Physa natricina Taylor 1988, junior synonym of Physa acuta ...

chowan.edu

Physa natricina Taylor 1988, junior synonym of Physa acuta ...

Physa natricina Taylor 1988, junior synonym of Physa acuta Draparnaud,

1805 (Pulmonata: Physidae)

D. CHRISTOPHER ROGERS 1,3 and AMY R. WETHINGTON 2

1

EcoAnalysts, Inc., 166 Buckeye Street, Woodland, California 95695, USA. Email:

crogers@ecoanalysts.com.

2

Department of Biology, Chowan University, Murfreesboro, North Carolina 27855, USA. Email:

wethia@chowan.edu.

3 Corresponding author.

Running Head: Physa synonymy

Abstract

Physa natricina Taylor, 1988 is reported as a narrow range endemic species from the Snake River in

Idaho, USA and is currently protected under the federal Endangered Species Act. We examined all

available type material as well as more than 1,500 specimens of Physa collected from the Snake River and

adjacent areas over the past twelve years and compared them to the original descriptions and the type

material. No material collected from the Snake River, nor from the paratype series, could be confidently

ascribed to P. natricina using both the internal and external morphological characters defined in the

original description, nor by direct comparison to the holotype. Furthermore, the holotype and paratypes all

have internal and external morphology that is accommodated within the natural range of variation of the

polymorphic Physa acuta Draparnaud, 1805. Therefore P. natricina is conspecific with P. acuta, a

common, widespread species.

Key words: Morphological species concept, Snake River, Idaho, endangered species, conservation,

mollusks, Gastropoda, freshwater snails.

Introduction

Physidae is one of the most common and widely distributed families of pulmonate gastropods in the world

(Burch 1989; Dillon 2000; Dillon et al. 2002; Taylor 2003). Recent studies involving sequence data,

isozyme data, behavior and no choice breeding experiments (Dillon et al. 2002; Wethington & Guralnick

2004; Wethington 2004; Dillon & Wethington 2004; Dillon et al. 2005; Wethington & Lydeard 2007)

have revealed that the family is not as species rich as previously reported (Te 1975; Te 1978; Te 1980;

Burch 1982; Burch & Tottenham 1980; Turgeon et al. 1998; Taylor 2003), but is in reality composed of a

few, phenotypically plastic species (Crowl & Covich 1990; Covich et al. 1994; DeWitt 1998; DeWitt et

al. 1999; DeWitt et al. 2000; Burnside 1998; Britton & McMahon 2004).

Recently it has been demonstrated that two physid species believed to be rare, threatened or endangered

are not genetically or morphologically separable from P. gyrina Say, 1821 (Taylor 2003; Wethington &

Guralnick 2004). However, other narrow range endemics such as P. zionis Pilsbry, 1926, long been

1


ecognized as morphologically distinct (Chamberlain & Jones 1929; Te 1975; Te 1978; Te 1980; Burch

1982; Burch & Tottenham 1980; Taylor 2003), have been shown to be genetically unique (Wethington &

Guralnick 2004; Wethington 2004; Wethington & Lydeard 2007). Here, we examine the validity of Physa

natricina Taylor, 1988 using morphological methods.

Physa natricina was described as a narrow range, endemic species from recent material collected from

Idaho and from fossil material collected from Idaho, Utah and Nevada (Taylor 1988). Recent material

came from the Snake River in Gooding, Elmore and Owyhee counties, Idaho (Taylor 1988). Taylor (1988)

reported P. natricina as fossils in Pleistocene/Holocene deposits from Bear Lake (Idaho/Utah) and Lake

Bonneville (Nevada/Utah), from Box Elder County and Salt Lake County in Utah and from Caribou

County (Lake Thatcher) and the Snake River in Idaho. The United States Fish and Wildlife Service listed

the Snake River P. natricina (among other gastropod species) as an endangered species due to a decline in

the species’ range, which was attributed to manipulation of water by hydroelectric development and

project operations, water withdrawal and diversions, water quality degradation and inadequate regulatory

environmental protection mechanisms (USFWS 1992). The Snake River is part of the Columbia River

watershed. The Snake River starts in western Wyoming, heading south along the Idaho border, before

turning west, crossing Idaho and then turning north and crossing into Washington, where it joins the

Columbia River.

