Research Article |
Corresponding author: Robert Hershler ( hershlerr@si.edu ) Academic editor: Frank Köhler
© 2015 Hsiu-Ping Liu, Robert Hershler, Chris Rossel.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Liu H-P, Hershler R, Rossel CS (2015) Taxonomic status of the Columbia duskysnail (Truncatelloidea, Amnicolidae, Colligyrus). ZooKeys 514: 1-13. https://doi.org/10.3897/zookeys.514.9919
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Undescribed freshwater snails (Amnicolidae: Colligyrus) from the Mount Hood region (northwestern United States) identified as a new species (commonly known as the Columbia duskysnail) in grey literature have been provided federal protection under the “survey and manage” provisions of the Northwest Forest Plan and have been placed on conservation watch lists. However, there are no published studies of the identity of these snails aside from a molecular phylogenetic analysis which delineated a close relationship between the single sampled population and C. greggi, which is distributed more than 750 km to the east of the Mount Hood area. Here we examine the taxonomic status of the Columbia duskysnail based on additional molecular sampling of mitochondrial DNA sequences (COI) and morphological evidence. We found that the Columbia duskysnail is not a monophyletic group and forms a strongly supported clade with C. greggi. The COI divergence between these broadly disjunct groups (2.1%) was somewhat larger than that within C. greggi (1.0%) but considerably less than that among the three currently recognized species of Colligyrus (8.7–12.1%). Additionally we found that the Columbia duskysnail and C. greggi cannot be consistently differentiated by previously reported diagnostic characters (size and shape of shell spire, pigmentation of body and penis) and are closely similar in other aspects of morphology. Based on these results we conclude that the Columbia duskysnail is conspecific with C. greggi.
Gastropoda , aquatic, western United States, systematics, phylogeny, conservation
The freshwater gastropod genus Colligyrus contains three currently recognized species (commonly known as duskysnails) that live in cold water seeps and springs in the northwestern United States (
Samples used for molecular analysis, with codes (used in Figs
Taxon | Code | Locality (voucher catalog number) | GenBank accession number |
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Columbia duskysnail | COL1 (N=4) |
Small spring, Brooks Meadow, middle Columbia River basin, Hood River Co., OR | KT248021 |
COL2 (N=4) |
Spring tributary, Tony Creek, middle Columbia River basin, Hood River Co., OR | KT248022 | |
COL3 (N=4) |
Bottle Prairie, middle Columbia River basin, Hood River Co., OR | KT248023 | |
COL4 (N=4) |
Spring tributary, Ramsey Creek, middle Columbia River basin, Wasco Co., OR | KT248024 | |
COL5 (N=4) |
Spring tributary, Clear Creek, Deschutes River basin, Wasco Co., OR |
KT248025 (COL5A, N=3) KT248026 (COL5C, N=1) |
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COL6 (N=4) |
Bear Creek, Hood River Co., OR |
KT248027 (COL6A, N=3) KT248028 (COL6C, N=1) |
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CL | Oak Grove Fork, Willamette River basin, Clackamas Co., OR | AY196174 | |
Colligyrus convexus | BL | Baum Lake, Pit River basin, Shasta Co., CA | AY196166 |
TS | Fall River (spring source), Pit River basin, Shasta Co., CA | AY196167 | |
MBa | Burney Creek, Pit River basin, Shasta Co., CA | AY196168 | |
MBb | Burney Creek, Pit River basin, Shasta Co., CA | AY196169 | |
Colligyrus depressus | SRa | Second spring south of Turner Ranch, Silvies River basin, Harney Co., OR | AY196170 |
SRb | Third spring south of Turner Ranch, Silvies River basin, Harney Co., OR | AY196171 | |
Colligyrus greggi | SN | Springs along Cliff Creek, upper Snake River basin, Sublette Co., WY | AY196172 |
BR | Spring at Saint Charles campground, Bear Lake basin, Bear Lake Co., ID | AY196173 | |
AM17 (N=2) |
Spring at Porcupine campground, Bear Lake basin, Bear Lake Co, ID | KT248030 | |
AM20 (N=2) |
Springs along Trail Creek, upper Snake River basin, Caribou Co., ID | KT248031 | |
Colligyrus sp. | KL | Link River, Klamath River basin, Klamath Co., OR | AY196175 |
Colligyrus? sp. | COL7 (N=1) |
Allison Springs, Puget Sound drainage, Thurston Co., WA | KT248029 |
Amnicola limosa | - | Blind Lake, Lake Michigan basin, Washtenow Co., MI | AF213348 |
The cluster of undescribed duskysnail populations in the vicinity of Mount Hood (Columbia River basin) was identified in grey literature as a new species, commonly known as the Columbia duskysnail (
The Columbia duskysnail has received considerable attention from the conservation community owing to its supposedly narrow distribution, and threats that include road construction, logging, and water diversions (
Clearly there is a need to clarify the taxonomic status of the Columbia duskysnail as a prerequisite for protection under the Endangered Species Act and other possible conservation measures. Here we address this research gap by further analysis of mtCOI sequences (for which six populations of these animals and two populations of C. greggi were newly sampled) and assessment of reported diagnostic morphologic characters.
