Two new species of the Phanaeus endymion species group (Coleoptera, Scarabaeidae, Scarabaeinae)

Abstract Phanaeus bravoensis sp. n. is described from the coniferous-oak forests in the state of Guerrero, and P. huichol sp. n. from coniferous-oak forests and cloud forests in Jalisco and Nayarit. The new species are closely related to P. halffterorum and P. zoque respectively. Morphological trait combination, geographic distribution, and trophic habits show important differences among the studied species. A distribution map and an updated key to separate the species are included.


Introduction
Phanaeus Macleay, 1819 is a new world genus of dung beetles that presents a bright metallic coloration and a pronounced sexual dimorphism (males with large cephalic horns and striking pronotal projections) (Edmonds 2006). Phanaeus includes at least 55 valid species and 12 species groups. Several studies of Phanaeus have been published in recent years, including major reviews (Edmonds 1994, Arnaud 2002, Edmonds and Zídek 2012. As a consequence, there is a broad knowledge of the geographical distribution of Phanaeus, and it is considered a Neotropical taxon of South American origin. The subgenerus Phanaeus s. str. probably colonized the Mexican Transition Zone during the Miocene, where it diversified and expanded northward into the U.S.A. The subgenus Notiophanaeus, however, radiated and expanded in South America and one species group arrived to the Mexican Transition Zone prior to closure of the Panama land bridge: the endymion species group (Halffter and Morrone 2017).
The Phanaeus endymion species group brings together five closely related Mesoamerican species: Phanaeus endymion Harold, 1863, P. halffterorum Edmonds, 1979, P. pyrois Bates, 1887, P. zapotecus Edmonds, 2006 and P. zoque Halffter, 2017 (Moctezuma and, in addition to the two new species described here. Phanaeus halffterorum was described with 17 individuals from Estado de Mexico and one male from Guerrero. Edmonds (1979) included among the features of P. halffterorum a strong acute tooth in the middle of anterior margin of pronotum (a character present even in the smallest individuals), with the exception of the Guerrero specimen. We studied the P. halffterorum type series and new specimens collected in Guerrero, and we have concluded that the halffterorum population from Guerrero represents a new species, which is described in this work. Phanaeus endymion is a tropical species that appeared to present a disjunct population in temperate forests from the Mexican Pacific slope of the Trans-Mexican Volcanic Belt (Edmonds 1994, Edmonds andZídek 2012). In this study, we also recognize these "endymion" Pacific slope populations as a new species, which is closely related to P. zoque.

