Southern flying squirrel (Glaucomys volans) COSEWIC assessment and status report: chapter 5
Update
COSEWIC Status Report
on the
Southern Flying Squirrel
Glaucomys volans
Atlantic (Nova Scotia) population
Great Lakes Plains population
in Canada
2006
Species Information
Dolan and Carter (1977) identified 10 subspecies. The only subspecies occurring in Canada is G. v. volans. The other subspecies occur entirely in the southern United States, Mexico and Central America.
Southern flying squirrels (Glaucomys volans) are small, nocturnal arboreal tree squirrels with soft, greyish-brown fur on the back and sides and pure white belly hairs. When gliding, squirrels are supported by a furred patagium extending from the wrists to the ankles. The tail is dorso-ventrally flattened and assists with in-flight steering and landing.
Distinguishing southern flying squirrels from northern flying squirrels (Glaucomys sabrinus) is difficult without live specimens in the hand or good photographs. Size (body mass and length of hind foot), colour of ventral fur and tail morphology are the main distinguishing features (Table 1). Tail shape is most noticeable when a flying squirrel has landed on a tree and the lighter-coloured tail is contrasted against the dark trunk of the tree. Petersen (2004) developed a molecular screen that utilized restriction enzyme digestion of the cytochrome-b gene to generate species-specific patterns.
Sightings by non-experts in areas of known or suspected sympatry should be considered “generic”. Despite the closeness in overall physical appearance, northern and southern flying squirrels are distinct species (see Arbogast 1999) and there is no record of their interbreeding (Dolan and Carter 1977; Wells-Gosling and Heaney 1984; Wells-Gosling 1985).
| Characteristic | Southern Flying Squirrel | Northern Flying Squirrel |
|---|---|---|
| base of ventral fur | white | grey |
| dorsal and lateral pelage | greyer, less rich than northern flying squirrel |
brown |
| mass | 47 – 85 g (pregnant females may approach 100 g (Adams 1995)) |
70 – 140 g |
| total length | 200 – 260 mm | 245 – 370 mm |
| tail length1 | 93.5 mm | 120.7 mm |
| tail shape | tapers base to tip | no taper, tail sides parallel |
1 Data for Nova Scotia and Ontario flying squirrels only (Lavers 2004)
Arbogast (1999) identified three main mtDNA lineages for Glaucomys spp.: two for G. sabrinus (“eastern”, including all of Canadian and “western”), and one for G. volans. G. volans was found to have diverged from the eastern G. sabrinus lineage some 0.7–1.3 million years ago. Little sequence variation was found across the range of G. volans in North America (Arbogast 1999). The evolution of the southern flying squirrel was influenced by glacial successions and coniferous and deciduous forest distribution (Arbogast 1999).
There is little evidence of genetic structuring of populations of southern flying squirrels in Ontario. Bednarczuk (2003) assessed several characteristics using microsatellite DNA markers for three Ontario locations: Point Pelee National Park (PPNP) (reintroduced in 1993 from Norfolk County), Norfolk County and Minden. Bednarczuk (2003) found low genetic differentiation among all three subpopulations (Table 2).
| Subpopulations compared | FST |
|---|---|
| Point Pelee National Park vs Minden | 0.0539 |
| Point Pelee National Park vs Norfolk | 0.0252 |
| Norfolk vs Minden | 0.0113 |
Source: Bednarczuk (2003).
Low subdivision (FST = 0.0314) was detected across 11 HN woodlots, suggesting a panmictic subpopulation. Estimated mean expected heterozygosity (HE) and observed heterozygosity (HO) based on four microsatellite loci were: 0.7934 and 0.7233 respectively for PPNP; 0.8356 and 0.7712 for Norfolk; and 0.7655 and 0.7500 for Minden. Similarly, moderate to high heterozygosities for seven microsatellite loci were reported for a population of southern flying squirrels in South Carolina (Fokidis et al. 2003). Bednarczuk (2003) also documented a low average pair-wise sequence divergence of 0.0045 between unique cytochrome-b haplotypes of five Ontario subpopulations (PPNP, Norfolk, Minden, Hamilton and Peterborough).
Petersen (2004) investigated geographic variation and phylogeography in G. volans in Nova Scotia using the mtDNA cytochrome-b gene and the control region (CR). Samples from Nova Scotia (NS), Ontario and the United States were undistinguishable displaying a low cytochrome-b sequence divergence of 0 – 2.1%, suggesting rapid post-glacial expansion in the Great Lakes Plains and Atlantic populations.
However, the control region exhibited higher rates of divergence (Petersen 2004). Average pair-wise sequence divergence of NS samples (n= 53) was 0.1±0.3%; 2.5±0.5% in the Ontario samples (n = 13); 2.1±0.5% between NS and Ontario samples; and 6.1±1.4% between NS and the United States samples (n = 1). Thirty-one CR haplotypes were identified in the overall Canadian G. volans samples, twenty of which were unique to 53 NS individuals. Two of the NS haplotypes were common occurring in 58.5% of the NS samples, another four haplotypes were identified in more than one individual, and the remaining 14 haplotypes were found in one individual only. Haplotypes were not shared between Ontario and NS. The lack of shared haplotypes between Ontario and NS G. volans, and the two common NS haplotypes suggest a significant loss of genetic variability by the NS population. G. volans was likely isolated in NS about 8000 years ago at low population numbers resulting in the significant loss of genetic variability. The population then experienced a range expansion period approximately 2000 years ago (Petersen 2004). These results may also be indicative of NS G. volans population diverging from Ontario populations. However, larger Ontario haplotype samples are required for a more robust analysis.
The two designatable units are based on a major range separation and different ecozones for southern flying squirrels in Canada: Great Lakes Plains and Atlantic populations. The Great Lakes Plains population occurs in southern Ontario and southwestern Québec, primarily within the Carolinian and Great Lakes / St. Lawrence faunal provinces. It accounts for the majority of southern flying squirrels in Canada.
The Atlantic population is limited to southern Nova Scotia, in the Appalachian / Atlantic Coast faunal province. It is isolated from all other G. volans population in Canada and the United States. Genetic work by Petersen (2004) suggested that southern flying squirrels are one of a number of species found in southern Nova Scotia isolated from the main part of their species’ range (see also Pielou 1991; Davis and Browne 1996). These species spread north following the retreat of the Wisconsin glaciers during an intermittent warming period, then became isolated following subsequent cooling. The Atlantic and Great Lakes Plains populations differ both genetically (Petersen 2004; see Genetic description) and phenotypically (Lavers 2004).
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