Taylor (1988) reported that he placed the holotype specimen at the Los Angeles County Museum (under

the accession number LACM 2256) and paratype material at the University of Michigan Museum of

Zoology, Ann Arbor (UMMZ 230241, 230262, 229272, 229273, 229301 and 229388) and the US

Geological Survey (USGS 22427, 22448, and 23193). Additional material is referenced under the

accession numbers W­2512 and W­2514 and without accession numbers; however no indication is given

as to where these specimens were deposited. Taylor (2003) included P. natricina with the polymorphic,

nearly cosmopolitan Physa acuta Draparnaud, 1805 in his new tribe Haitiini and genus Hatia. It should be

noted that on the whole, Taylor’s (2003) higher­level taxonomic revision of the Physidae has not been

supported by other analyses (Dillon et al. 2002; Wethington & Guralnick 2004; Wethington 2004; Dillon

& Wethington 2004; Dillon et al. 2005; Wethington & Lydeard 2007).

Materials and methods

We compared holotype and paratype material of P. natricina as deposited by Taylor (1988) with more

recently collected physids from the type locality (Snake River, Idaho), as well as with other species from

western North America.

Status of the type specimens

We contacted each museum mentioned by Taylor (1988) in order to view and examine both holotype and

paratype material deposited by him as Physa natricina. Taylor (1988) stated that the holotype (dry shell

and soft body preserved in ethyl alcohol) was deposited in the Los Angeles County Museum (LACM).

However, no such material was present. Eventually the holotype was found and examined, having been

deposited by Taylor in the California Academy of Sciences in San Francisco (CAS) in 1999 (accession

number 114­795) (It should be noted that to prevent confusion, CAS has sent the holotype and paratype to

LACM).

2


Taylor (1988) claimed that he deposited paratypes at the US Geological Survey (USGS) Western

Ecological Resource Center. However, the USGS claimed not to have any collections of mollusks and no

collections that used the numbering system reported in the original description. We were able to examine

the paratype material deposited in University of Michigan Museum of Zoology (UMMZ).

Additional Material Examined

The holotype and paratype specimens were directly compared with more than 1,500 Physa specimens,

preserved in ethyl alcohol collected between 1995 and 2007 (from approximately 7,000 samples) from

along a 233 mile stretch of the Snake River in Idaho [ranging between Lower Salmon Falls Dam (RM

573) and Cobb Rapids (RM 340)] by Idaho Power Company (IPC) and identified and analyzed by

EcoAnalysts, Inc. (Cazier & Myers 1996; Cazier 1997; Cazier 1999a; Cazier 1999b; Cazier 1999c; Cazier

Shinn 2001a; Cazier Shinn 2001b; Cazier Shinn 2001c; Cazier Shinn 2001d; Cazier Shinn 2001e; Cazier

Shinn 2002; Cazier Shinn et al. 2001), all deposited in the Orma J. Smith Museum of Natural History

(ALBRCIDA) in Caldwell, Idaho. This 233­mile river reach includes the entire reported recent range of P.

natricina as well as 100 miles up and down stream of that range. Samples were collected within each river

mile throughout this area and included both shallow water (shoreline) and deep­water habitats. Samples

were excavated using a venturi loop dredging apparatus. Deep­water samples were obtained by utilizing

SCUBA equipment. EcoAnalysts, Inc. only identified these Physa specimens collected by IPC to genus.

An additional 137 Physa were collected and preserved in ethyl alcohol from lateral tributaries along this

233 mile reach of the Snake River, including Middle Line Canal, the C. J. Strike Reservoir, Brown’s

Creek, Bennet Creek, King Hill Creek, Billingsley Creek, Cedar Draw, Rock Creek, Southside Canal and

Rockland Creek.