For the molecular component of this study we newly sampled two populations of C. greggi, six populations of the Columbia duskysnail from the Lower Deschutes River and Middle Columbia-Hood River basins, and a population of another putatively undescribed species of duskysnail (from the Puget Sound region) recognized in grey literature (
MrModeltest 2.3 (
Genetic distances within and between samples were calculated using MEGA6 (
The morphologic component of the study was focused in large part on evaluating the purported diagnostic differences between the Columbia duskysnail and C. greggi. Shell parameters were compiled for two samples of the former and five samples of the latter to assess variation in spire size and shape, and other aspects of shell form. Ten to 20 adult specimens (having fully formed apertural lips) were selected from amongst the largest specimens of each sample. The height of the entire shell (SH), width of the body whorl (WBW), and height of the aperture (AH) were measured from camera lucida outline drawings using a digitizing pad linked to a personal computer (see Hershler 1989). Ratios were generated from the raw data to estimate the size of the spire relative to aperture height (SH-AH/AH) and shape of the spire (SH-AH/WBW). Sample heterogeneity of these parameters was examined through analysis of variance (ANOVA), with post-hoc testing of differences among means using the Bonferroni correction for multiple comparisons. We also performed a discriminant analysis of seven standard shell parameters (total number of whorls, height and width of entire shell, body whorl, and aperture) obtained from this same set of specimens (measurement methods as above). A classification matrix based on the resulting canonical scores was generated to assess accuracy of assignment of individual specimens to the Columbia duskysnail and C. greggi. Analyses were performed using Systat for Windows 11.00.00 (SSI 2004). Several recently collected ethanol-preserved samples of the Columbia duskysnail were examined to assess purportedly diagnostic (soft part) pigmentation patterns, and to further evaluate the distinctiveness of these animals relative to C. greggi. Variation in the number of cusps on the radular teeth (N=5) was assessed using the method of
The Columbia duskysnail COI sequences formed a strongly supported clade with C. greggi in all but the ML tree; the Bayesian topology is shown in Figure
Mean mtCOI sequence divergence (Tajima-Nei distance) among amnicolid lineages. Values are percentage ± standard deviation.
Lineage | C. greggi + Columbia duskysnail | C. convexus | C. depressus | C. sp. (KL) | C. sp. (COL7) |
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C. greggi + Columbia duskysnail | 1.2 ± 0.3 | ||||
C. convexus | 11.6 ± 1.5 | 0.0. ± 0.2 | |||
C. depressus | 10.5 ± 1.4 | 8.7 ± 1.3 | 0.0 ± 0.0 | ||
C. sp. (KL) | 10.7 ± 1.4 | 4.0 ± 0.9 | 8.5 ± 1.3 | ||
C. sp. (COL7) | 12.1 ± 1.5 | 12.8 ± 1.7 | 13.2 ± 1.6 | 11.9 ± 1.5 | |
A. limosa | 19.0 ± 1.9 | 19.2 ± 2.1 | 19.6 ± 2.1 | 19.4 ± 2.1 | 16.4 ± 1.8 |
Shell parameters (shell height, spire size and shape) and ANOVA results are reported in Table
Variation in shell parameters among samples of C. greggi and the Columbia duskysnail. Values are mean ± standard deviation, and range.
Sample | SH (mm) | Spire size (SH-AH/AH) | Spire shape (SH-AH/WBW) |
C. greggi | |||
USNM 883531 (N=12) | 2.65 ± 0.17 2.40–2.98 |
1.27 ± 0.09 1.11–1.42 |
0.88 ± 0.06 0.77–0.96 |
USNM 905375 (N=11) | 2.14 ± 0.15 1.88–2.44 |
0.87 ± 0.11 0.72–1.10 |
0.65 ± 0.06 0.58–0.76 |
USNM 905382 (N=20) | 2.64 ± 0.13 2.40–2.95 |
1.08 ± 0.07 1.00–1.23 |
0.78 ± 0.04 0.73–0.88 |
USNM 1003672 (N=11) | 2.35 ± 0.07 2.25–2.47 |
1.03 ± 0.06 0.88–1.10 |
0.72 ± 0.04 0.64–0.77 |
USNM 1075739 (N=17) | 2.82 ± 0.19 2.43–3.13 |
1.14 ± 0.10 0.99–1.34 |
0.83 ± 0.05 0.75–0.90 |
Columbia duskysnail | |||
USNM 1256484 (N=10) | 2.34 ± 0.18 2.08–2.57 |
0.98 ± 0.08 0.64–0.80 |
0.72 ± 0.05 0.64–0.80 |
USNM 1256489 (N=10) | 1.94 ± 0.26 1.67–2.47 |
0.95 ± 0.13 0.75–1.16 |
0.67 ± 0.06 0.57–0.78 |
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We were unable to confirm the purported differences in soft part pigmentation between the Columbia duskysnail and C. greggi. The pallial roof and visceral coil of the Columbia duskysnail is darkly pigmented and often black (Fig.
