Allegheny Mountain dusky salamander COSEWIC assessment and status report: chapter 6

Distribution

Global Range

The global range of D. ochrophaeus is centred on the western slope of the Appalachian Mountain system in Eastern North America (Fig. 2) (Conant and Collins 1998; Petranka 1998). The distribution extends from the Adirondack Mountains of northern New York state, west to northeastern Ohio, and south through all of Pennsylvania except the southeastern quarter, northeastern Maryland, eastern and southwestern Virginia to eastern Kentucky, extreme western Virginia, south through the southern Blue Ridge Physiographic Section of eastern Tennessee, and western North Carolina to northern Georgia (Orr 1989; Conant and Collins 1998; Petranka 1998). In the northern part of its range, the species is apparently absent from Vermont and eastward; the only record for Vermont is questionable (M. Ferguson, Vermont Nongame and Natural Heritage Program, pers. comm.).


Canadian Range

Desmognathus ochrophaeus is widely distributed in eastern North America but reaches the limit of its range at the Canadian border. D. ochrophaeus was first found in Canada at Covey Hill, Quebec in 1988, but the species' identification was confirmed genetically, using isozyme electrophoresis, only in 1990 (Sharbel and Bonin 1992). An old record from the St. John River, New Brunswick (Logier 1952), was based on a misidentification (F. Cook, pers. comm.). Desmognathus ochrophaeus occurs in Quebec only in forested habitat on the north side of the hill known as Covey Hill (Fig. 3), at the northernmost edge of the Adirondack Mountains in extreme southwestern Quebec (45 º02'N, 73º47'E) (Sharbel and Bonin 1992). There is also a town in the area called Covey Hill, but throughout this report the term "Covey Hill" will refer to the hill unless otherwise noted. The area is situated almost directly south of Montréal and about 2-4 km north of the New York border. The Quebec distribution consists of 5 to 7 springs located roughly in a rectangle 3 km x 6 km encompassing the north side of Covey Hill, plus one site located 20 km farther west near the Mitchell brook at Franklin. Covey Hill is considered as one locality with a surface area of less than 50 km² and a potential species’ distribution of 100 km² (Alvo and Bonin 2003).


Figure 3: Canadian distribution of Desmognathus ochrophaeus in Niagara area, Ontario and Covey Hill, Quebec

Figure 3: Canadian distribution of Desmognathus ochrophaeus in Niagara area, Ontario and Covey Hill, Quebec.

Indicated by black circles.

Covey Hill is a geological sandstone formation which forms the Piedmont section of the Adirondacks (Alvo and Bonin 2003). The area is within the Appalachians’ division of Quebec and is a region of hardwood forest within the Canadian Mixedwood Plain Ecozone. Water from Covey Hill descends from the northernmost slopes of the Adirondack Mountains and flows into the St. Lawrence Valley, a region inhospitable to the species. Because the species broods and overwinters in high-elevation habitats, it is unlikely that populations will be found farther north of Covey Hill. Surveys conducted to the south of the known Covey Hill localities as far as the New York border have failed to yield the species (Bonin 1993). Sampling of stream salamanders has been carried out in potential habitat in other parts of the Piedmont, but was restricted to permanent streams and was therefore not appropriate for finding D. ochrophaeus. Sampling of appropriate habitat in the Eastern Townships, an area east of the known population and not in the Adirondacks, has thus far failed to find the species (J. Bonin, unpublished data). In view of its apparent absence from Vermont, Lake Champlain may be an eastern geographical barrier to its distribution.

In 1989 two Desmognathus salamander populations were found in the Niagara Gorge of Ontario (Kamstra 1991) and were both identified as Northern Dusky Salamanders (D. fuscus) based on their morphological features. A survey of these salamander populations by the Ontario Ministry of Natural Resources in September 2004, however, revealed that one of the two populations had morphological characteristics more often associated with D. ochrophaeus (rounded tails, straight dorsolateral stripes, and mid-dorsal chevron markings) than D. fuscus. Molecular analysis of tissue samples from three individuals in the population confirmed that they are D. ochrophaeus (Markle and Green 2005). This represents the first recorded instance of D. ochrophaeus in Ontario, and the only known population of this species within the province. Recent investigation of the 1989 Queenston site voucher, currently stored at the Royal Ontario Museum (ROM # 19813), has revealed that the specimen appears to be D. ochrophaeus based on morphological characteristics. It was originally misidentified as D. fuscus as reported by Kamstra (1991) (W. Weller and R. MacCulloch pers. comm.). A second voucher collected by Kamstra in 1989 is stored at the Canadian Museum of Nature (CMN # 31985) and remains identified as D. fuscus. Molecular analysis to confirm species type of either voucher is not possible due to preservation methods. The identity of the other population of Desmognathus salamanders within the Niagara Gorge (closer to Niagara Falls) was confirmed as D. fuscus based on molecular analysis (T. Markle unpubl. data).

The Ontario population is also within the Mixedwood Plain Ecozone and is located in an area of the Niagara Gorge north of Niagara Falls near Queenston (43º00’N, 79º00’E). The region is composed of deciduous forest (predominantly Sugar Maple, Acer saccharum) and is an extension of Carolinian forest, which acts as the extreme northern limit of many species whose central origins lie in the Carolinas of the United States. It is possible that the potential habitat of D. ochrophaeus within Ontario is restricted to moist gorge seep-type habitat along the Niagara River and Escarpment within Carolinian Forest habitat. The Niagara Gorge is a unique geographic area with many exposed geologic features caused by frequent erosion events over thousands of years. The entire distribution of the Niagara population occurs in only approximately 0.53 ha (= 0.0053 km2), and the whole population is found within the vicinity of a single cascade channel on a 77% slope gradient. The known distribution of this population is bordered by the Niagara River at the bottom of the gorge, and human development along the top of the cliff.

The range of this species in Canada is very restricted and represents only a very small portion of its entire global range (<1% of total distribution is in Canada). The Covey Hill and Niagara Gorge populations remain the only known populations of this species within Quebec and Ontario, respectively, despite numerous field surveys for stream salamanders conducted throughout both provinces (Weller 1977; Gordon 1979; Bonin 1989; Shaffer and Bachand 1989; Bider and Matte 1996; J. Bonin, pers. obs.; R. Tervo, pers. comm.). This species is not known to occur in any provincial parks or in any areas managed by the federal government (P. Achuff pers. comm.).


Designatable Units

The two known localities for D. ochrophaeus in Canada are each completely isolated from other parts of the species’ range. The Niagara gorge locality lies with in the Carolinian faunal province. The closest neighbouring populations are in the United States and are located along the Niagara Escarpment in New York State, 22 kilometres east across the gorge. No populations are currently known from within the Niagara Gorge on the New York side (A. Breisch pers. comm.). The Covey Hill locality is in the Great Lakes/St. Lawrence faunal province. It is approximately 90 km north of the closest known localities in upper New York State. Both localities face similar threats.

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