Patera appressa ( Sa y , 1821 ) , an introduced land snail in Ontario , Canada ( Mollusca : Gastropoda : Polygyridae )

The geographic distribution and habitat of Patera appressa (Say, 1821) in Canada are described. This is a North American land snail native to the southern Appalachians but it has been known, since 1994, from a cluster of sites in Trenton, City of Quinte West, Ontario, where it is presumably introduced. It may no longer be extant at any of the known Ontario sites.

A major milestone in Canadian terrestrial malacology was reached with the publishing of the first book to attempt to describe and illustrate all introduced land snails and slugs in Canada (Grimm et al. 2010).How ever, because this book was predominantly an identification guide and due to space and other limitations, it did not include detailed distributional data.Among the species featured in the book was Patera appressa (Say, 1821) (Mollusca: Gastropoda: Polygyridae; Figure 1), which is known in Canada only from Trenton, City of Quinte West, Hastings County, Ontario (Figures 2 and 3).
Patera appressa is native to the southern Appalachians and specifically is known from southern Ohio, West Virginia, Virginia, eastern Kentucky, eastern Tennessee, North Carolina, and northeastern South Carolina, but there are additional records from other states as far west as Indiana and Oklahoma and north to Maryland (Hubricht 1985;Martin and Bergey 2013).
Although details of some collection events are now lost, we document as best as possible the known sites for Patera appressa at Trenton, City of Quinte West, Ontario, its only known location in Canada.We also clarify our reasons why we believe that this species is introduced to Canada.Among the many species of introduced terrestrial molluscs in Canada, this species is notable because it is a native North American species.Finally, we infer that populations are declining or now extirpated, with no live snails found since 2006.
Specimens of Patera appressa were observed or collected on several occasions between 1994 and 2014.
These collections have been deposited in the New Brunswick Museum (NBM), Saint John (New Brunswick), the Mollusc Collection of the Canadian Museum of Nature (CMNML), Gatineau (Quebec), and in the personal collection of RGF (Table 1).Although specimens were collected in 1994 by one of us (FWS) and given to the late F. W. Grimm, these were not located in his collection and it is possible he did not examine this material although he did identify the other molluscan collections from this project (Karstad et al. 1995).These have gone missing over the years since the species' initial discovery in Ontario.
Relative to the majority of Canadian land snails, shells of Patera appressa are rather large (14-18 mm wide; Grimm et al. 2010).Patera appressa has a noticeably flattened spire and is pale brown (Figure 1).There are fine but rather coarse transverse wrinkle-like riblets over the whole shell surface but strongest on the apical surface of the whorls; these riblets are much weaker on the basal surface so that to the unaided eye, the base appears smooth.Microscopic rows of minute papillae are scarcely evident in the best preserved shells.The umbilicus is entirely sealed in adult shells by a prominent white callus.There is a long, slightly curved, white tooth on the parietal wall.The baso-columellar lip of the aperture bears a ridge-like callus that truncates before reaching the palatal lip.No teeth are present on the palatal lip (Grimm et al. 2010).Among native and introduced snails in Canada, P. appressa is distinctive by having a more prominent, tubercle-like basal tooth, as well as a palatal tooth; the shell surface is microscopically granular under a hirsute periostracum.Neohelix dentifera is somewhat larger than P. appressa (>19 mm; Pilsbry 1940), with a slightly higher spire and a shorter parietal tooth.Xolotrema denotatum is also larger (>18 mm; Pilsbry 1940), with a prominent palatal tooth and closely, microscopically papillose shell surface under a scaly periostracum.
One of us (MJO) gave specimens to the late F. Wayne Grimm for identification, who reported it as "Patera cf.panselena [sic]" (Grimm 1996), a southern Appalachian endemic restricted to West Virginia, western Virginia, and extreme southeastern Kentucky.Grimm apparently had done some anatomical work on this material but was uncertain about his identification and seems to have thought it related to, but not the same as, P. panselenus (Hubricht, 1976).However, he left no detailed notes or other evidence to support this hypothesis.Pilsbry (1940) described and figured all taxa in the group then known.Hubricht (1976) described Patera panselenus (as Mesodon) and stated that it was most like P. perigrapta (Pilsbry, 1894) but with a more flattened shell and anatomically with a much shorter penis.Dourson (2010) described and figured all species in the group, including P. perigrapta and P. appressa.Patera perigrapta and P. panselenus have strong microscopic s pi ral striae; P. laevior (Pilsbry, 1940) has very weak spiral striae; and P. appressa has spiral rows of microscopic papillae (Pilsbry 1940;Hubricht 1976;Dourson 2010).We find that Canadian shells certainly do not exhibit the strong, deep spiral striae of P. perigrapta (see Pilsbry 1940: 755, Fig. 454d).In some of the best preserved shells we do and unlikely to be confused with any other species.However, the Canadian polygyrids that most resemble P. appressa by presence of a closed umbilicus, a long parietal tooth and depressed form are Inflectarius inflectus (Say, 1821), Neohelix dentifera (A.Binney, 1837) and Xolotrema denotatum (A. Férussac, 1821).The shell of I. inflectus differs from P. appressa by its smaller size and   1).The upper cluster of dots are within the Trenton Greenbelt Conservation Area; the lower cluster, on and near the northeast slope of The Mountain.Legend: red lines, roads; green, wooded areas; pink, residential areas; grey polygons, large buildings; blue, water.see rows of microscopic papillae, but this character is difficult to see in the majority of our specimens, many of which are worn.In Canada, Patera appressa is known since 1994 from at least 14 separate collecting events (frequently at the same sites) in Trenton, City of Quinte West, Hastings County, Ontario (Table 1) that could be regarded to represent two separate geographic locations.
