Pocapharaptinus, Philips and Akotsen

Akotsen-Mensah, Clement & Philips, Keith, 2009, Description of a new genus of spider beetle (Coleoptera: Ptinidae) from South Africa, Zootaxa 2160, pp. 51-67 : 52-54

Pocapharaptinus, Philips and Akotsen , new genus

Type species. Pocapharaptinus müllerae Akotsen and Philips

Diagnosis. The genus is characterized by long erect setae forming four loose tufts dorsally and laterally on the pronotum. The majority of the remaining pronotal surface is densely covered with flocculent, wooly, tan-colored setae that obscures the cuticular surface. When viewed anteriorly, the visible pronotal cuticle medially is triangular in shape. The elytral surface also has distinct puncture rows in addition to rows of recumbent and erect setae.

Description. Body: overall, small to moderate, 1.2–2.8mm long, oval or oblong-oval, convex; light to dark reddish brown. Head: Eyes small, round to somewhat triangular, moderately robust, generally not visible from above; interocular space about 3X eye width; vertex convex, slightly rounded, cavity present beneath eye and laterad of antennal insertion; antennae filiform, 11-segmented, antennal setal length variable from short to long, second antennomere inserted off center of scape near lateral edge, inter-antennal space narrow, with acute carina, slightly to distinctly projecting, more so anterioventrally; clypeus triangular, width ~1/2 head width below eyes; anterior margin of labrum broadly rounded; labial palpi 3-segmented; maxillary palpi 4-segmented; mandibular apex acute, lacking additional tooth; mentum triangular, with cavity. Pronotum: overall, square to slightly elongate; covered with thick spongy or dense setae; two pairs coarse, sub-vertical setal peaks laterally and dorsally, lateral peak elongate, with sparsely spaced coarse setae forming loose tufts, dorsal peak extending posteriorly at middle to near center; cuticle visible, largely devoid of setae both laterally around tufts and anterio-medially to near middle of disc, subtriangular to nearly transverse. Elytra: overall, convex, humeral angles rounded, punctures small, distinct, arranged in 10 rows; punctures sub-equal in size but variable in depth; each elytron with anterior and posterior patch of white setae on all species except P. soutpanensis . Ventral sclerites: Prosternum narrow, elongate, 5X as long as wide, extending onto mesosternum ( Fig. 2 ); mesosternum as long as wide, ~ 1/2 length of metasternum, anteriorly adjacent to procoxae with transversely flattened, rounded projections extending ventrally; metasternum transverse, broadly emarginate posteriorly. Abdominal ventrites with all sutures distinct, 2–5 subequal, 1 and 2 distinctly longer, 4 shortest ( Fig. 3 ). Legs: dorsal and ventral surface of tibiae and tarsi covered with fine recumbent narrow scale-like setae, also with several longer golden-yellow depressed narrow setae; metatarsomere 2X length of pro-and mesotarsomere.

Etymology. Derived from the Greek “poca” (meaning hair or wool), referring to the thick, dense pronotal setae; and “pharan” (meaning cleft or gully), which describes the cleft in the dense pronotal setae. These words are combined with the most speciose ptinid genus name Ptinus .

Comments. Species are concentrated in western and southwestern South Africa ( Fig. 40 ). While species found in western South Africa experience winter rains (June - Sept.) with a long dry season during the summer (Dec. - Mar.), other species in the Western Cape Province are found in regions mainly with a summer rainfall pattern. All taxa are flightless, a characteristic often found in spider beetles that exploit dry dung as a food source in xeric habitats ( Philips 2000). One species has been reared from dry pellets of rock hyrax or dassie ( Procavia capensis [Pallas]), suggesting that dung may be the preferred food source of species in this genus (Philips, unpublished).

Relationships. Philips (2000) noted that precise relationships of most spider beetle genera hypothesized from morphology are obscured due to convergent evolution of features associated with flightlessness, which may be an adaptation for water conservation in a xeric habitat. Many genera superficially look alike and little phylogenetic work has been done to support any purported relationships with the exception of Bellés (1985) and Philips (2000). Hence Pocapharaptinus is one of numerous flightless taxa in southern Africa with unclear affinities. One possible related lineage is southern African Ptinus , as it shares a number of potential synapomorphies with this clade including: a similar cuticular color of pale to dark reddish brown, possession of two white setal patches anteriorly and posteriorly on the elytra, erect and recumbent longitudinal rows of vestiture along and between elytral punctures rows, and similarly shaped elongate legs and antennae.

Distribution and biogeography. Endemic to South Africa, species of Pocapharaptinus are found in a surprisingly wide variety of habitats, including Cape Mountain passes at 2000m elevation, succulent deserts, and coastal scrub ( Fig. 40 ). The distribution of the genus ranges from northern Namaqualand southward to the southwestern Cape Region (between 28˚S and 36˚S latitude) extending eastward to just beyond Mossel Bay (22.41˚E). Species found in the western part of the distribution occur in semi-desert with rainfall <300mm per year ( Kingdon 1989), but with a highly predictable seasonal winter rainfall and moderate temperatures, due in part to the cold Benguela current. Species in the Cape Region exist in the Fynbos, a biome with a unique flora that experiences a climate based on complex interactions between dry cold air from the west and moist warm air from the east ( Kingdon 1989). At Cape Town, occasional rainstorms occur during the summer, with generally increasing frequency towards Mossel Bay in the east. Additionally some sheltered inland areas are relatively hot and dry. Hence, the diversity and complexity of temperature and rainfall patterns is no doubt responsible for the high floristic and faunistic diversity, with many endemic taxa including the species of Pocapharaptinus . Philips and Foster (2004) suggest that the limited distribution of the southern African spider beetle taxa indicate that this greater region is the center of origin for many ptinid species, including those of Pocapharaptinus .

Some species of this new genus have allopatric populations that appear to be separated by geographic barriers. For example, P. acanthos has been collected only near Cape Agulhas and Paarl, two localities in the southwest cape region that are partially separated by mountain ranges. Similarly, P. soutpanensis and P. müllerae are both found north and south of the Olifants River. The populations in each species are morphologically indistinguishable, but there is always the possibility of cryptic species. Alternatively and we think more likely explanations are that the distribution of P. acanthos is due to a collecting artifact, and for the other two species, the Olifants river does not appear to be an insurmountable barrier as one might expect most likely due to periodic lack of river water flow historically ( Harrison et al. 2003). Similar distributions on both sides of this river are also known in other flightless species of beetles including the spider beetle Cryptopeniculus nigrosetus ( Philips & Foster 2004) as well as some species of Scarabaeus (Pachysoma) MacLeay dung beetles ( Harrison et al. 2003).

Figures

FIGURE 40. Known distribution of Pocapharaptinus in the Northern and Western Cape Provinces of South Africa. Open circle, P. m ü l l e r a e; “ B ”, P. harrisoni; closed circle, P. akotsenorum; closed triangle, P. capensis; “ + ”, P. soutpanensis; “ C ”, P. lachnos; “ A ”, P. aboakyer; closed square, P. acanthus.

FIGURES 1 – 4. Pocapharaptinu s, 1. Ventral view of mouth parts; 2. Meso and metasterna and leg bases; 3. Ventrites; 4. Prothorax ventral surface with leg bases and prosternum. Scale bar = 200 µm.