Character Analysis

Attention was focused on Taylor’s (1988) description of both shell and anatomical characters of Physa

natricina in our examination of the holotype, paratypes, and topotypes. The defining external characters

for P. natricina are: 1) shell with inflated body whorl (length x width measured using a stage micrometer);

2) planes of aperture and growth lines conspicuously oblique to axis of coil; 3) axial sculpture of crowded

raised threads (dense growth lines); 4) tentacle with a dense black core of melanin in distal half only; 5)

body otherwise nearly colorless (Taylor 1988, p.67). Additional characters given include: 6) in dorsal

view the animal is amber, as seen through the shell; 7) mantle digitations are three at the posterior angle of

the aperture and three or four at the parietal surface; 8) mantle collar, mantle and mantle skirt are pale

amber gray (Taylor 1988, pp.71, 72). Furthermore, Taylor (1988) described the penial complex as:

preputium having a preputial gland one­third the length of the preputium, with two pilasters internally;

penial sac proximally expanded and slightly longer than the preputium; extremely large pyriform

sarcobellum which is distally papillate.

All material collected from the lateral tributaries and one to three specimens of the material deposited in

ALBRCIDA were chosen from each population for dissection and examination of the penial morphology.

Care was made to use Physa from the ALBRCIDA collections that most closely matched the Physa

natricina description and holotype. Using Te (1978) as an initial phylogenetic framework, the material

was partitioned into taxonomic groups.

3


Results

Taylor (1988; 2003) stated that the diagnostic characters he used for P. natricina came from the holotype,

numerous paratype shells (the majority being fossil) and apparently only three living animals, one of

which Taylor dissected. However, Taylor’s diagnostic characters for the species P. natricina are not all

present in the paratype series:

1. “Shell with inflated body whorl”

The additional specimens from the Snake River vary in the form of the body whorl, from a broadly

inflated body whorl (length x width = 1:1) to a narrow body whorl (1.7:1). Photographs of the paratype

material provided by Taylor (1988, p. 68, Figure 6) reflect this same range of variation (compare 6d with

a, e, g, h and j).

2. “Planes of aperture and growth lines conspicuously oblique to axis of coil”

This was difficult to gauge in the recent material (both the holotype and our specimens), as the growth

lines sometimes varied from oblique to sub­parallel along the axis of growth or where animals had been

damaged. Furthermore, the vast majority of the fossil paratype specimens had all growth lines either

eroded nearly to obliteration or non­existent. The growth lines were never consistently conspicuously

oblique in any of the material, including the types.

3. “Axial sculpture of crowded raised threads”

This character varied extensively between animals and even on individuals. The paratype specimens

UMMZ­229301 are nearly smooth. Our material from the Snake River bore shells that are smooth, with

faint growth lines, with obvious raised threads or with two or all three character states on individual

specimens. One specimen (ALBRCIDA­14940) has dense, raised growth lines on the body whorl up to a

healed break. After the break, the growth lines are fine and more regularly spaced. A second specimen

from the same lot had the opposite arrangement.

4. “Tentacle with a dense black core of melanin in distal half only”

Since the paratype material consists of empty shells or dried carcasses and the holotype is shriveled in

preservation, this character could not be adequately evaluated in the types. Our Snake River material

contains specimens without pigment in the tentacles, with entirely pigmented tentacles, pigment in the

basal half, pigment in the distal half and one specimen (ALBRCIDA­26197) has one tentacle with

pigment in the basal half and one with pigment in the distal half.

5. “Body otherwise nearly colorless”

The dried corpses in paratype collection UMMZ­229273 are entirely black in color. This is probably an

artifact of drying. Our Snake River material ranged from entirely black, to lightly pigmented to entirely

colorless in and between individual collections.

6. “In dorsal view the animal is amber, as seen through the shell”

The paratype series includes combinations of thick shells as well as translucent shells. It is impossible to

see the animal through the thick shells. The animals appear grey, amber or black through the thin,

translucent shells. Both thick and thin­shelled specimens are present in all the recent samples.

