locality record (Prell 1934). Subsequent literature on the taxonomy of Oryctophileurus is restricted to redescriptions of the type specimens by Endrödi (1977Endrödi ( , 1985 and a cladistic analysis of Phileurini that included O. armicollis and O. varicosus (Ide 1998). Ide (1998) recognized a noticeable similarity between Oryctophileurus and Amblyodus, and Grossi and Grossi (2011) subsequently suggested synonymizing Oryctophileurus with the latter. However, the taxonomic position of Oryctophileurus has not been revised so far.
The purpose of this contribution is to stabilize the taxonomy of this group through the careful examination of all species originally described in Oryctophileurus and Amblyo-dus. A new species of Oryctophileurus from the southern Bolivian Andes and the male of Oryctophileurus varicosus are described the first time, and their biogeography is reviewed and briefly discussed.
Additional specimens were collected during a biodiversity survey headed by the first author in the southern Bolivian Andes, in the northwestern buffer zone of the Tariquía Flora and Fauna National Reserve, department of Tarija, Bolivia. Several transects of about 6 km of subandine, subhumid, semi-deciduous Tucuman-Bolivian forest (Navarro and Ferreira 2011) were surveyed from November to December 2010. The study area and transect images were obtained from Google Earth 2012 and Landsat imagery courtesy of NASA Goddard Space Flight Center and the U.S. Geological Survey ( Fig. 1A-C). Collected specimens are deposited in the Colección Boliviana de Fauna (La Paz, Bolivia) (CBF).
Morphological characters were examined with a stereomicroscope, and specimens were sexed via genital dissection. Morphometric measurements were taken with a digital caliper. Body length was measured from the apex of the clypeus to the apex of the pygidium.
A map (Fig. 1A) with the known distribution of treated taxa is included to facilitate the interpretation of biogeographical relationships. Distributional data from the literature is only considered when based on properly identified specimens. Records of Oryctophileurus species from Central America (Endrödi 1977;Lachaume 1992) need to be confirmed and are not considered here.
Species of Oryctophileurus are distinguished from other Phileurini by a combination of the following apomorphic characters: a single cephalic horn with lateral carina, pronotal cavity with ocellate punctures and two teeth or tubercles close to the anterior pronotal margin, teeth vertically positioned at about the same level as the outer eye margins.
Taxonomy and discussion. The following characters were cited by Endrödi (1985) for Oryctophileurus, Amblyodus, Microphileurus Kolbe, Metaphileurus Kolbe, Trioplus Burmeister, and Goniophileurus Kolbe and are here not considered as generic: outer side of mandible tridentate; antenna 10-jointed; elytra with punctate rows; proleg sexually monomorphic, protarsus not thickened in male. Oryctophileurus and Amblyodus are distinguished from the other mentioned genera by large horns, a distinctly developed and posteriorly carinate pronotal cavity and four external teeth on the protibia (Endrödi 1985;Ide 1998). However, in Amblyodus the two cephalic horns lack the lateral carina, the punctures in the pronotal cavity are predominately fused to short, transverse ridges, and the teeth close to the anterior pronotal margin are absent. Except for the horn number, these generic differences between Oryctophileurus and Amblyodus have not been recognized by previous workers. Based on the combination of apomorphic characters of Oryctophileurus that lacks in Amblyodus we suggest retaining the genus Oryctophileurus. Pronotal protuberance more strongly developed in males than females of the similar size. Elytral striae and interstitial punctures arranged in regular lines .. 3 3

Key to species of Oryctophileurus
Distance between inner teeth of dorsal pronotal protuberance in male wider than width between eyes ( -Distance between inner teeth of dorsal pronotal protuberance in male as wide as width between eyes (Fig 7B), in females separated by a small fissure only (Fig. 8C). Anterior pronotal concavity accounts for about 30% of the dorsal pronotal surface in males. Area of ocellate punctures above posteriolateral pronotal margin reduced laterally (Fig. 7D Diagnosis. Color dark brown, moderately shining. Horn on frons not projecting above anterior edges of pronotal protuberance, weakly recurved, in female with truncate apex; ocular canthus rounded in male, and subquadrate in female. Pronotum broadly rounded, more in female. Distance between inner teeth of dorsal pronotal protuberance narrower than distance between eyes. Pronotal protuberance on same level with elytra. Development of horn and pronotal protuberance equal in both sexes. Elytra striate, with five well defined discal striae; striae regular, at sides weakly defined; punctures regular, about the same size of those at disc. Meso and metatibiae with 4 to 5 distal teeth. Pygidium regularly convex in both sexes, more in female, and densely and finely wrinkled. Parameres with basal half broad, apex slender, straight.
