Forty years later : distribution of the introduced Heath Snail , Xerolenta obvia , in Ontario , Canada ( Mollusca : Gastropoda : Hygromiidae )

Xerolenta obvia is a Central European land snail that has been introduced to Ontario, Canada, where it was first recorded in the literature in 1975 from a single population at Bethany (City of Kawartha Lakes). Over the four decades since that publication, additional records have been found clustered near Bethany, within the City of Kawartha Lakes, neighbouring Peterborough and Northumberland counties, as well as the Regional Municipality of Durham. Two distant sites are also now known, one in rural Ottawa (southeastern Ontario), and one at Windsor, Essex County (southwestern Ontario).

of the village centre (Grimm and Wiggins 1975).For three decades, the only published North American record of X. obvia (then reported as Helicella obvia) was this Bethany population, but more recently, X. obvia has been found in the United States, first at Detroit, Michigan, in 2001 in a Canadian Pacific rail yard (Robinson and Slapcinsky 2005) and most recently in Cascade County, Montana (Montana Natural Heritage Program 2013).Xerolenta obvia is ranked moderately high in a list of terrestrial gastropod species that are potential major pests (Cowie et al. 2009).In the last several years, the continuing existence of the Bethany population has been confirmed (Grimm et al. 2010) and somewhat chance encounters of this species by biologists, naturalists, and landowners, have added several new records.As details of these occurrences are mostly unpublished, this paper reports the currently known sites of X. obvia in Ontario, which are also the only known sites in Canada.
New distributional data for this species were gathered over several years, either as a result of our own general field collections of terrestrial Mollusca or through our contacts with others (Table 1).Because of the disparate sources of these new records, data collection methodologies differ.
Voucher material is deposited in the mollusc collections of the New Brunswick Museum (Saint John, New Brunswick; NBM) (Table 1).
Xerolenta obvia is readily distinguished from all other snails in Ontario and not likely to be mistaken.The shell is relatively large (maximum diameter, ca.20 mm), flattened, smooth, and white or grey white, generally with a brown band above the periphery of

Notes oN GeoGraphic DistributioN
Figures 1 and 2. Xerolenta obvia aestivating on dead vegetation (knapweed, Centaurea sp. in Figure 1), Breezy Heights Road, Ottawa, Ontario.(Photographs by Aleta Karstad, Figure 1 and RGF, Figure 2).the last whorl and up to six brown, but often paler or interrupted, lines below (Figure 3).The apertural lip is not noticeably thickened or recurved.Reproductive anatomy of a specimen from Bethany was figured by Grimm and Wiggins (1975).Other publications useful for identifying this species include Kerney et al. (1983), Grimm et al. (2010), Welter-Schultes (2012), and Wiese (2014).Cepaea nemoralis (Linnaeus, 1758), a banded snail of similar size that is a widespread, abundant species over many areas of southern Ontario and common in Combining close (<1 km) and apparently connected sites, perhaps as many as 23 occurrences of Xerolenta obvia are known from Ontario.Some of the closest sites may be connected because X. obvia can tolerate and thrive in hot, dry, rocky, disturbed habitats that would normally be considered inhospitable and barriers to dispersal for other terrestrial snail species.Xerolenta obvia occurs across southern Ontario from Essex County in the west, east to the Ottawa region (Table 1; Figure 4).We discuss these occurrences in three groups as follows.

Essex County:
The westernmost record of Xerolenta obvia in Ontario is in the City of Windsor, Essex County.The occurrence was found by MJO in 2012 just south of the Black Oak Heritage Park, in an area of building rubble from a demolished light-industrial building surrounded by oldfield and shrubby growth.The site was highly disturbed in the past, and was transitioning to weedy old-field type plant species.This population is about 17 km southeast of the first known U.S. population in Detroit, Michigan.It is also within about 100 m of an active railway line and 175 m from the nearest road.Xerolenta obvia was very localized here, with thousands of empty shells and dozens or hundreds of live snails, but only within a very restricted area.This is the first southwestern Ontario record for this species.
City of Kawartha Lakes, Peterborough County, Northumberland County, and Durham Regional Municipality: The majority of records (about 21 discrete occurrences) of Xerolenta obvia in Ontario are from the City of Kawartha Lakes (formerly Victoria County) and Peterborough County (Figure 5).Our fieldwork often focused in the region surrounding the original Bethany site, and thus, there is a cluster of records around Bethany.The greater number of occurrences around the Bethany site than in other areas is therefore possibly due to greater search effort.If the Bethany occurrence was the only one present in the late 1960s and early 1970s it is plausible that other occurrences in the City of Kawartha Lakes, Peterborough County, Northumberland County, and Durham Regional Municipality originated from it or the farm just west of the village centre that was mentioned by Grimm and Wiggins (1975).
Farther from Bethany, known sites are more scattered, with the most distant one being ca.47 km away (Figure 4), but as there is much potential habitat along roads and in old fields in this area (and elsewhere in southern Ontario), we anticipate that more sites will be discovered.