4


7. “Mantle digitations are three at the posterior angle of the aperture, and three or four at the parietal

surface”

This character is nearly impossible to verify in the available material. Many of the mantle digitations are

so distorted by preservation that accurate assessment was not possible. However, the holotype appears to

have only two mantle digitations at the posterior angle of the aperture, contrary to the description.

8. “Mantle collar, mantle and mantle skirt are pale amber gray”

These structures varied from faintly to darkly mottled, pale gray to dark gray or black, or gray brown to

brown or amber in all Snake River material. The pattern varied extensively in and between individual

collections. In different individuals, mottling was reduced, limited to one area, or darker or lighter in

various areas. There was no consistency in this character.

Penial morphology was examined in 211 Physa specimens from the Snake River and tributaries. All

dissections revealed a Physa type b or type c penial morphology (following Te, 1978). Thirteen specimens

were of the Physa gyrina Say, 1921 group and 198 specimens were of the Physa acuta group.

Discussion

Only the holotype of P. natricina was found to match the description found in Taylor (1988), although it

did not match in the number of mantle digitations. None of the more than 1,500 specimens examined

during this study conformed entirely to the diagnostic characteristics given in Taylor’s (1988) description

of P. natricina. The shell and penial characters as described by Taylor (1988; 2003) for P. natricina are

not appreciably different from the original description reported by Draparnaud (1805) for P. acuta. The

shell characters of Physa acuta have been shown to exhibit substantial phenotypic plasticity with regards

to biotic (Crowl & Covich 1990; Covich et al. 1994; DeWitt 1998; DeWitt et al. 1999; DeWitt et al. 2000)

and abiotic (Burnside 1998; Britton & McMahon 2004) factors. As such, shell characters in this group are

not entirely reliable.

All live Physa reported as P. natricina are less than 5 mm (Taylor 1988; 2003) and therefore are probably

juveniles. Frest (1991; personal comment) believes that P. natricina is P. integra, a junior synonym of P.

acuta (Dillon et al. 2002; Wethington 2004; Wethington & Lydeard 2007).

The difference between the penial morphology for P. natricina and that of P. acuta is described by Taylor

(1988; 2003) but not in any quantitative or definitive way. Both species have penial morphology c as

defined by Te (1975; 1978; 1980). Taylor (2003) reported that the penial complex of P. natricina differs

from P. acuta with regards to preputium to penial sheath length, with P. natricina having nearly equal

ratios of the two structures and P. acuta having a muscular sheath only about 0.75 as long as its

preputium. Taylor’s comparison of the sarcobellum differs between P. natricina and P. acuta with P.

natricina having a very large pyriform shaped sarcobellum bearing a single terminal papilla and P. acuta

having a minute paplilla at the top of an elongate sarcobellum. The size of the preputial gland was also

different between the two species as described in Taylor (2003) with P. acuta having a relatively small

preputial gland near the proximal end of the preputium while P. natricina’s preputial gland covers nearly

half of the proximal end of the preputium. However, based on many dissections of P. acuta across its

geographical distribution, the penial morphology characters are variable with regards to preputial gland

size, preputium to musculature penial sheath ratio or the shape and size of the sarcobellum. All these

5


character states were present individually or together in different combinations (Te 1975; Te 1978; Te

1980; Wethington & Lydeard 2007; Wethington in prep.). Therefore, the morphological differences in

penial morphology reported in Taylor (1988; 2003) are not valid distinguishing features for P. natricina.

The results of this study demonstrate that the diagnostic morphological characters of the P. natricina

holotype are not unique to any Physa taxon and cannot be used to define the species. Penial morphology,

as defined by Te (1975; 1978; 1980) has been shown as a perfect predictor of phylogenetic structure,

fitting perfectly with molecular analyses (Wethington 2004; Wethington & Guralnick 2004; Wethington

& Lydeard 2007). The penial characters of the holotype and by Taylor’s diagnoses are identical with the

widespread species Physa acuta. This character was consistent between the P. natricina holotype and all

P. acuta examined in this study. All the specimens collected from the Snake River system where the

penial morphology was examined were either P. acuta or P. gyrina. Therefore, we conclude that P.

natricina is a junior synonym of P. acuta.