Phanaeus halffterorum
Diagnosis. Pronotal granulate sculpturing; major male lacks a tooth in the middle of anterior pronotal margin, pronotal triangle sides curved (Figs 6, 7); sutural margin of each elytron upturned to form a sharp ridge, which is progressively more elevated posteriorly and prolonged into a small, sharp tooth at apical angle; lamella copulatrix as in Fig. 8.
Description. Holotype length 17.8 mm, width at bases of elytra 9.8 mm. Head: Clypeus black with metallic green bright, anterior margin weakly bidentate. Genae metallic green with granular rough sculpturing. Frons with a black cephalic horn, curved posteriorly over pronotum; lateral region of frons is metallic green and weakly rough with no evident punctures. Pronotum: Triangular pronotal disc with lateral fossae and dark metallic green coloring, flattened with lateral undulations. Lateral lines of pronotal disc recurved. Granulate sculpturing without punctuation. Posterior pronotal angles very salient, directed posterolaterally and slightly upturned apically. Basal fossae rounded but weakly impressed. Elytra: Striae fine, black colored, with small but well defined and regularly separated punctures, shagreened rough sculpturing. Interstriae of opaque appearance, dark metallic green coloring, weakly flattened, with shagreened sculpturing, small weakly impressed punctures and transverse roughness more evident on the first three interstriae. Sutural margin of each elytron forms a sharp ridge, which is elevated posteriorly and prolonged into a small tooth at the apical angle. Pygidium: Metallic dark green, glabrous, with weakly impressed small punctures and shagreened rough sculpturing. Protibia: Quadridentate with apical spur. Aedeagus: Similar to that of the P. endymion species group. Lamella copulatrix as Fig. 8.
Variation. Minor male ( Fig. 9): Similar to major male, except the cephalic horn smaller or completely reduced to a frontal carina, posterolateral angles of pronotum reduced to small tubercles located on the central part of pronotum and lesser transverse roughness on the interstriae. The tooth on the elytra sutural margin is reduced. Female ( Fig. 10): As male except head black with green reflections in frons and genae, cephalic carina trituberculate with middle tubercle more elevated, pronotal sculpturing regularly reticular, most of pronotal disk dull black with a well-impressed coarse midline over posterior half of pronotum, pronotal process trituberculate, with the middle tubercle more elevated. Size of paratypes. Mean length 15.5 mm (13.3-17.1 mm), mean width 8 mm (6.8-9 mm).
Etymology. Bravo + ensis. Bravo refers to type locality, Chilpancingo de los Bravo. Remarks. Phanaeus bravoensis is easily distinguished from the closely related P. halffterorum by geographic distribution and morphological characters: P. bravoensis major male lacks a tooth in the middle of anterior pronotal margin and its pronotal triangle sides are curved (Figs 6, 7), whereas these are straight on P. halffterorum (Figs 1, 2). Differences are observed between the lamella copulatrix (more developed left lobe in P. halffterorum, strongly developed central ridge and right lobe in P. bravoensis; Figs 3, 8) and shape of female pronotum. In P. bravoensis mayor female    pronotal midline is stronger impressed; pronotal tubercles are located in similar position and of equal size in P. halffterorum, while pronotal central tubercle is in anterior position and bigger than lateral tubercles in P. bravoensis (Figs 4, 10).
Description. Holotype length 17.6 mm, width at base of elytra 9.8 mm. Head: Clypeus dark brown with bright metallic green, anterior margin bidentate. Genae metallic green with granular sculpturing. Frons with a black cephalic horn, curved posteriorly over pronotum; lateral region of frons is metallic green weakly rough with coarse and weakly impressed punctures. Pronotum: Triangular pronotal disc with lateral fossae and metallic olive green coloring, flattened with lateral undulations. Lateral lines of pronotal disc not impressed. Sculpturing shagreened without punctures. Anterior pronotal angles wide and rounded. Posterior pronotal angles sa-  lient, directed laterally and weakly upturned apically. Basal fossae weakly impressed. Two lateral carinas are impressed near to pronotal apex. Elytra: Striae black-green colored, shagreened with small well-spaced punctures and weakly rough sculpturing. Interstriae strongly impressed with small punctures. Pygidium: Metallic olive green, with well-impressed punctures and shagreened rough sculpturing. Protibia: Quadridentate with apical spur. Aedeagus: Similar to that of P. endymion species group. Lamella copulatrix as Fig 12. Variation. This species shows variation in color, being olive green or dark green with blue reflections. Minor male (Fig. 13): Similar to major male, except the cephalic horn smaller and the posterolateral angles of pronotum reduced. Female (Figs 14, 15):  As male except head black with green reflections in frons and genae, cephalic carina trituberculate, pronotal sculpturing shagreened, most of pronotal disk dull black, pronotal process trituberculate. Size of paratypes. Mean length 17.5 mm (16-18.7 mm), mean width 9.4 mm (8.7-9.8 mm).
Etymology. The name of the new species refers to the Huichol ethnic group, which inhabits part of the geographic region where the type series was collected.
Remarks. Phanaeus huichol is easily distinguished from the closely related P. zoque by its geographic distribution and morphological characters: Phanaeus huichol male shows two elongate and weak tumescences near to pronotal apex, while P. zoque presents two strong tubercles; the anterior lateral angles of the pronotum  of P. huichol are wider and more rounded than those of P. zoque. Major females of P. huichol show tridentate pronotal projections with teeth of similar size (Fig. 15), while in the P. zoque major female the middle dent resembles a carina, with smaller lateral teeth. In both males and females of P. huichol the anterior metasternal angle is obtuse in lateral view (Fig. 16), whereas in P. zoque this is almost right-angled but with a rounded apex (Fig. 17). Anterior metasternal angles are notably less angular in P. huichol (Fig. 18), while they are more evident in P. zoque (Fig. 19). Differences in angulation are also evident in other ventral sternites (lateral mesometasternal angles evanescent in P. huichol, those angles well defined and slightly curved in P. zoque). Phanaeus huichol is restricted to the Pacific slope of Mexico (Jalisco and Nayarit), while P. zoque is found in the Mexican southeast (Oaxaca and Chiapas).
Type locality. MEXICO, Jalisco, Mazamitla. Distribution and Ecology. This species occurs in the Sierra Occidental of Jalisco and the Sierra del Nayar (Nayarit), in coniferous-oak forests, cloud forests and riparian forests, between 700-1760 m a.s.l. This species seems to be generalist, since specimens have been collected with carrion, dung and fungus.

Key to the Phanaeus endymion species group (modified from Edmonds and Zídek 2012 and Moctezuma and Halffter 2017).
1 Sutural margin of each elytron upturned to form a sharp ridge, which is progressively more elevated posteriorly and prolonged into a small, sharp tooth at apical angle; elytral margin slightly excised adjacent to this tooth . Major male with a tooth in the middle of anterior pronotal margin, pronotal triangle sides straight (Figs 1, 2). Lamella copulatrix as in Fig. 3. Elytral interstriae distinctly flattened and uniformly dull (more convex and shiny in some Central American populations); striae not strongly impressed basally, anterior ends in most specimens bearing deep punctures rather than large fossae. Male: Pronotal disk dull, velvety smooth medially, finely asperate, brighter laterally. Female: Pronotum evenly convex, lacking anteromedial concavity even in largest specimens, bearing three round, smooth tubercles in transverse line near anterior margin. Head and pronotum largely highly shiny metallic red to nearly completely dull black with metallic red restricted to ridges and isolated areas on anterior part of pronotum; elytra dull to weakly shiny black; pygidium usually metallic red medially, green peripherally, in some completely red or green. Dorsum dark blue or shiny green; in few specimens shiny green with strong yellow reflections. Anterior margin of pronotum projected forwards. Relatively rounded posterolateral angles of pronotum. Internal sack of aedeagus and lamella copulatrix as in Moctezuma and Halffter (2017;Fig. 16 Anterior metasternal angle obtuse in lateral view (Fig. 17). Lateral metasternal angles well defined and slightly curved (Fig. 19). Few specimens olive green with golden/reddish reflections. Internal sack of aedeagus and lamella copulatrix as in Moctezuma and Halffter (2017;Fig. 15 Anterior metasternal angle almost right angled but with rounded apex in lateral view (Fig. 16). Lateral metasternal angles evanescent (Fig. 18). Lamella copulatrix as in Fig. 12

