Ptomaphagus parashant Peck and Wynne

Peck, Stewart B. & Wynne, J. Judson, 2013, Ptomaphagus Parashant Peck And Wynne, New Species (Coleoptera: Leiodidae: Cholevinae: Ptomaphagini): The Most Troglomorphic Cholevine Beetle Known From Western North America, The Coleopterists Bulletin 67 (3), pp. 309-317 : 311-315

Ptomaphagus parashant Peck and Wynne , new species

( Figs. 2–4 )

Type Specimens. Holotype female and allotype male deposited in Canadian Museum of Nature ( CMN), Ottawa , Canada. Type locality: USA, Arizona, Mohave County, Parashant National Monument , PARA-1001 cave, N36°39′, W113°37′. Type label data: female holotype; 2.ix.2011, J.J. Wynne, sweet potato bait #4, site 2, deep zone; and male allotype, same area but chicken liver bait #1. Our red label states “ Ptomaphagus parashant Peck & Wynne , holotype.” Paratypes, all with yellow paratype labels, seven with same locality data and five from site 2, direct intuitive searching, and two from “sweet potato bait #4” are deposited at the CMN, the Los Angeles County Museum , California Academy of Sciences , and the U.S. National Museum of Natural History (Smithsonian Institution) .

Diagnosis. The species is characterized by its smoothly surfaced and weakly faceted eye which is reduced to a horizontal diameter of less than the distance from the front margin of the eye to the posterior edge of the antennal insertion, its elongated antennae, the shape of the female spermatheca, and the different elytral tips of the two sexes.

Description. Length 3.0 mm from front of clypeus to tip of elytra. Width 1.2 mm across widest part of body, about 1/3 of the way down on the elytra. Color somewhat pale chestnut brown ( Fig. 2 ). Head finely punctured and pubescent. Eyes reduced, facet remnants only weakly distinguishable and numbering about 25, eye surface nearly smooth ( Fig. 3 A-B); eye horizontal diameter about 0.8 times (range 0.70–0.85) the distance from the anterior eye edge to the point of antennal insertion; eye surface appearing pale in color (cuticle without pigment) with reflected light. Antenna ( Figs. 3D, 4A ) elongate, extending to first quarter of elytra when laid back; segment III longer than II, segments IV-V similar, VI shorter, segments VII, IX, and X nearly equal in length and progressively slightly wider, segment VIII 3 times wider than long. Pronotum transversely striate, wider than long, widest at base, hind angles weakly acuminate. Elytra obliquely striate, about 4 times longer than broad; female apex drawn out ( Fig. 4C ), male hind margin obliquely truncate, and somewhat drawn out at tip ( Fig. 4D ). Wings reduced, variable, no venation observed; length about 3/5 length of elytra in some specimens and seemingly absent in others. Mesosternal notch weakly developed; mesosternal carina anteriorly nearly flush with mesosternum, gradually becoming higher to its rounded termination between middle legs. Legs elongate ( Fig. 4B ); male protarsi wider in basal segments than in female; all male protarsal segments longer than wide; first male protarsal segment 2.5 times larger than second and third; metafemur 4.62 times longer than wide; metatibia 12 times longer than at its widest; metatarsi all longer than wide, first segment 2.5 times longer than second and third. Aedeagus typical; parameres ending before aedeagal orifice, with 2 nearly terminal setae; stylet thin, elongate, gently sinuous; tip ( Fig. 4E ) in dorsal view gradually narrowing to apex. Spermatheca ( Fig. 4F ) with twisting central shaft, swollen apically and distally, slight raised crest at anatomically anterior end.

Variation. The only noted variation is in the size of the eye, which is more reduced in some specimens than others, and the seemingly variable state of the reduction of the flight wings (the elytra were not spread on most specimens to look for wing remnants).

Etymology. The species name, parashant , is used as a noun in apposition and was used because it is the name of the national monument where this species occurs. This monument is named for both the Grand Canyon, which is due south, and Parashant Canyon, which is one of the major canyons draining into the Colorado River of the Grand Canyon.

Study Area and Habitat. Located in northwestern Arizona, Grand Canyon-Parashant National Monument encompasses approximately 4,451 km 2 and occurs at the convergence of two geological provinces (Basin and Range and Colorado Plateau). The monument is characterized by rugged terrain containing deeply incised canyons, mesas, and mountains. Vegetation zones include plants characteristic of the Mojave Desert at lower elevations, grading through grassland and juniper shrubland to ponderosa pine forest on Mt. Trumbull (elevation 2,447 m).

