A review of the Nearctic genus Prostoia (Ricker) (Plecoptera, Nemouridae), with the description of a new species and a surprising range extension for P. hallasi Kondratieff & Kirchner

Abstract The Nearctic genus Prostoia (Plecoptera: Nemouridae) is reviewed. Prostoia ozarkensis sp. n. is described from the male and female adult stages mainly from the Interior Highland region encompassing portions of Arkansas, Missouri, and Oklahoma. Prostoia ozarkensis sp. n. appears most closely related to two species, one distributed broadly across the western Nearctic region, P. besametsa (Ricker), and one found widely throughout the central and eastern Nearctic regions, P. completa (Walker). A surprising range extension is noted for P. hallasi Kondratieff & Kirchner, a species once known only from the Great Dismal Swamp, from small upland streams in southern Illinois. Additional new state records are documented for P. besametsa, P. completa, P. hallasi and P. similis (Hagen). Taxonomic keys to Prostoia males and females are provided, and scanning electron micrographs of adult genitalia of all species are given.

Prostoia besametsa is the sole species found in the western Nearctic region, distributed broadly from California east to New Mexico and north to Alaska (Baumann et al. 1977, Stewart and Oswood 2006, DeWalt et al. 2013. Prostoia completa and P. similis are both found widely throughout the central and eastern Nearctic regions (DeWalt et al. 2013). Prostoia hallasi, in contrast, has been reported only from the Great Dismal Swamp Kirchner 1984, Kondratieff et al. 1995), an Atlantic Coastal wetland located in North Carolina and Virginia (Traylor 2010).
Prostoia males are easily identified among Nemouridae by their simple, elongate, anteriorly-recurved epiproct that is comprised almost entirely by the ventral sclerite (Baumann 1975). The dorsal sclerite is reduced to a pair of lateral arms located along each side of the epiproct base, except in P. hallasi where they are secondarily absent (Ricker 1952, Kondratieff andKirchner 1984). Wing coloration ranges from uniformly dark brown in P. hallasi to mottled with a distinctive light band near the apex in all other species.
For several years, Bill P. Stark (Mississippi College, Clinton, Mississippi) and the second author suspected that P. completa from the Ozark Plateau region of northern Arkansas, southern Missouri, and eastern Oklahoma represented an undescribed species. The new species is described herein, with brief anecdotes and new state records of the four previously-described species. Species keys to the male and female adult stages are provided.

Materials and methods
Prostoia specimens used in this study were obtained from, or deposited in, the follow- All specimen records for P. hallasi and the new species were included herein. Due to the large volume of material examined for P. besametsa, P. completa, and P. similis, however, these data are available only in a corresponding appendix (see Suppl. material 1 at end of paper).
Locality data, in decimal degrees, for each specimen record were obtained either directly with hand-held GPS units on site or georeferenced from museum label data (if possible). Specimens were studied with scanning electron microscopy (SEM) with a Philips XL30 ESEM FEG electron microscope at Brigham Young University. In dorsal view, anterior portion of ventral sclerite parallel-sided beyond recurved base (Figs 9-10); in lateral view, posterior portion of ventral sclerite only slightly deflected ventrally (Fig. 11); tip of ventral sclerite slightly deflected upward, parallel-sided and subquadrate apically (Figs 9,12,14); lateral arms sickle-shaped, gradually recurved (Fig. 15)  The 7 th and 8 th abdominal sterna not fused medially, with a well-developed subgenital plate that is convex, extending over the anteromedial margin of the 9 th sternum and very slightly notched medially (Fig. 24)   Remarks. Prostoia besametsa, P. completa and P. ozarkensis sp. n. appear to form a species group based on structural similarities of the male ventral sclerite and lateral arms of the dorsal sclerite, and the female subgenital plate. The Black Hills region of eastern Wyoming and western South Dakota, plus the Sand Hills region of northwestern Nebraska, mark the eastern edge of this widespread western Nearctic species in the USA (Fig. 41), and well distant from the closest distribution point of P. completa (Fig. 41) and P. ozarkensis sp. n. (Fig. 42) (Huntsman et al. 1999, DeWalt et al. 2013. Prostoia besametsa is typically found in greatest numbers in large streams and small rivers.

Prostoia completa (Walker)
http://species-id.net/wiki/Prostoia_completa http://lsid.speciesfile.org/urn:lsid:Plecoptera.speciesfile.org: TaxonName:6101  Figs 9-16, 41 Nemoura completa Walker, 1852:191. Holotype ♂ (British Museum of Natural History, London), Nova Scotia, Canada Nemoura glabra (in part) Claassen, 1923:281. Syn. Illies, 1966 Nemoura glabra: (in part) Needham & Claassen, 1925:202. Nemoura completa: Ricker 1938 Nemoura (   Remarks. This species is distributed from Atlantic Canada to South Carolina and westward to Minnesota and Iowa (Fig. 41). Characteristics of the male epiproct remain constant from eastern Canada to the southeastern United States, without any indication of a north-south cline. However, populations from the northern Midwest are somewhat variable. The prior records of P. completa from the Interior Highland region, namely the Ozark Plateau region (e.g. Poulton and Stewart 1991), now likely refer only to P. ozarkensis sp. n., but very few specimens were available for this study. Specimens collected sporadically from the only locality in southern Illinois (Webb 2002, DeWalt andGrubbs 2011) were reexamined and now are considered P. ozarkensis sp. n. This species was recently listed in Illinois as endangered due to it occurring in a single location in the state (Illinois Endangered Species Protection Board 2011). Prostoia ozarkensis sp. n. is very closely related to P. completa and separable only by experts as this time. Examination of the relatedness of these two species and congeners using genetic markers is warranted given the implications for conservation status within Illinois.
Although the ranges of P. completa and P. similis (Fig. 42) overlap extensively throughout the eastern Nearctic region, the former species is typically associated with large streams and small rivers. Prostoia completa is less commonly collected from upland, headwater streams, except in the northeastern Nearctic region where both species sometimes occur at the same locality. Remarks. This species was once considered unique amongst Nearctic Nemouridae in that it was known only from low gradient coastal streams in the Great Dismal Swamp Kirchner 1984, Kondratieff et al. 1995). The discovery of localities north in New England and south to Georgia was not too surprising since these are range extensions along the Atlantic Coastal Plain (Fig. 42). This species should eventually be found in coastal regions within the intervening states (i.e. Delaware, Maryland, New Jersey, New York, Pennsylvania, and South Carolina).