While it could be argued that P. natricina did exist as a real species, but has since gone extinct due to the

habitat being invaded by P. acuta, we feel that this is extremely unlikely. First, fossil P. acuta are known

from all the same localities and more where fossil P. natricina was reported (Taylor 1988). Secondly and

more importantly, as shown above the characters of the type series, including the holotype are not unique,

do not conform to the original description and can be found in any of a myriad combinations across the

range of P. acuta, not just regionally, but globally. Because the definition for P. natricina is not specific

(i.e.: exclusive) it cannot be a species.

Acknowledgments

We thank the Orma J. Smith Museum of Natural History, Idaho Power Company, Los Angeles County

Museum, California Academy of Sciences for providing material. We acknowledge the following funding

sources: NSF (awarded to Lydeard, Dillon and Strong); Conchologists of America and Western Society of

Malacologists (awarded to Wethington); the University of Alabama Graduate Association and Biology

Department and the Multi­User Equipment Grant from NSF (awarded to Lydeard, Mayden, Powell and

Harris (DBI­007­351). R. Dillon and W. Clark provided valuable comments to earlier drafts. We are very

grateful to the following individuals who provided additional material: C. Albrecht, R. Anderson, C.

Appelton, P. Bouchet, L. Bousset, D. Britton, R. Bromley, P.­A. Crochet, R. Dillon, A. Estoup, B. Facon,

G. Feulner, R. Rojas Garcia, R. Guralnik, P.­Y. Henry, B. Howells, B. Isham, P. Jarne, H.A. Jambari, M.

Glaubrecht, M. Kawata, A.V. Korniushin, C. Lively, M. Malaquias, E. Michel, F. Munoz, F. Nijokou, V.

Nuñez, J.­P. Pontier, M. Porter, A.M. Ramos, F. Reinhard, T. Smith, M. Stevens, S. Trouve, A. Tsitrone,

M.J. Wallace, D. Wiegel, J. Wise and M. Zeki Yildirim.

References

Britton, D.K. & McMahon, R.F. (2004) Environmentally and genetically induced shell­shape variation in

the freshwater pond snail Physa (Physella) virgata (Gould, 1855). American Malacological

Bulletin, 19, 93–100.

Burch, J.B. (1982) North American freshwater snails: identification keys, generic synonymy,

supplemental notes, glossary, references, index. Walkerana, 1, 1–365.

6


Burch, J.B. (1989) North American freshwater snails. Malacological Publications, Hamburg, Michigan,

365 pp.

Burch, J.B. & Tottenham, J. (1980) North American freshwater snails: species list, ranges and

illustrations. Walkerana, 1, 1–215.

Burnside, C. (1998) Ecophenotypic variation in shell morphology within the freshwater pond snail genus

Physella (Pulmonata: Basommatophora) and its taxonomic implications. Dissertation, University

of Texas, Arlington, 206 pp.

Cazier, L.D. (1997) Middle Snake River Aquatic Macroinvertebrate and ESA Snail Survey. Annual Report

January 1996 – December 1996. Idaho: U.S. Fish and Wildlife Service. Report nr Section 10

permit PRT#799558. Idaho Power Company, Boise, 17 pp.

Cazier, L.D. (1999a) Bliss Powerplant Tailrace Biological Assessment. Partial annual report June 1999.

Idaho: U.S. Fish and Wildlife Service. Report nr Section 10 permit PRT#799558. Idaho Power

Company, Boise, 4 pp.

Cazier, L.D. (1999b) Middle Snake River Aquatic Macroinvertebrate and ESA Snail Survey: Idaho Power

Company. Responses to FERC Additional Information Request #40 a–c. FERC No. 2777, FERC

No. 2061, FERC No. 1975, FERC No. 2778. Idaho Power Company, Boise, 220 pp.

