Description of a new species of Sternocoelis from Morocco with proposal of the Sternocoelis marseulii species group (Coleoptera, Histeridae)

Abstract TheSternocoelis marseulii species group is proposed based on antennal and prosternal characters. Five species are included in the group:Sternocoelis marseulii (Brisout de Barneville, 1866)(Spain), Sternocoelis viaticus Lewis, 1892 (Algeria), Sternocoelis vaucheri Lewis, 1896 (Morocco), Sternocoelis berberus Lackner & Yélamos, 2001 (Morocco)and Sternocoelis yelamosi sp. n. (Morocco). The external morphology of Sternocoelis yelamosi sp. n. is described and illustrated, the illustrations of genitalia of all species of the group (except for Sternocoelis vaucheri) are provided and a key to the species of the group is given.


Introduction
The genus Sternocoelis Lewis, 1888 is a small genus of myrmecophilous histerids with 27 described species distributed in the Mediterranean area with most species described from Morocco and Algeria (Yélamos 1995, Mazur 1997. The genus has been recently revised by Yélamos (1995). Since then only one further species has been described, from the Moroccan High Atlas (Lackner and Yélamos 2001). Recently, mainly Slovak and Czech coleopterists have carried out numerous expeditions with focus on the myrmecophilous beetles of Morocco. The newly described species from the Moroccan Middle Atlas results from one such expedition and shows that our knowledge of the Moroccan fauna of Sternocoelis is still incomplete.

Material and methods
Beetles, after being removed from original cards, were side-mounted on triangular points and examined under Nikon 102 binocular microscope with diffuse light. Male genitalia were first macerated in 10% KOH solution for about 15 minutes, cleared in 80% alcohol and macerated in lactic acid with fuchsine heated up to 60°C for another two hours. After that, they were treated with aceto-salycilate heated up to 60°C for 15 minutes and cleared in xylene. They were subsequently examined in α-terpineol in a small dish. Digital photographs were taken by a Nikon 4500 Coolpix camera and edited in Adobe Photoshop CS3. Based on the photographs, observing the actual genitalia, pencil art was drawn; pen art followed, re-tracing the pencil art and making minor corrections. SEM photographs were taken by Hitachi S-2250N camera.
The following acronyms of museums and private collections are used throughout the text:

Abbreviations
Abbreviations of morphological measurements follow Ôhara (1994) and are used throughout the text as follows:

APW
width between anterior angles of pronotum EL length of elytron along elytral suture EW maximum width between outer margins of elytra PEL length between anterior angles of pronotum and apices of elytra PPW width between posterior angles of pronotum.
Separate lines of the same label are marked by slash (/); separate labels are marked by double slash (//). Morphological conventions and terminology and methods of illustration preparation follow Lackner (2010).

Sternocoelis marseulii species group
All members of the group can easily be distinguished from all other Sternocoelis by the combination of the following character states: 1. prosternal lobe at the same level or slightly below the level of prosternal keel; 2. prosternal lobe not divided medially and without deep emargination; 3. prosternal keel with carinal prosternal striae distinct and (almost) joined anteriorly; 4. elytra with first dorsal elytral stria complete; 5. antennal scape with a 'hook' (except for S. viaticus). Yélamos (1995), in his revision of the genus placed species S. marseulii (Brisout de Barneville, 1866), S. vaucheri Lewis, 1896 and S. viaticus Lewis, 1892 in a small clade closest to the out-group (Haeterius ferrugineus (Olivier, 1789)). Sternocoelis berberus Lackner & Yélamos, 2001 and S. yelamosi (described here) share with the three afore-mentioned species identical character states, so we believe that these two species also belong in this plesiotypic clade, which we define as 'Sternocoelis marseulii species group'. Although the monophyly of this group is highly likely, it requires testing by a phylogenetic analysis in the future. A phylogenetic analysis of Sternocoelis would be, however, outside of the scope of this paper. We are aware of the fact that proposing new taxonomic structure without a real phylogenetic analysis to support it should not be a standard measure. In the present work we therefore designate this species-group mostly on pragmatic grounds as an informal taxonomic unit that should serve as a pointer for the future studies of this difficult genus. We believe that male terminalia should be examined in all extant species with the special focus on the male terminalia and spiculum gastrale in particular (see Discussion). All five species included in the group are externally rather similar and, for secure identification, the examination of the male terminalia, especially spiculum gastrale, is necessary.
Pronotum with dense fine punctulation anteriorly and evanescent punctulation laterally and basally, with sparse setae (many setae probably worn off); pronotal sides weakly separated from disc by shallow marginal depression; marginal pronotal stria present on basal three-quarters; anterior pronotal angles produced, truncate; posterior angles of pronotum acute, not produced.
Propygidium about 2.5 times as long as pygidium, both with sparse punctulation and sparse long setae.

Discussion
S. yelamosi shares numerous character states with another four species (S. vaucheri, S. berberus, S. viaticus and S. marseulii) that are found in Morocco, Algeria and Spain, respectively. Most of these character states, according to the phylogenetic analysis performed by Yélamos (1995), are presumed to be symplesiomorphies (Yélamos 1995:168). Yélamos (1995) determined polarities of character states using the Palaearctic genus Haeterius Dejean, 1833 for the out-group. Yélamos (1995) did not study male terminalia in detail; he only mentioned that "...male genitalia are very constant, with an almost imperceptible intraspecific variability" (Yélamos 1995: 168). According to our study of the male terminalia of members of the 'Sternocoelis marseulii species group' the most reliable character for distinguishing species of this group is the shape of spiculum gastrale, especially its apical and basal ends (compare Figs 13,26,37 and 45). S. marseulii is the only species of S. marseulii species group that already had its spiculum gastrale illustrated (Yélamos 1995: 147, Fig. 84). However, our study of the male terminalia of S. marseulii indicates that the spiculum gastrale of this species (Fig. 26) is rather different from that illustrated by Yélamos (1995). The rest of the male terminalia (14)(15)(16)(21)(22)(23)(24)(25)(27)(28)(29)(32)(33)(34)(35)(36)(38)(39)(40)(41)(42)(43)(44)(46)(47)(48) show more uniformity and are less valuable tools for the intra-specific recognition. The spiculum gastrale of S. vaucheri could not have been examined; therefore the validity of this taxon remains dubious. S. vaucheri is known only from two males and two specimens of unidentified sex, all collected more than hundred years ago in Tangier (northern Morocco). Two males of this species belonging to the type series housed in BMNH have been examined, unfortunately their male terminalia (except for the aedeagus already drawn by Yélamos 1995) are damaged and unsuitable for drawing. According to Yélamos (1995), there should be another two specimens of unidentified sex housed in MNHN; these two specimens, however, have not been found in the col- lections (Taghavian pers. comm., 2011). A lot of effort was devoted to find this rare species in the surroundings of Tangier, Morocco, but without success. According to Yélamos (pers. comm. 2011), S. vaucheri might be a junior synonymy of S. marseulii. S. marseulii occurs predominantly in the mountains of central and eastern Spain, with few findings also in southern Spain (Yélamos 1995). One locality, Sierra de Córdoba is approximately 300 km from the type locality of S. vaucheri (Tangier, Morocco). However, without the examination of the male terminalia of S. vaucheri it would be premature to synonymize the two species and therefore both species are kept in their current taxonomic status. We believe that a newly performed phylogenetic analysis including the male terminalia, with desired molecular characters would help to elucidate the relationships among the Sternocoelis species.