Geographical distribution. The species is known only from the Cauca Valley in Colombia, which is surrounded by the parallel, peninsula-like projections of the Andean Cordillera Occidental and Cordillera Central and the Muzo municipality which is situated on the eastern slope of the Cordillera Oriental (Fig. 1A). These areas include wet premontane forest and, to a lesser extent, upper montane forests and paramos (Espinal 1992   cylindrical horn with narrow apex; each side of horn with elongated, weak carina, anterior surface with slightly concave furrow, furrow reaching apex. Mandible tridentate, teeth upturned. Mentum with longitudinal furrow wider anteriorly and posterior concavity narrow with subparallel sides. Pronotum. Shape subquadrate, narrower than elytra together. Discal area covered by ocellate punctures combined with C-shaped, coalescent punctures; discal surface flat and declivous anteriorly (Fig. 4A, B); anterior and lateral margins complete with a marginal bead, concave at middle; posterior marginal bead absent. Pronotal disc carinate, carina convex, smooth; anterior carina more pronounced; near anterior border with a conspicuous tubercle present in each anterolateral corner; posterior carina joined posteriorly on pronotal margin, bisinuous. Anterior angle acute, posterior rounded. Middle apex laterally with smooth convex carina, intercalated by rugose area and coarse punctures. Prosternal process long, trapezoidal, concave at base and posteriorly produced; base with a spine like posterior process.
Elytra. Striae irregular, and not defined, even laterally; punctures ocellate, irregular, larger on discal area and becoming smaller laterally and posteriorly; elytral apices densely punctate, punctures small to moderate; apical umbone convex, smooth. Scutellum triangular, densely punctate; punctures ocellate, moderate in size. Pygidium. In lateral view widely convex; surface totally punctate; punctures smaller and denser near anterior margin and sides, sparser and larger to apex; apex with marginal bead.
Remarks. The records cited here are the only known specimens. Endrödi (1977) described the holotype as a male possibly based upon the fact that it has a horn. Endrödi (1985) correctly redescribed the type specimen as a female, indicating that the male was unknown as was pointed out in the original description by Prell (1934). Ide (1998) cited a male specimen from Rios Pichis & Perene, Peru, which was, however, not described. We describe here the male of O. varicosus for the first time. Diagnosis. Color black, strongly shining. Head anteriorly flat, not concave; canthus subquadrate, in some specimens weakly projected forward; horn in males strongly recurved, on about the same level or slightly higher than posterior pronotal protuberance. Mentum with longitudinal furrow flat and wide, as well as posterior margin. Distance between inner teeth of dorsal pronotal protuberance in male wider that width between eyes (Fig. 6A); in females separated by a concavity with occelate punctures; pronotal concavity accounts for about 40-50 % of dorsal pronotal surface in males. Ocellate punctures above posterior-lateral pronotal margin continuous (Fig. 7C). Each elytron with 10 striae; punctures ocellate, sometimes coalescent and elongated, decreasing in size to sides; interstriae smooth, convex. Striae and interstitial punctures arranged in regular lines Mesotibia with 3 to 5 apical teeth; metatibia with 4 to 6 apical teeth. Pygidium in males distinctly more convex than in females, moderately punctate, denser at base and sides. Aedeagus symmetric (Fig. 5A); parameres with apex rounded to subtriangle shaped (Fig. 5B).

Oryctophileurus armicollis
Geographical distribution. Oryctophileurus armicollis is known from Peru (Prell 1911; location not specified) and the Andean (Nor Yungas, La Paz dep.) and Subandean (Cosincho, Beni dep.) areas of Bolivia (Fig. 1A). The ecosystem between 800 and 2000 m a.s.l. in this area is considered as South Yungas submontane, subhumid forest (Josse et al. 2003) and receives an annual precipitation between 1500-6000 mm (Ibisch et al. 2003a). The locality data suggests that this species is closely associated with the Bolivian Yungas forest and might also occur in the Peruvian Yungas forest.

