Hydroscapha redfordi Maier, Ivie, Johnson, and Maddison

Maier, Crystal A., Ivie, Michael A., Johnson, James B. & Maddison, David R., 2010, A New Northern-Most Record for the Family Hydroscaphidae (Coleoptera: Myxophaga), with Description of a New Nearctic Species, The Coleopterists Bulletin 64 (4), pp. 289-302 : 292-296

Hydroscapha redfordi Maier, Ivie, Johnson, and Maddison , new species

Diagnosis. The limited distribution of H. redfordi immediately sets it apart from its congeners. Hydroscapha redfordi is distinguished from all other examined populations of Hydroscapha by its small eyes, dark brown color, and the combination of wide tentorial bridge ( Fig. 16 ) [cf. with the narrow bridge in H. natans ( Fig. 17 )] and narrow disc of the mesoventrite ( Fig. 3 ) [cf. with the wide mesoventrite in H. natans ( Fig. 4 )]. The wide tentorium, with the right vs. left arms separated by a distinct, straight bridge distinguishes it from H. natans and the Sunbeam population, which have the tentorial arms nearly adjacent, and the short tentorial bridge appearing curved ( Fig. 17 ). The disc of the mesoventrite ( Fig. 3 ) is narrower relative to its length than that of H. natans ( Fig. 4 ), and has projecting antero-lateral angles that distinguish it from the Kirkham Hot Springs and the Hot Creek Falls populations. The metaventrite is 3.7 times wider than long at its widest point, and is narrower between the mesocoxae ( Fig. 5 ) than in H. natans ( Fig. 6 ). In addition, all specimens of H. redfordi examined were brachypterous (almost micropterous), with the setae at the margin of the hind wings barely extending to the posterior margin of the elytra when folded. Also, the tarsal claws of H. redfordi have a broader base ( Fig. 9 ), as opposed to a narrower base in H. natans ( Fig. 10 ). Abdominal segment VIII (the last visible segment) of the males also differs between species, with H. redfordi ( Fig. 7 , 11 ) having the tergite widest subbasally as opposed to widest basally in H. natans ( Fig. 8 ). In the female genitalia of H. redfordi , the dorsal paired structure possesses a submedial claw-like tooth ( Fig. 15 ) as opposed to two apical teeth in H. natans (Reichardt and Hinton 1976, Fig. 45).

The 28S rDNA sequences of H. natans and H. redfordi are identical for the examined 975 base pair piece, except for one position at which H. natans has an adenine and H. redfordi has a guanine. The two species are much more different in COI sequence: in the examined 658 base pair region, the three H. natans and three H. redfordi have 36 positions at which bases consistently differ ( Fig. 20).

Description. Length 1.6–1.8 mm, width 0.3– 0.6 mm at widest point. Body fusiform, convex, medium brown; dorsal and ventral surfaces sparsely setose ( Figs. 2 , 18 , 19G–H ). Head: Prognathous, almost as wide as anterior margin of pronotum, slightly deflexed, fitted into prothorax; eye reduced, almost completely contained in outline of head, with small bulge near posterior margin ( Fig. 16 ); antenna 8-segmented, inserted immediately in front of eyes, terminal segment longer than previous three combined, paddle-shaped, flattened, with sensilla at apex; pedicel shorter than scape, longer than any of antennomeres III–VII; mandibles bidentate at apex; labrum with even row of setae at border; tentorial arms separated by straight tentorial bridge ( Fig. 16 ). Thorax: Pronotum transversely convex; posterior angles acute; surface with sparse, even punctation and setae; scutellum much wider than long, partially obscured by pronotum; prosternum short, extending laterally nearly to hypomeron; procoxal cavities open posteriorly; mesoventrite fused with metaventrite, disc of mesoventrite tricornate anteriorly ( Fig. 3 ), antero-lateral angles produced anteriorly, distance between lateral points approximately 1.1× length of disc; mesocoxae moderately separated by junction of mesosternum and metasternum; metaventrite long ( Fig. 5 ), 3.7× wider than long at widest point, sparsely setose, lobed between meso- and metacoxae; metepisternum narrowed posteriorly; elytra truncate, quadrate, 1.5× long as wide, sparsely setose; hind wings greatly reduced, barely reaching posterior margin of elytra, fringed with long setae; legs with sparse rows of short, spine-like setae, tarsal formula 3-3-3, apical tarsomere longer than other two combined, claws prominent, with wide basal lobe ( Fig. 9 ); metacoxa with posterior face, coxal plate prominent ( Fig. 18 ). Abdomen: Tapering posteriorly; tergites III and IV with mat of dense setae, less dense on tergite IV; patch of recumbent setae postero-medially on abdominal ventrite V in males; aedeagus simple, lacking parameres ( Fig. 12 ); penultimate ventrite of males with deep notch, notch absent in females; male tergite VIII widest subbasally ( Fig. 7 ); in females, dorsal paired structure truncate with submedial claw-like tooth ( Fig. 15 ).

DNA Sequences. COI sequence as in Fig. 20.

Distribution. Known from two hot springs in northeastern Idaho: Jerry Johnson Hot Springs and Weir Hot Springs, both of which flow into the Lochsa River.