The type locality for this leiodid species is PARA-1001. This cave is a small solution cave in the Kaibab limestone and has little secondary calcite deposition. Its total surveyed length and depth is 76.2 m and 10.4 m, respectively. The cave has a small south-facing vertical entrance in the bottom of a large sinkhole. The cave occurs within juniper scrublands at 1,585 m elevation. Specimens of P. parashant were collected from the lower level (or Site 2; Fig. 1 ) within the cave’ s deep (dark) zone. The deep zone environment is completely dark and characterized by relatively stable temperature, relatively constant water saturated atmosphere, and often limited to no airflow (e.g., Howarth 1980, 1982; Howarth and Stone 1990). This cave supports the largest known camel or cave cricket den (population>1,000 individuals) in Arizona (Wynne, unpublished data). This population of crickets provides a significant nutrient loading into the cave via cricket guano, cricket eggs and nymphs, as well as deceased individuals at various life stages. In other regions, the ecological importance of cave crickets is well documented (e.g., Barr 1967; Howarth 1983; Taylor 2003; Culver 2005; Poulson 2005). We suggest it is equally important for both this ecosystem as well as this new species. Cricket guano and dead crickets undoubtedly serve as substrates for the growth of bacteria and fungi (a food source for leiodid beetles).

Distribution. Ptomaphagus parashant is known from only one locality in northwestern Arizona – on the north side of the lower Colorado River and along the western extent of the Grand Canyon. JW and others have sampled 13 of the largest known caves in PARA for cavernicolous arthropods (Wynne, unpublished data); three of these caves are within a 9.7-km radius of PARA-1001. This new species was detected in only one cave, PARA-1001. Given this, we suggest that this new species represents a narrow-range endemic and may be endemic to this cave only.

Key to Species. In an earlier key to the species of Ptomaphagus ( Peck 1973) , this species fits into a modified couplet 1a: with eyes unpigmented and greatly reduced (never entirely absent), with a diameter of less than the distance between the anterior eye margin and the edge of the antennal insertion; and being cavemodified and cave-adapted (a troglobite). This would lead to couplet 2, which can be modified as follows:

2a. Troglobites in caves in Mexico..................3

2b. Troglobites in caves in the eastern United

States.........................................................4

2c. Troglobites in caves elsewhere: in NW Arizona

............ Ptomaphagus parashant , new species

Relationships. The spermatheca is the structure which has proved most useful in suggesting species relationships in the large genus Ptomaphagus , with over 60 species in the Nearctic and Neotropical regions. The shape of the spermatheca (like a reversed “S” and expanded at both ends) of P. parashant shows that the species is in the consobrinus species-group, and not the hirtus or cavernicola species-groups ( Peck 1973). Within the consobrinus species-group, the spermathecal morphology is closest to that of the troglophilic P. fisus in the southwestern U.S. (Peck and Gnaspini 1997). Both this species and troglophilic P. cocytus , a species with less reduced and clearly faceted eyes and functional wings from caves in Grand Canyon National Park (GRCA), have males with a low tooth on the metafemur, which is lacking in P. parashant . Other cave inhabiting troglophilic Ptomaphagus in the southwestern U.S. are P. californicus and Ptomaphagus inyoensis Peck and Gnaspini, 1997 , but these are less cave-modified and are known or suspected to occur in non-cave habitats as well. Also, there are two named, small-eyed, montane, leaf-litter species in New Mexico, Ptomaphagus manzano Peck, 1978 and Ptomaphagus lincolnensis Peck, 1978 , but their spermathecae (in curvature and terminal swellings) are much less similar. Additionally, there are several undescribed, smalleyed, leaf-litter inhabiting species known from small numbers in the southwestern U.S., especially the coastal mountains of California, and likely more remain undiscovered. In conclusion, the relationships of the species are obscure, but probably related to an ancestor shared with P. cocytus and P. fisus , and are clearly not related to any of the cave species in the mostly eastern hirtus and mostly Neotropical cavernicola species-groups, all in the subgenus Adelops Tellkampf.

It is worth noting that Ptomaphagus , subgenus Ptomaphagus , includes about 29 species in Eurasia, and that only one of these, Ptomaphagus (Ptomaphagus) troglodytes Blas and Vives, 1983 , is a cave-adapted species known from Grenada, Spain. Perhaps the great radiation of Leptodirini ( Leiodidae : Cholevinae ) in caves of Eurasia somehow excluded Ptomaphagus from caves there.

Figures

Fig. 2. Ptomaphagus parashant. A) Ventral view, B) Dorsal view, C) Lateral view.

Fig. 4. Ptomaphagus parashant. A) Antenna of allotype male, B) Right metathoracic leg of allotype male, view of ventral surface, C) Elytral tips of holotype female, D) Elytral tips of paratype male, E) Dorsal surface of aedeagal tip of paratype male, F) Spermatheca of holotype female. Scale bar = 0.5 mm for A, 1.0 mm for B, C, and D, 0.4 mm for E, and 0.3 mm for F.

Fig. 1. Map of PARA-1001 cave with plotted locations for bait sampling and direct intuitive searches. Ptomaphagus parashant was detected only in the lower level (or Site 2).