Discussion
Notwithstanding the fact that a review and new key are required for the endymion species group, we have found no reason to delay publication of this new species. We do not include a new key to separate the endymion species group. As an alternative, however, we modified the keys presented by former studies Zídek 2012, Moctezuma and. We also considered species distribution, ecology, and trophic preferences as additional criteria to separate the new species. Phanaeus bravoensis and P. halffterorum exhibit unique combinations of character states in the external morphology and in the sclerites of the internal sack of the aedeagus, and these character combinations are sufficient to consider them as distinct species (Wheeler and Platnick 2000). Phanaeus bravoensis and P. halffterorum seem to be closely related species, because of similarity in the granular pronotal microsculpture, pronotum shape and the apical tooth in the base of the elytra.
Phanaeus bravoensis and P. halffterorum occupy distinct ecological niches. They both inhabit coniferous-oak forests, but P. halffterorum is a mycetophagous specialist while P. bravoensis is attracted to dung and carrion (Edmonds 1979, 1994, 2003, Deloya et al. 2014). Both species are geographically isolated and endemic to small montane areas. Phanaeus bravoensis is restricted to the Sierra Madre del Sur (750-2150 m. a.s.l.) in the surroundings of Chilpancingo de Los Bravo, while P. halffterorum has been reported from the mid highlands of the central region of the Trans-Mexican Volcanic Belt (2200-2360 m. a.s.l.), in the surroundings of Temascaltepec. Arnaud (2002) mentioned that P. halffterorum is located in the "Federal District", but this location is doubtful and the name could have been confused with State of Mexico (Estado de México). Climatic conditions where these species are found differ, being tropical or sub-tropical for P. bravensis and temperate for P. halffterorum. Lizardo et al. (in press) states that potential distribution modeling of species could not be performed using localities of P. halffterorum from the State of Mexico and Guerrero simultaneously, probably because of the lack of information and/or taxonomical/geographical errors. We agree with the view of Lizardo et al. (in press) and have therefore included additional localities and corrected the taxonomical issue that involved P. halffterorum.
Vicariance is likely the process that led the radiation of P. bravoensis and P. halffterorum. Aridification of the Balsas Valley during the Pleistocene could have isolated the populations of a common ancestor (Edmonds 1994). This hypothesis considers a relatively recent origin of this species within the endymion species group. We consider the possibility that P. bravoensis, P. halffterorum and P. zapotecus represent a phyletic line within the endymion species group, characterized by the presence of a granular pronotal microsculpture. Molecular phylogenetic studies are required to confirm or refute our hypothesis on the vicariant origin of P. bravoensis, the geological period of divergence and the existence of the lineage bravoensis-halffterorum-zapotecus.
Phanaeus huichol has been traditionally confused with P. endymion, a noteworthy fact considering the number of important reviews that have been published in recent years (Edmonds 1994, Arnaud 2002, Edmonds and Zídek 2012. Species potential distribution modeling clearly demonstrates a geographical segregation among P. huichol, P. endymion and P. zoque (Lizardo et al. in press). This new species seems to be closely related to the recently described P. zoque in size, coloring and habitat preference, but there are clear differences in external and genital morphology. On the other hand, an important disjunction exists between the distributions of both species: they are separated by ≈900 km of distance, including the presence of important biogeographic barriers (i.e., the Tehuantepec Isthmus, the Sierra Madre del Sur and the Balsas Valley). Phanaeus huichol could represent a relatively ancient colonization by the P. endymion species group in the Central Pacific region of Mexico, that drove a later isolation of this species in the westernmost areas of the Trans-Mexican Volcanic Belt.
While both species prefer pine-oak forests, P. huichol also inhabits cloud forests, while P. zoque has not been collected despite intensive sampling effort in cloud forests of Los Chimalapas (Moctezuma and Halffter 2017). Trophic habits of P. huichol are well known, being a generalist species attracted to different kinds of dung, carrion, and fungus, while P. zoque has been collected only on dung (Quiroz-Rocha et al. 2008, Moctezuma and. Feeding habits of P. huichol could be related to xeric conditions during dry season, when dung becomes an extremely ephemeral resource that rapidly loses humidity and dietary quality, and additional food sources are required Edmonds 1982, Moctezuma et al. 2016). Elevation tolerance of these species seems to overlap and they are endemic to montane areas, although the altitudinal range of P. huichol is greater: P. huichol is found between 700-1760 m. a.s.l., while P. zoque inhabits between 918-1325 m. a.s.l.