Type Material. Holotype: “ IDAHO: Idaho Co.; Jerry Johnson Hot Springs; 10 mi W. Powell Junction; 46°27′45.7″N; 114°52′3″W; 28 October 2007; M.A. Ivie, J.B. Johnson, and C.A. Maier col’ rs / Hydroscaphidae ;:? Hydroscapha .” From MTEC, deposited in California Academy of Sciences . Paratypes: 394 exs. – same data as holotype (230 MTEC, 12 JBJC, 25 WFBM, 50 Oregon State Arthropod Collection , 10 British Museum of Natural History , 10 Naturhistorisches Museum Wien , 10 National Museum of Natural History , 10 University of Arizona Insect Collection , 10 Australia National Insect Col- lection, 10 University of Kansas Natural History Museum). 48 – IDAHO : Idaho Co.; Jerry Johnson Hot Springs; 10 mi W. Powell Junction; 46°27′ 45.7″N; 114°52′3″W; 5 SEPT 08 ; J.B. Johnson; M. Tosch; M. Hill; F.W. Merickel (4 JBJC, 44 WFBM) .

Non-Type Material. IDAHO: Idaho Co.; Weir Creek Hot Springs,; 20 mi W. Powell Junction; 46°27.947′–115°1.982′; 5 SEPT 2008 M. Tosch; M. Hill; J.B. Johnson; (9 WFBM, 2 JBJC) .

Etymology. This species is named in honor of actor/conservationist Robert Redford, whose 1972 portrayal of the semi-fictional Jeremiah Johnson in the film of the same name brought attention to the character as well as the beauty of the region. One of us (MAI) was so affected by the film that he chose to spend his life and career in the Rockies. The type locality of this species, Jerry Johnson Hot Springs, is named for Redford’ s character, but it is Redford’ s continuing work to safeguard the wild legacy of the Rocky Mountains that makes this name a fitting tribute.

Natural History. Hydroscapha redfordi is limited to hot springs, where it lives in a hygropetric environment on nearly vertical rock faces covered in mats of filamentous algae ( Fig. 1 ). The population was densest in about 1 cm deep flows approximately 3 m from where the hot springs emerged from the ground, about 15 m from the confluence with Warm Creek, a tributary of the Lochsa River. This is the area of densest algal growth. Numbers decreased below this point, as did algal density. It is important to note that no beetles were collected below “bathing pools” and we suspect that various soaps and oils present where people bathe render the habitat unsuitable for habitation by hydroscaphids. Water temperature in the inhabited zone was approximately 50°C. This spring is unique in the region because it shows little evidence of mineral deposits. Lolo Hot Springs, located 30 km east of Jerry Johnson Hot Springs in Lolo, Montana, has significantly more mineral deposits, less algae, and yielded no Hydroscapha .

Remarks. Many of the morphological characters which distinguish H. redfordi from H. natans are apparently the result of changes associated with brachyptery. Reichardt and Hinton (1976) concluded that brachypterous Hydroscapha found in a hot spring in southern Idaho (Hot Creek Falls) were simply H. natans adapted for hot springs. However, examination of specimens from that spring (see below) revealed significant morphological differences between them and both H. redfordi and alate H. natans , and we suspect that the Hot Creek Falls population belongs in neither of the described species, but in a third, undescribed species. In addition, we examined the specimens from two other hot springs on the Snake River Plains of southern Idaho, which display significant morphological differences from any of these three, and probably also represent a new species (see below). However, we will not describe them here for lack of genetic information.

As noted in the diagnosis, H. redfordi differs from H. natans by one base in the sequenced portion of 28S, but 36 bases in the sequenced region of COI. Three of these fixed differences in COI represent non-synonymous changes, resulting in three amino acid differences between the two species; at all three sites, H. redfordi has a serine, whereas H. natans has glycine, asparagine, or alanine. The percent differences between individual H. redfordi range from 0.16% to 0.47%, between individual H. natans from 0.46% to 2.18%, and between individual H. redfordi and H. natans from 6.7% to 7.9%. The unrooted maximum likelihood tree for the COI sequences ( Fig. 21 ) shows the divergence between the two populations, as well as some notable variation within H. natans .

Figures

Figs. 16–17. Tentoria. 16) Hydroscapha redfordi; 17) Hydroscapha natans.

Figs. 3–8. Hydroscapha spp. Disc of mesoventrites. 3) H. redfordi, disc of mesoventrite; 4) H. natans, disc of mesoventrite; 5) H. redfordi, metaventrite; 6) H. natans, metaventrite; 7) H. redfordi, male abdominal tergite VIII; 8) H. natans, male abdominal tergite VIII.

Figs. 9–10. Protarsal claws. 9) Hydroscapha redfordi; 10) Hydroscapha natans. Arrows indicate base of claw.

Figs. 11–15. Hydroscapha redfordi. 11) Male abdominal segment VIII, ventral view; 12) Aedeagus; 13) Female tergite VIII; 14) Female sternite VIII; 15) Female genitalia, d – left dorsal paired structure, v – left ventral paired structure, m – median lobe, arrow indicates claw-like tooth (terminology following Reichardt and Hinton [1976], compare with their Fig. 45).

Figs. 1–2. 1) Habitat of Hydroscapha redfordi, Jerry Johnson Hot Springs, Idaho Co., ID; 2) Hydroscapha redfordi.

Fig. 18. Hydroscapha redfordi, ventral habitus.

Fig. 19. Diversity in Hydroscapha populations in the United States: A) H. natans, Arizona, Santa Cruz Co., B) H. natans, California, Arroyo Mocho, C) H. natans, California, Alameda Co., D) Hydroscapha sp., Nevada, Amargosa Hot Springs, E) Hydroscapha sp., Idaho, Hot Creek Falls, F) Hydroscapha sp., Idaho, Sunbeam Hot Springs, G) H. redfordi, Idaho, Jerry Johnson Hot Springs, H) H. redfordi, Idaho, Weir Hot Springs.

Fig. 21. Unrooted maximum likelihood tree for the COI data.