City of Ottawa:
Along several kilometres of Highway 417 and adjacent roads in rural Ottawa (Figure 6), there is what probably is a single large occurrence of Xerolenta obvia (although the most southeastern site is separate from the others by >1 km; see below), the only one known in eastern Ontario.Highway 417 dissects this population.Repeated visits have allowed us to better understand the extent of this occurrence, which is large.We document it here so that any future changes in extent can be noted later.
Xerolenta obvia was first noticed by one of us (RL) in 2009 along the entire section of Breezy Heights Road, which once was Highway 17, from 45.3385° N, 076.1910°W to 45.3463° N, 076.2026°W, a distance of 1.25 km.The snails are on both sides of the road, with denselypopulated sections scattered at random throughout the length.Probably the densest part is at the extreme west end, where Breezy Heights Road turns southwest into Grainger Park Road.The entrance to and perimeter of the Breezy Heights Quarry, on the south side of the road, has many X.obvia.
Near the eastern end of Breezy Heights Road, there is a curving grassy strip leading east towards Highway 417; this was a former section of Old Highway 17 which was torn up during the construction of the new 417 freeway.Xerolenta obvia are present along the entire length of this strip, with a very dense population near the eastern end, mostly on tall dead White Sweetclover (Melilotus albus Medik.), sometimes >40 snails To the north of Highway 417, the road called Highway 17 also has Xerolenta obvia.This section of the old Highway 17 (Highway 417 replaced it as the main highway north of Ottawa) runs east from Arnprior, through Antrim, and makes a hard left onto Grants Side Road when it comes to the new highway.The snails start west of Grants Side Road, and continue to the corner, also exending about 0.5 km along a rough track which parallels Highway 417 on the north side, from 45.3495° N, 076.2059°W to 45.3441° N, 076.1955°W, again almost exactly 1 km.
One of us (FWS) has surveyed along Highway 417 and found X. obvia along 1.8 km of the southwest (eastbound) side of the highway proximal to the quarry, and present along 560 m of the northeast (westbound) side of the highway, across from the quarry.The range of the snails on the northeast side of the new highway, around the old two-lane Highway 17 where the new highway crosses its route, is offset 410 m northwest from that on the westbound (quarry) side.There is no obvious habitat limitation to the range on either side of the highway (note that all these distances are straight-line, and that the road curves a little, and is about 70 m wide here).
In September 2014, RGF found Xerolenta obvia along the roadside of Panmure Road, just northeast of the Highway 417 interchange.This is about 1.9 km eastsoutheast from the closest record along Highway 417 (at the old roadbed).We do not know if this site is disjunct from, or continuously connected to, the main presence of the species to the west-northwest.FWS observed no X.obvia at one site approximately midway along Highway 17.
Xerolenta obvia is a calciphile that lives in Ontario in open, dry, grassy sites along roads and railways, and in fallow fields.In central Europe, where it is also found in vineyards, around ruins, in dunes, and on walls, X. obvia is largely synanthropic (Kerney et al. 1983;Welter-Schultes 2012).One characteristic of most populations of this species is the large numbers of snails and dead shells; populations can be large, sometimes covering several hectares.This seems not to be the effect of a population explosion of an unchecked introduced species but rather is normal for the species.Dense colonies of snails are typical within the native (or nearnative) range of the species in Europe as well (Pfeiffer 1841;Welter-Schultes 2012).
Large numbers of dead shells usually litter the ground once a population is established.A study in Greece reported that Xerolenta obvia live for one or two years, depending on climatic conditions, and die soon In some cases, snails were found in areas between points shown on the map.For example, the entire length of the old Highway 17 roadbed had X. obvia.It is unknown if the single record from Panmure Road (in a white circle), northeast of Highway 417 is connected to the other sites as a continuous distribution.after reproducing (Larazidou and Chatziioannou 2005).Thus, as a relatively large-shelled species with a short live span, large numbers of dead shells are present and readily noticeable.Shell of other terrestrial snail species may persist for one or more years, or even longer on calcareous ground (Pearce 2008), so that it is possible that the large number of shells of X. obvia is cumulative over several generations and years.
Xerolenta obvia aestivates on the stems of tall plants.While occasionally on dry grass stems, snails seem to favour much stronger dried plants and at the Ottawa location were almost always on these, especially White Sweet-clover, knapweed (Centaurea sp.), Queen Anne's Lace (Daucus carota L.), and Chicory (Cichorium intybus L.).
Although we cannot be certain that there were not other populations of Xerolenta obvia around southern Ontario during the 1970s when this species was first noticed, it is probable that over the last four decades the species has spread.The usually dense populations, apparently persisting dead shells, and the tendency of snails to aestivate well off the ground on the stems of plants (Figure 1) make this species especially conspicuous, and as a relatively large-bodied snail, it would be a prime candidate for citizen science-based monitoring.It seems likely that Xerolenta obvia will continue to expand its range in southern Ontario.

Figure 4 .
Figure 4. Distribution of Xerolenta obvia in Ontario.White circle = first recorded site at Bethany, City of Kawartha Lakes.Red square = Detroit, Michigan, USA population.County or equivalent county-like divisions where X. obvia is recorded are yellow-green.Rectangle = area of coverage of Figure 5. Abbreviations: ES, Essex County; DR, Durham Regional Municipality; KL, City of Kawartha Lakes; NO, Northumberland County; PE, Peterborough County; OT, City of Ottawa.

Figure 5 .
Figure 5. Presence of Xerolenta obvia in City of Kawartha Lakes, Peterborough County, Northumberland County, and Durham Regional Municipality, Ontario, Canada (boundaries marked by yellow lines), with some additional negative records (by one of us, FWS) shown.Black square = present; white square = absent.Arterial highways and roads are red; lesser roads are grey; trails are brown; railways are purple.
Forsyth et al. | Xerolenta obvia in Ontario, Canada similar areas and habitats, might be confused by those with little experience in recognizing terrestrial snail species.Shells of C. nemoralis are mostly straw-yellow, pinkish, or brown, with or without brown bands.The apertural lip, which is purple-brown, is thickened and recurved in adults.The umbilicus is closed in adults.