Cazier, L.D. (1999c) Middle Snake River Aquatic Macroinvertebrate and ESA Snail Survey: Idaho Power

Company. Responses to FERC Additional Information Request #39 a–e. FERC No. 2777, FERC

No. 2061, FERC No. 1975, FERC No. 2778. Idaho Power Company, Boise, 220 pp.

Cazier, L.D. & Myers, R. (1996) Middle Snake River Aquatic Macroinvertebrate and ESA Snail Survey.

Annual report April 1995 – December 1995. Idaho: U.S. Fish and Wildlife Service. Report nr

Section 10 permit PRT#799558. Idaho Power Company, Boise, 26 pp.

Cazier Shinn, D. (2001a) Snake River Aquatic Macroinvertebrate and ESA Snail Survey: 1997. Annual

report January 1997 – December 1997. Idaho: U.S. Fish and Wildlife Service. Report nr Section

10 permit PRT#799558. Idaho Power Company, Boise, 22 pp.

Cazier Shinn, D. (2001b) Snake River Macroinvertebrate Survey: 1998. Annual report January 1998 –

December 1998. Idaho: U.S. Fish and Wildlife Service. Report nr Section 10 permit PRT#799558.

Idaho Power Company, Boise, 24 pp.

Cazier Shinn, D. (2001c) Ecology Studies and Biological Assessment on Snake River ESA Snails: 1999.

Annual report January 1999 – December 1999. Idaho: U.S. Fish and Wildlife Service. Report nr

Section 10 permit PRT#799558. Idaho Power Company, Boise, 40 pp.

Cazier Shinn, D. (2001d) Ecology Studies and Biological Assessment on Snake River ESA Snails: 2000.

Annual report January 2000 – December 2000. Idaho: U.S. Fish and Wildlife Service. Report nr

Section 10 permit PRT#799558. Idaho Power Company, Boise, 52 pp.

Cazier Shinn, D. (2001e) Ecology Studies and Biological Assessment on Snake River ESA Snails: 2000.

Annual report January 2000 – December 2000. Idaho: U.S. Fish and Wildlife Service. Report nr

Section 10 permit PRT#799558. Idaho Power Company, Boise, 41 pp.

Cazier Shinn, D. (2002) Snake River ESA Snail colony Evaluation, Additional Survey and Laboratory

Studies: 2001. Idaho: U.S. Fish and Wildlife Service. Report nr Section 10 permit PRT#799558.

Idaho Power Company, Boise, 22 pp.

Cazier Shinn, D., Foster, A. & Stephenson, M. (2001) Benthic Macroinvertebrates of Hells Canyon Boise:

Idaho Power Company. Technical report nr Appendix E.3.1–8. FERC No. 1971. Idaho Power

Company, Boise, 91 pp.

Chamberlain, R.V. & Jones, D.T. (1929) A Descriptive Catalog of the Molluscs of Utah. Biological Series,

Vol. 1, No. 1. The University of Utah, Salt Lake City, 73 pp.

7


Crowl, T.A. & Covich, A.P. (1990) Predator­induced life­history shifts in a freshwater snail. Science, 247,

949–951.

Covitch, A.P., Crowl, T.A., Alexander, J.E. Jr. & Vaughn, C.C. (1994) Predator­avoidance responses in

freshwater decapod­gastropod interactions mediated by chemical stimuli. Journal of the North

American Benthological Society, 13, 283–290.

DeWitt, T.J. (1998) Costs and limits of phenotypic plasticity: tests with predator­induced morphology and

life history in a freshwater snail. Journal of Evolutionary Biology, 11, 465–480.

DeWitt, T.J., Sih, A. & Hucko, J.A. (1999) Trait compensation and conspecialization in a freshwater snail:

size, shape and antipredator behavior. Animal Behavior, 58, 397–407.

DeWitt, T.J., Robinson, B.W. & Sloan Wilson, D. (2000) Functional diversity among predators of a

freshwater snail imposes an adaptive trade­off for shell morphology. Evolutionary Ecology

Research, 2, 129–148.