Prostoia hallasi
We initially anticipated that the populations from the Shawnee Hills region of southern Illinois represented an undescribed species. Both Illinois sites were small, upland tributaries ca. 1 m wide and very distinct from the description of the type locality (Kondratieff and Kirchner 1984). Yet the SEM images of the epiproct from specimens from several locations, particularly of the complex ornamentation of the terminus of the ventral sclerite, showed unexpected across-site similarity and no evidence that the southern Illinois populations represented an undescribed species. The epiproct terminus of the populations from Essex Co., Virginia (Fig. 17), coastal Connecticut (Fig. 20), southern Illinois (Fig. 21) and the type locality in eastern Virginia (Kondratieff and Kirchner 1984, their Fig. 6) appear indistinguishable as such: the distal anterior tip is slightly bifurcate, a small ventral subterminal knob is present, and the subterminal forked structure includes paired, ventrally-directed triangular processes and paired somewhat dorsally-directed subtruncate processes. Females from southern Illinois were indistinguishable from those from the Connecticut and Essex Co., Virginia (Fig. 24) localities noted above.

Prostoia ozarkensis Baumann & Grubbs, sp. n.
http://zoobank.org/8DE0A193-C546-46EB-A70E-DF8FEAFEBA33 http://species-id.net/wiki/Prostoia_ozarkensis http://lsid.speciesfile.org/urn:lsid:Plecoptera.speciesfile.org: TaxonName:463936  Figs 25-32, 42 Description. Male. Macropterous. Forewing length 7.0-8.0 mm; body length 6.0-6.5 mm. Wings mottled with light band in forewing beyond cord. General body color brown. Epiproct ventral sclerite recurved over abdomen, gradually widening anterior to base, widest in distal third, narrowing mark to an acute, parallel-sided tip, rounded apically ; recurved portion of ventral sclerite deflected downward at approximately the midpoint (Fig. 28) shaped epiproct tip and the western Nearctic distribution of P. besametsa easily separates this species from P. completa and P. ozarkensis sp. n. The epiproct of P. completa and P. ozarkensis sp. n. narrow markedly to an acute, parallel-sided tip. In addition, the lateral arms of P. besametsa do not extend past the epiproct base whereas in P. completa and P. ozarkensis sp. n. the lateral arms are noticeably longer. Prostoia ozarkensis sp. n. closely resembles P. completa in both the male and female adult stages. Whereas females of the two species appear indistinguishable, males can be separated by close examination of details of the lateral arms and the overall shape of the ventral sclerite. The lateral arms of P. ozarkensis sp. n. are short, pointed apically, and bear a stout nub on the outer surface (Fig. 29). While in P. completa the lateral arm is longer, scythe-shaped, and has a smooth outer margin (Fig. 15). The ventral sclerite of P. ozarkensis sp. n. is recurved in lateral aspect, especially along the ventral margin (Fig. 28) and expanded dorsally toward the apex (Fig. 25). Conversely, in P. completa the ventral sclerite is nearly straight in lateral aspect (Fig. 11) and narrow and nearly parallel-sided dorsally (Figs 9, 10).
Prostoia ozarkensis sp. n. overlaps in range only with P. similis (Fig. 42), but the combination of the long, sinuate lateral arms and the well-developed lateral lobes of the female 8 th sternum easily distinguish the latter species from each of the four other Prostoia species. With the surprising discovery of P. hallasi from southern Illinois, the distribution of this species is likely far from understood and there is no reason to preclude its presence west of the Mississippi River into the Interior Highland region. The ornate epiproct tip and absence of lateral arms of P. hallasi are distinctive features that make it easy to identify males of this species. Additionally, P. hallasi is the only Prostoia species with a convex subgenital plate.
Remarks. Prostoia ozarkensis sp. n. specimens from the Ozark Plateau, including the Boston Mountains, consistently exhibit distinctive male characters that set it apart from widespread P. completa. Specimens from states to the east, namely Indiana and Kentucky, are more difficult to separate consistently and even show variability in the same population. The P. completa records presented in Poulton and Stewart (1991) likely now pertain to P. ozarkensis sp. n., but very few of their specimens were available for study. The same also applies for P. completa reported in Stark and Stewart (1973), Ernst et al. (1984), Ernst and Stewart (1985a, 1985b, 1986, Jop and Stewart (1987), Phillips and Kilambi (1994), and Harp and Robison (2006).