The endemic gastropod fauna of Lake Titicaca : correlation between molecular evolution and hydrographic history

Lake Titicaca, situated in the Altiplano high plateau, is the only ancient lake in South America. This 2- to 3-My-old (where My is million years) water body has had a complex history that included at least five major hydrological phases during the Pleistocene. It is generally assumed that these physical events helped shape the evolutionary history of the lake´s biota. Herein, we study an endemic species assemblage in Lake Titicaca, composed of members of the microgastropod genus Heleobia, to determine whether the lake has functioned as a reservoir of relic species or the site of local diversification, to evaluate congruence of the regional paleohydrology and the evolutionary history of this assemblage, and to assess whether the geographic distributions of endemic lineages are hierarchical. Our phylogenetic analyses indicate that the Titicaca/Altiplano Heleobia fauna (together with few extralimital taxa) forms a species flock. A molecular clock analysis suggests that the most recent common ancestor (MRCAs) of the Altiplano taxa evolved 0.53 (0.28–0.80) My ago and the MRCAs of the Altiplano taxa and their extralimital sister group 0.92 (0.46–1.52) My ago. The endemic species of Lake Titicaca are younger than the lake itself, implying primarily intralacustrine speciation. Moreover, the timing of evolutionary branching events and the ages of two precursors of Lake Titicaca, lakes Cabana and Ballivián, is congruent. Although Lake Titicaca appears to have been the principal site of speciation for the regional Heleobia fauna, the contemporary spatial patterns of endemism have been masked by immigration and/or emigration events of local riverine taxa, which we attribute to the unstable hydrographic history of the Altiplano. Thus, a hierarchical distribution of endemism is not evident, but instead there is a single genetic break between two regional clades. We also discuss our findings in relation to studies of other regional biota and suggest that salinity tolerance was the most likely limiting factor in the evolution of Altiplano species flocks

A systematic review of the hydrobiid snails (Gastropoda: Rissooidea) of the Great Basin, Western United States : 1. Genus Pyrgulopsis

A recently completed field survey of springs throughout the Great Basin yielded collections of hydrobiid snails from more than 500 sites, and revealed a wealth of undescribed diversity of these small gastropods. In this, the first or a two-part taxonomic series treating this material, 58 new species of Pyrgulopsis Call & Pilsbry, 1886, are described; and new records are provided for 10 previously described members of this genus. Assignment of these novelties to Pyrgulopsis is done with the acknowledgement that this large genus, as currently constituted, is probably not monophyletic, but a more refined classiffcation of these snails reflecting evolutionary relationships must await preparation of a phylogenetic analysis, which is beyond the scope of this work. Pyrgulopsis occur in a variety of spring-fed water bodies in the Great Basin, including brackish and/or thermal habitats. Although a few species are widespread in the region, local endemism is prevalent lind 22 of the new species are known only from single localities. Several areas contain concentrations of locally endemic snails which may represent species flocks, notably Duckwater Valley (seven species) and southern Steptoe Valley (five species). This fauna is hugely distributed in an allopatric fashion, although a few springs harbor two or three species. Most of the springs inhabited by hydlrobiids in the region are small, fishless, and have been ignored by state and federal land management agencies. However, many of these sites are degraded by livestock grazing, water withdrawal, anti other activities and will require protection in order to conserve snails and other native aquatic biota. Two of the novellies described herein have become extinct during the past two decades

A systematic review of the hydrobiid snails (Gastropoda: Rissooidea) of the Great Basin, Western United States : 2. Genera Colligyrus, Eremopyrgus, Fluminicola, Pristinicola, and Tryonia

This second and final part of a taxonomic treatment of hydrobiid snails of the Great Basin region in the western United States (based principally on material collected during a recently completed field survey) focuses on fauna other than the genus Pyrgulopsis. A new genus of small amnieoline snails, Colligyrlls, is proposed for Hydroia greggi Pilsbry, 1935, together with a new species from the Harney Lake basin of Oregon. This group is strongly differentiated from other amnicolines by a unique female genitalic groundplan. New records are provided for three species of Fluminicola, and two new congeners are described from the northwest Great Basin, both of which had previously been confused with F. turbiniformis (Tryon, 1865). A new genus of cochliopine snails, Eremopyrgus, is erected for a new species from Steptoe Valley, Nevada. Eremopyrgus is distinguished from other cochliopines by unique aspects of its glandular penial lobes and other genitalic features. New records are provided for two species of Tyronia, and a new congener is described from thermal springs in central Nevada. Several new records of Pristincola hemphilli (Pilsbry, 1890) from the extreme northwest Great Basin are provide

A systematic review of the hydrobiid snails (Gastropoda: Rissooidea) of the Great Basin, Western United States. Part 2. Genera Colligyrus, Eremopyrgus, Fluminicola, Pristinicola, and Tyronia

Volume: 42Start Page: 306End Page: 33

Pyrgulopsis milleri Hershler & Liu, 2010, sp. nov.