The site described by Grimm as being on a "small island in [the] Trent River" (Table 1) probably refers to the original MJO site (TGCA, see below) because one has to cross a bridge to get to it, and we are doubtful that Grimm could have reached any of the actual islands in the Trent River.Grimm's second site (Table 1, record 6) could be at the same place, but we have no way to know.
The majority of collections were made along the west shore of the Trent River, between County Road 33 (Water and Front streets) and the river (Figure 2), within Trenton Greenbelt Conservation Area (TGCA), mostly along the Jack Lange Memorial Walkway.The TGCA is characterized by very disturbed habitat, within an urban-industrial setting.Patera appressa was found in shrubby, disturbed areas, some with exposed concrete remains from the former industrial use of the site (Fig- ures 3 and 4).Currently (2014), the site is a park, with a walking trail and mowed grass areas.Off-trail, the site remains much as it was in 1994, with shrubs and small trees, tall grass, and concrete "pavement".The area is underlain by limestone bedrock.
The second location is ca.800-1,000 m southeast on the northeast side of Trenton Mountain ("The Mountain" on 1:50,000 topographic maps (Centre for Topographic Information 2000), but called Mount Pelion locally), a drumlin hill park partially surrounded by residential neighbourhoods (Figures 2-6).Here, Patera appressa  : on or at the base of The Mountain and along the Trent River in the Trenton Greenbelt Conservation Area (TGCA).
* These numbers may not reflect the degree of abundance of Patera appressa at a particular site and date, but rather, these numbers only document the quantity of specimens collected and now catalogued and vouchered in collections.
Forsyth et al. | Patera appressa in Ontario, Canada was found on a wooded slope with Eastern White Cedar (Thuja occidentalis) dominant.Quantities of garbage were noticed on some occasions (Table 1).The slope is steep, approaching 45 degrees.Both of these sites would be classified as very disturbed (TGCA) to moderately to very disturbed (The Mountain) and had a mixture of native and introduced species (Table 2).At both sites, large numbers of Patera appressa shells have been found (Table 1), but abundance was not consistently recorded and numbers of specimens collected (or still in the collections available to us) may not accurately represent the abundance of the dead shells vs. living snails.Living snails were rarely found, except in the 1990s, with the last live individual collected in 2006 by MJO. In April 1994, at The Mountain on the only visit to the sites made during rainy weather, FWS noted dead shells and live animals clustered on rocks and logs in such numbers as to cover most of the surface.
Populations of introduced species are often characterized by large numbers of individuals, and the initial observations of this species at Trenton in 1994 and 1995, were that living snails were abundant.However, it is just as possible that the large number of old shells found at Trenton more recently were from several generations and not necessarily evidence of a huge population.Pearce (2008) suggests that shells may take 4-7 years to decompose to a state in which they are no longer identifiable and decomposition is even slower in limestone areas such as Trenton.Relatively large and sturdily constructed, shells of P. appressa are expected to remain in the environment for some time and the large number of dead shells could be cumulative of several generations and years.In recent years, fewer or no live snails and fresh shells have been found at the sites.In the most recent collections, shells were quite weathered, suggesting that the animals have been dead for some time.
These two sites are the only places in Ontario and Canada where Patera appressa is known to occur.From the point of view of species' conservation, it is important to know the status of this population.If it were native, it would be of high conservation value, but if it were introduced, which is what we think, it has little conservation value.
It is also worthwhile to discount the possibility that Wayne Grimm was responsible for introducing this population.Although he is known to have intentionally introduced populations of snails as "experiments" (Örstan et al. 2011), he never told us (FWS, MJO) that he was responsible for the Trenton population and was very puzzled and quite interested in the population when material was sent to him for study by us (MJO).
Patera appressa is mainly a southern Appalachian species (Pilsbry 1940;Hubricht 1985).Outside of this natural range, an established introduced population was recently found in Oklahoma (Martin and Bergey 2013).Other populations, which we presume could represent introductions, were reported decades ago from Indiana and eastern Maryland (Cahn and Kemp 1929;Webb 1942;Jackson 1950;Grimm 1959Grimm , 1971)).It was introduced to Bermuda prior to 1910 (Vanatta 1910;Pilsbry 1940), where populations continue to exist even today (Bieler and Slapcinsky 2000; Oldham and Forsyth unpublished data).Hubricht (1985), who did not distinguish between natural and introduced populations of this species, also recorded it from anthropogenic habitats (i.e., roadsides and urban areas).All of this information suggests a