Diagnosis.
Oryctophileurus guerrai sp. n. is distinguished from the morphologically similar O. armicollis by the distance between the inner teeth on the dorsal pronotal protuberance (in males as wide as width between eyes) (Figs 7B, 8A) and in females by the inner teeth separated by only a small fissure (Fig. 8C). In smaller males (body length 18.5 mm) of O. armicollis the distance between the inner teeth of the pronotal protuberance is wider than the width between the eyes and in larger males (body length 20 mm) as wide as the distance between the outer eye margins (Fig. 6A). In females of O. armicollis the inner teeth of the pronotal protuberance are separated by a comparably wide, continuous, parallel concavity containing ocellate punctures (Fig. 6C).
In both sexes of O. guerrai the ocellate punctures above the posteriolateral pronotal margin are smaller, shallower and sparser than in O. armicollis and the area of ocellate punctures above posteriolateral pronotal margin is reduced laterally (Figs 7D; 8B, D). In both sexes of other Oryctophileurus species the pronotum posteriolaterally has a continuous area of distinctly developed, ocellate punctures.
In the male O. guerrai the pronotal protuberance is dorsally higher and the cephalic horn longer (Fig. 8B) than in similar-sized O. armicollis (Fig. 6B) and O. nasicornis (Fig. 3B). In O. nasicornis, both characters are less produced. In the male of O. varicosus (Fig. 4B), with its slightly larger body, the pronotum is much flatter than in the male of O. guerrai.
Pronotum (Figs 7B, D; 8A, B). Shape subtrapezoidal, evenly rounded laterally, smooth, with 2 impressions posteriolaterally; posterior edges slightly obtuse. Basal half smooth, longitudinally ridged, dorsally bulging until transverse median carina, with 2 dorsolateral, coarsely punctate concavities on both sides; transverse median carina with 4 obtuse teeth, 2 inner teeth dorsally with small concavity, distance between inner teeth of dorsal pronotal protuberance as wide as width between eyes; anterior half of pronotum strongly concave, with ocellate punctures, 2 obtuse teeth close to anterior pronotal border, teeth at same level with lateral eye margins when seen from dorsal and lateral views. Prosternal process trapezoidal, concave at the base, posteriorly produced; base with spine-like process posteriorly.
Legs. Protibia with 4 teeth, basal tooth weakly developed. Meta-and mesotibia apically with 3 broaden, shovel-shaped teeth, each tooth additionally furnished with small, apical teeth. The specimen was found dead with damaged abdomen, soft parts and genitalia missing.
Female allotype (Figs 8C,D). Similar to male except by the following features: body length 19 mm, width 8.2 mm; head with cephalic horn less developed, reaching only dorsal pronotal protuberances when seen in lateral view; pronotum longer than high, dorsal longitudinal pronotal concavity about as narrow as width of cephalic horn, uppermost teeth of dorsal pronotal protuberances obtuse, separated by a small fissure.
Derivation of specific epithet. The species is named after our friend and colleague, Fernando "Fideo" Guerra, for his lifetime commitment to the investigation of the Bolivian fauna. His participation in the actual survey in the southern Bolivian Andes has led to the discovery and description of several previously unknown taxa (e.g., Perger and Guerra 2012), and he was also the first to collect an individual of Oryctophileurus guerrai, sp. n.
Geographical and ecological distribution. O. guerrai is known only from the northwestern area of Tariquía National Reserve (Tarija department) in the southern Bolivian Andes (Fig. 1). The forest in the this area is considered subandine subhumid, semi-deciduous, Tucuman-Bolivian forest (TBF) (Navarro and Ferreira 2011) with a mean annual temperature of 18.7 °C and an annual rainfall of 1334 mm (SENAMHI 2007). Oryctophileurus guerrai is likely endemic to TBF (see discussion below) and might also occur in the northern limit (Santa Cruz department) and the Argentinean portion of this forest type (Jujuy, Salta and Tucuman departments).