Pyrgulopsis milleri sp. nov. (Figs 6–8) Types. Holotype (Fig. 6 A), SBMNH 83651, creek 0.7 mile (1.13 km) east of Pierpoint Spring on (California) Hwy 190, approximately 15.6 miles (25.1 km) east of Springville, Tule River drainage, Tulare County, California, Walter B. Miller, 1 /viii/ 1964. Paratypes, SBMNH 74688, USNM 1132568 (from same lot, 211 + 6 dry shells, respectively). Etymology. In honor of deceased zoologist Walter B. Miller, an intrepid collector of western North American nonmarine mollusks (Hochberg & Roth 2001) who first discovered this novelty in 1964. Referred material. CALIFORNIA. Tulare County: SBMNH 74687, Pierpoint Spring, 6.5 miles (10.46 km) east of Tule River power house, 353028 E, 4000829 N (approximate coordinates), Walter B. Miller, 31 / vii/ 1964. USNM 905257, ibid., Robert Hershler, 26 /vi/ 2000. SBMNH 74540, spring along Hwy 190 7 miles (11.23 km) east of Tule hydroelectric plant, Walter B. Miller, 25 /i/ 1963. Diagnosis. A medium-sized species having ovate- to narrow-conic shell with weakly convex whorls. Penis usually alobate; filament medium length; penial ornament usually consisting of a small ventral gland. Description. Shell (Fig. 6 A–D) ovate- or narrow-conic, height about 2.5 –4.0 mm; whorls 4.25–5.25. Periostracum tan, thin, often covered with dark deposits. Protoconch (Fig. 6 E) near planispiral, 1.3–1.5 whorls, diameter about 380 µm, surface weakly wrinkled near apex (Fig. 6 F), otherwise smooth. Teleoconch whorls weakly convex, sometimes narrowly shouldered, last 0.25 whorl rarely slightly loosened; sculpture of collabral growth lines. Aperture ovate, angled adapically. Inner lip complete, usually adnate, slightly thickened internally; columellar shelf absent; outer lip thin, weakly prosocline. Umbilicus narrow. Operculum (Fig. 6 G) thin, flat, light amber, multispiral with eccentric nucleus; last quarter whorl frilled on outer side; inner side (Fig. 6 H–I) having attachment scar border slightly thickened almost all around. Radula taenioglossate (Fig. 7 A), having about 55 well-formed rows of teeth. Central teeth (Fig. 7 B) about 28 µm wide, cutting edge concave; lateral cusps 3–6; central cusp large, U-shaped; basal cusp 1, small; basal tongue V-shaped, about as long as lateral margins. Lateral tooth (Fig. 7 C) face rectangular, angled; central cusp large, U-shaped; lateral cusps 2–4 (inner), 3–5 (outer); outer wing medium width, straight, about 200 % length of cutting edge; basal tongue well developed. Inner marginal teeth (Fig. 7 D) having 17–21 cusps. Outer marginal teeth (Fig. 7 E–F) having 19–28 cusps; inner edge having long, rectangular wing. Radula data were from USNM 905257. Head-foot generally pale. Snout usually pale, but sometimes light to dark brown. Pallial roof, visceral coil dark brown or black. Ctenidium well developed, positioned a little in front of pericardium; ctenidial filaments about 20, broadly triangular. Osphradium narrow, positioned slightly posterior to middle of ctenidium. Prostate gland large, bean-shaped, with about 40 % of length in pallial roof. Anterior vas deferens opening from ventral edge of prostate gland a little in front of posterior pallial wall, section of duct on columellar muscle straight. Penis (Fig. 8 A–C) medium-sized, base rectangular, inner edge smooth; filament short or medium length, tapering, slightly oblique; lobe usually absent, nub-like when present (Fig. 8 C). Terminal gland (observed in one specimen) small, ovate, positioned on ventral surface of lobe. Ventral gland small, ovate, centrally positioned, borne on raised swelling. Penial duct narrow, nearly straight. Penis entirely pale or with filament variably pigmented by black granules. Female glandular oviduct and associated structures shown in Figure 8 D–F. Coiled oviduct a small, proximally kinked, posterior-oblique loop. Bursa copulatrix small, narrowly ovate, horizontal, about 50 % overlapped by albumen gland. Bursal duct about as long as bursa, medium width, opening from distal edge, partly embedded in albumen gland. Seminal receptacle small, pouch-shaped, positioned along