Dillon, R.T. Jr. (2000) The ecology of freshwater mollusks. Cambridge University Press, Cambridge,

United Kingdom, 509 pp.

Dillon, R.T. Jr., Wethington, A.R., Rhett, J.M. & Smith, T.P. (2002) Population of the European

freshwater pulmonate Physa acuta are not reproductively isolated from American Physa

heterostropha or Physa integra. Invertebrate Biology, 121, 226–234.

Dillon, R.T. Jr. & Wethington, A.R. (2004) No­choice mating experiments among six nominal taxa of the

subgenus Physella (Basommatophora: Physidae). Heldia, 6, 69–78.

Dillon, R.T. Jr., Robinson, J.D., Smith, T.P. & Wethington, A.R. (2005) No reproductive isolation

between freshwater pulmonate snails from Physa virgata and P. acuta. The Southwestern

Naturalist. 50, 415–422.

Draparnaud, J. (1805) Histoire Naturelle des Mollusques Terrestres et Fluviatiles de la France. Louis

Colas, Paris, France, 614 pp.

Frest, T.J. (1991) Letter dated 2 June 1991 to Jay Gore, containing a review of Beak and Pentec snail

surveys and studies. US Fish and Wildlife Service, Boise, ID, 16 pp.

Lydeard, C., Holznagel, W.E., Schnare, M.N. & Gutell, R.R. (2000) Phylogenetic analysis of molluscan

mitochondrial LSU rDNA sequences and secondary structures. Molecular Phylogenetics and

Evolution, 15, 83–102.

Remigio, E.A., Lepitzki, D.A.W., Lee, J.S. & Hebert, P.D.N. (2001) Molecular systematic relationships

and evidence for a recent origin of the thermal spring endemic snails Physella johnsoni and

Physella wrighti (Pulmonata: Physidae). Canadian Journal of Zoology, 79, 1941–1950.

Taylor, D.W. (1988) New species of Physa (Gastropoda: Hygrophila) from the western United States.

Malacological Review, 21, 43–78.

Taylor, D.W. (2003) Introduction to Physidae (Gastropoda: Hygrophila) biogeography, classification,

morphology. Revista de Biologia Tropical Vol. 51 Supplemental (1), 1–287.

Te, G.A. (1975) Michigan Physidae, with systematic notes on Physella and Physodon (Basommatophora:

Pulmonata). Malacological Review, 8, 7–30.

Te, G.A. (1978) The systematics of the family Physidae (Basommatophora: Pulmonata). Ph. D.

Dissertation, University of Michigan. 325 pp.

Te, G.A. (1980) New classification system for the family Physidae. Archiv für Molluskenkunde, 110, 179–

184.

Turgeon, D.D., Quinn, J.F., Bogan, A.E., Coan, E.V., Hochberg, F.G., Lyons, W.G., Mikkelsen, P.M.,

Neves, R.J., Roper, C.F.E., Rosenberg, G., Roth, B., Scheltema, A., Thompson, F.G., Vecchione,

M. & Williams, J.D. (1998) Common and scientific names of aquatic invertebrates from the

8


United States and Canada: mollusks. Special Publications, Vol. 26. American Fisheries Society,

Bethesda, Maryland, 526 pp.

USFWS (1992) Endangered and threatened wildlife and plants; determination of endangered or threatened

status for five aquatic snails in south central Idaho. Federal Register, 57, 59242–59257.

Wethington, A.R. (2004) Phylogeny, taxonomy and evolution of reproductive isolation in Physa

(Pulmonata: Physidae). Ph. D. Dissertation, University of Alabama, Tuscaloosa, 787 pp.

Wethington, A.R. & Guralnick, R. (2004) Are populations of physids from different hot springs distinctive

lineages? American Malacological Bulletin, 19, 135–144.

Wethington, A.R. & Lydeard, C. (2007) A molecular phylogeny of Physidae (Gastropoda:

Basommatophora) based on mitochondrial DNA sequences. Journal of Molluscan Studies, 73,

241–257.

9

More magazines by this user
Similar magazines