Species
The Mountain  strong propensity as a "tramp species".Grimm (1996) thought that the Canadian population represented an extremely disjunct and probably introduced species and it was treated as introduced by Grimm et al. (2010).Given that the presumed native U.S. range is over 600 km to the south, we also believe that Patera appressa is not native to Canada.The disturbed, highly modified habitats at Trenton also suggest this.It is also interesting that P. appressa has not been found elsewhere in Ontario, which suggests that its introduction was a unique event and that further dispersal did not occur.The apparent absence of living individuals or fresh snails in recent years suggests that this species may no longer be extant at the known sites, although there remains the possibility that live snails have lately gone undetected.
Forsyth et al. | Patera appressa in Ontario, Canada

Figure 1 .
Figure 1.Five views of a shell of Patera appressa, from along the Trent River, Trenton, City of Quinte West, Hastings County, Ontario, Canada; NBM 009026; maximum diameter (width), 14.3 mm.

Figure 2 .
Figure 2. Trenton, Ontario, with sites (black dots) having geographic coordinate data mapped (see Table1).The upper cluster of dots are within Forsyth et al. | Patera appressa in Ontario, Canada

Figures 3- 6 .
Figures 3-6.Habitat of Patera appressa at Trenton.3: view from the top of The Mountain, looking north towards the Trenton Greenbelt Conservation Area (behind railway bridge in distance, left of the river).4: habitat of Patera appressa in one area (44.11017°N, 077.59061°W; September 2014) of the Trenton Greenbelt Conservation Area, showing concrete "pavement".5: near top of The Mountain (44.10256°N, 077.58597°W; September 2014).The trees, predominantly Eastern White Cedar, behind the building are at the top of a steep slope where weathered Patera appressa shells were found in 2014.6: wooded slope on The Mountain (44.10256°N, 077.58597°W; September 2014), immediately below area shown in Figure 5. Weathered Patera appressa shells were found here in 2014.

Table 1 .
Forsyth et al. | Patera appressa in Ontario, Canada Records of Patera appressa in Ontario, Canada.All records are at Trenton, within the City of Quinte West, Hastings County, in generally one of two areas (when known)

Table 2 .
Terrestrial Mollusca, other than Patera appressa, found at The Mountain and the Trenton Greenbelt Conservation Area."Y" means found; "Native" means to North America and Ontario.Forsyth et al. | Patera appressa in Ontario, Canada