The two individuals of the new species were collected in a narrow valley (elevation 1008 m a.s.l.) (Fig. 1C). The female was observed during the day on the floor of the densely vegetated, moist gully (Figs 1C, D). The male was found dead in a similar habitat. No individuals of the species were observed in subhumid forest along the slopes and during eight nights of sampling with a light trap close to the collection area. Like the other species of this genus, which are only known from few individuals, O. guerrai might be rare or has a cryptic way of life.
Remarks. As in males of other dynastine taxa with exaggerated secondary sexual traits (e.g., Eberhard 1979;Rowland 2003), the cephalic horn and pronotal structures of O. armicollis males (and likely in the males of other Oryctophileurus species) vary allometrically. Larger males have larger horns and pronotal armature with respect to their body length. Accordingly, such characters should be compared in specimens having a similar size. Nevertheless, the distance between the inner pronotal protuberance teeth appears to be positively allometric in O. armicollis, since it is wider in larger males (body length 20 mm) than in smaller males (body length 18.5 mm). In the male (body length 20 mm) of O. guerrai the inner pronotal protuberance teeth are separated by a gap (Fig. 6B) that is narrower than in the smaller male of O. armicollis (body length 18.5 mm), indicating that the ratio of body length/ pronotal protuberance teeth distance is never overlapping inter-specifically between similar-sized individuals.

Biogeographical affinities
While the two Amblyodus species occur in Amazon lowland forest (A. castroi Grossi & Grossi) and Central American mountain forests (A. taurus Westwood) (Grossi and Grossi 2011), the known distributional pattern suggests that the species of Oryctophileurus are closely associated with forest habitat in the Andean area (Fig. 1).
As proposed for other Andean taxa (see Hoorn et al. 2010 andRull 2011 for reviews), the diversification of Oryctophileurus might be related to the creation of heterogeneous edaphic mosaics and dispersal barriers by the uplifting of the Andes in the mid-Miocene, marine incursions into the Amazon basin, and the subsequent quaternary climatic cycling. High diversity and endemism in the Andean area are further explained by climatic stability due to orographic rain barriers and lower extinction rates during periods of drastic climatic changes (Fjeldså et al. 1999). The collection locations of Oryctophileurus species along the eastern slope of the tropical Andes correspond with peak concentrations of endemics (see Swenson et al. 2012;WWF 2012), suggesting that Oryctophileurus species represent biogeographic relicts that persisted during periods of ecological change.

Oryctophileurus in the Southern Bolivian Andes
The discovery of O. guerrai extends the known distributional range of the genus more than 600 km southwards. In view of the mainly tropical Andes distribution of Oryctophileurus species, the presence of this genus in the southern Bolivian Andes, close to the Argentinean border, is surprising. Because of a change in orientation of the mountain ranges at the elbow of the Andes and local topographic features, the TBF is distinguished from Bolivian Yungas forest (BYF) by a more pronounced and prolonged dry season, occasionally accompanied by frost periods (Fjeldså et al. 1999), and less annual precipitation and humidity (Ibisch et al. 2003a;Killeen et al. 2007). Corresponding with a general decrease in biodiversity (Schulenberg and Awbrey 1997;Ibisch et al. 2003b;Churchill and Lozano 2009), several scarabaeoid genera such as Dynastes Kirby, Sphaenognathus Buquet, Scortizus Westwood, and Cantharolethrus Thomson, meet their southern distributional limit at the elbow of the Andes (see Paulsen 2010 for distributional maps).
Nevertheless, the discovery of Oryctophileurus guerrai and other endemic TBF representatives of butterfly genera Blandin and Gareca 2011) and tiger beetle genera (Perger and Guerra 2012) with diversity center in the northern tropical Andes suggests that the assumed decrease in species richness in some groups is the result of sampling bias and the TBF belongs to the important areas of insect endemism along the eastern slope of the Andes.
This hypothesis should be tested in further studies because human impact and low protection status of such ecoregion (see Schulenberg and Awbrey 1997;Ibisch et al. 2003a) might not only threat already known but also many undiscovered endemics with extinction.