Radular cusp counts for C. greggi (from
C. greggi | Columbia duskysnail | |
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Central teeth, lateral cusps | 4–7 | 4–7 |
Central teeth, basal cusps | 1–2 | 1–2 |
Lateral teeth, cusps on inner side | 2–4 | 3–5 |
Lateral teeth, cusps on outer side | 3–4 | 4–5 |
Inner marginal teeth | 24–27 | 24–30 |
Outer marginal teeth | 25–33 | 23–29 |
Our molecular analysis further confirms a close relationship between the Columbia duskysnail and C. greggi and also indicates that populations of the former do not form an evolutionarily distinct, monophyletic unit. The COI sequence divergence between the Columbia duskysnail and C. greggi (2.1 ± 0.5%) is somewhat larger than differentiation within the latter (1.0 ± 0.3%) but considerably less than that among the three currently recognized congeners (8.7–12.1%). We also found that the Columbia duskysnail closely resembles C. greggi morphologically and cannot be consistently distinguished from it based on the diagnostic characters reported in grey literature (or other shell parameters). Consequently we conclude that the Columbia duskysnail is conspecific with C. greggi.
Colligyrus greggi can be added to a long list of plant and animal species that have broadly disjunct, coastal-inland distributions in the Pacific Northwest (
As mentioned in the introduction to this paper, there are numerous taxonomically unstudied populations in the northwestern United States that may be assignable to Colligyrus; it is likely that some of these are new species. Although our findings have shown that the Columbia duskysnail cannot be considered a distinct congener, the undescribed populations in the Klamath Lake basin (KL) and Puget Sound area (COL7) merit further study as candidate species given that they differ from other Colligyrus lineages by 4.0–13.2% COI sequence divergence. The positioning of the latter outside of the Colligyrus clade, together with the unusual (near planispiral) shells of these snails suggests that they may belong to a previously unrecognized component of the North American amnicolid radiation.
Colligyrus greggi.—IDAHO. Bear Lake County. USNM 905382, spring at Saint Charles campground, Bear Lake basin, 42.11°N, 111.4662°W. USNM 905375, spring at Porcupine campground, Bear Lake basin, 42.0951°N, 111.5179°W. Fremont County. USNM 1003672, Otter Springs, upper Snake River basin, 44.1545°N, 111.2132°W. OREGON. Clackamas County. USNM 1019124, Oak Grove Fork, 0.24 km upstream from Timothy Lake, Willamette River basin, 45.11076°N, 121.76156°W. Hood River County. *USNM 1256484, small spring, Brooks Meadow, middle Columbia River basin, 45.41389°N, 121.52659°W. *USNM 1256483, spring tributary, Tony Creek, middle Columbia River basin, 45.49263°N, 121.70352°W. *USNM 1256485, Bottle Prairie, west of Eightmile Creek, middle Columbia River basin, 45.39471°N, 121.49992°W. *USNM 1256488, Bear Creek, side channel, Hood River Co., OR, 45.49386°N, 121.64251°W. Wasco County. *USNM 1256486, spring tributary, Ramsey Creek, middle Columbia River basin, 45.40065°N, 121.46345°W. *USNM 1256487, spring tributary, Clear Creek, Deschutes River basin, 45.14148°N, 121.58495°W. WYOMING. Sublette County. USNM 883531, Cliff Creek, tributary springs, upper Snake River basin, 43.2454°N, 110.5002°W.
Colligyrus sp.—WASHINGTON. Thurston County. *USNM 1258917, Allison Springs, Puget Sound drainage, 47.04432°N, 122.98454°W.
This project was supported by an award from the Bureau of Land Management, Oregon State Office (L11AC20325, modification no. 1). We thank Kelli van Norman for facilitating this funding and for her constant encouragement and support throughout the project. We also thank Freya Goetz for inking the anatomical drawings; and Yolanda Villacampa for measuring shells, counting radula cusps, and preparing scanning electron micrographs.