ventral edge of proximal bursal duct; duct short. Albumen gland a little shorter than capsule gland, having very short pallial section. Capsule gland composed of a single tissue section. Genital aperture a terminal slit. Shell measurements (mean + standard deviation in parentheses): height 3.00–4.00 mm (3.42 + 0.35), width 2.00– 2.50 mm (2.17 + 0.12), body whorl height 2.25–2.75 mm (2.45 + 0.15), body whorl width 1.70–2.19 mm (1.87 + 0.13), aperture height 1.36–1.61 mm (1.46 + 0.07), aperture width 1.15–1.41 mm (1.25 + 0.06), shell width/height 0.58–0.69 (0.64 + 0.03), body whorl height/shell height 0.67–0.76 (0.72 + 0.02), aperture height/ shell height 0.39–0.47 (0.43 + 0.02) (paratypes, SBMNH 74688, n = 30). Height 2.91–3.46 mm (3.12 + 0.14), width 1.77–2.16 mm (1.97 + 0.08), body whorl height 2.10–2.57 mm (2.30 + 0.10), body whorl width 1.52–1.80 mm (1.65 + 0.07), aperture height 1.23–1.57 mm (1.39 + 0.07), aperture width 1.08–1.31 mm (1.16 + 0.06), shell width/height 0.57–0.66 (0.63 + 0.02), body whorl height/shell height 0.68–0.77 (0.74 + 0.02), aperture height/ shell height 0.39–0.48 (0.45 + 0.02) (SBMNH 74687, n = 30). Measurements of holotype: height, 3.70 mm, width 2.36 mm, body whorl height 2.67 mm, body whorl width 2.01 mm, aperture height 1.59 mm, aperture width 1.39 mm, shell width/height 0.64, body whorl height/shell height 0.72, aperture height/shell height 0.43, 5.0 whorls. Distribution, habitat and conservation status. Pyrgulopsis milleri is known only from its type locality area, which consists of spring-fed waters along a very short (ca. 1.0 km) reach of the South Fork of the Middle Fork Tule River drainage. Pierpoint Spring spills down a rock face into a ditch right alongside Hwy 190; part of its flow issues from a pipe (see Jenkins & Jenkins 1995: 153 for a photograph of this spring). The first author collected P. milleri from aquatic vegetation in this ditch; density was low. There is no information on the habitat and current status of the other two populations which Miller sampled during the early 1960 ’s. (The first author did not attempt to access these sites during his brief visit to the area in 2000.) Pyrgulopsis milleri is distributed within a parcel of patented (private) land that is nested within the Giant Sequoia National Monument (Sequoia National Forest). This species currently has no protection and may be threatened by the diversion of Pierpoint Spring, physical disturbance (e.g., trampling, pollution) associated with the frequent use of this spring as a drinking water supply by travelers on CA Highway 190 (Jenkins & Jenkins 1995: 153), and the planned local widening of this road (CDOT 2009). Remarks. Pyrgulopsis milleri differs from closely similar P. stearnsiana, which ranges into the lower portion of the Tule River basin (Hershler unpublished), in its broader central cusps on the central radular teeth, shorter pallial section of the albumen gland, greater overlap of the bursa copulatrix by the albumen gland, absence of a bend or loop in the anterior vas deferens, presence of a ventral gland on the penis and absence (except in one specimen) of a terminal gland. Pyrgulospis milleri was most similar to P. stearnsiana from the Santa Clara River basin (21 AA) in its mtCOI sequences (2.8 % divergence) and differed from other specimens of this species by 3.3–8.4 %. Thus, as with P. castaicensis (described above), both morphological and genetic evidence indicate that this snail is a new species. Based on the road distances provided by Miller we infer that Pierpoint Spring is the well known (unnamed) spring that is shown on USGS maps along the north side of Hwy 190 about 0.6 km east of the Pierpoint Springs Resort and 1.6 km east of Camp Nelson.Published as part of Hershler, Robert & Liu, Hsiu-Ping, 2010, Two new, possibly threatened species of Pyrgulopsis (Gastropoda: Hydrobiidae) from southwestern California, pp. 1-17 in Zootaxa 2343 on pages 10-15, DOI: 10.5281/zenodo.19333

A new species of hydrobiid snail of the genus Pyrgulopsis from northwestern Nevada

Volume: 43Start Page: 367End Page: 37