. The Canadian field-naturalist. 352 The Canadian Field-Naturalist Vol. 104 .0- ^ UJ I- z UJ a: O li- -. "T" 10 15 20 25 30 35 40 45 PLASTRON FIGURE AREA (cm2) Figure 4. The relationship between plastron figure area and figure intensity in Chrysemyspicta based on all specimens. The coefficients are intercept = and slope = The dashed line represents the intensity of the plastron background colour. Therefore points below the dashed line represent plastron figures darker than the plastron. 2). Low seam disalignments, wide laminar margins and reduced plas
. The Canadian field-naturalist. 352 The Canadian Field-Naturalist Vol. 104 .0- ^ UJ I- z UJ a: O li- -. "T" 10 15 20 25 30 35 40 45 PLASTRON FIGURE AREA (cm2) Figure 4. The relationship between plastron figure area and figure intensity in Chrysemyspicta based on all specimens. The coefficients are intercept = and slope = The dashed line represents the intensity of the plastron background colour. Therefore points below the dashed line represent plastron figures darker than the plastron. 2). Low seam disalignments, wide laminar margins and reduced plastron marking are all C. p. picta attributes, the presence of these characterisitcs in the Pike River population suggests the C p. picta influence extends from the south to at least the northern end of Lake Champlain. Reference to the three Montreal area localities (2,3,4) suggests that the C. p. picta influence extends to this region as well. These localities show a greater degree of variation in seam disalignment, tend to have wider scute borders and smaller plastron figures than the localities west of the Montreal region. If, as postulated by Bleakney, C. p. marginata arrived in the region of the New England seaboard via the Mohawk and Hudson Rivers during its postglacial dispersal, and hybridized with C. p. picta, it is equally likely that the C. p. picta genome may have spread northwest via the Hudson River and Lake Champlain system to the Richelieu and St. Lawrence Rivers. Because of the presence of C. p. marginata characteristics in Chrysemys populations from New Brunswick and Nova Scotia (Bleakney, 1958) and C. p. picta attributes in western Quebec (this study), Chrysemys populations in eastern Canada and the northeast- ern United States should be considered a mixed assemblage showing characteristics of both subspecies. In turn, the breadth of this zone of intergradation calls into question the utility of the idea that C. p. marginata is a distinct subspecific entity, ra
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