Distribution of the middorsal stripe dimorphism in the wood frog, Rana sylvatica, in eastern North America

Abstract

The frequency of the middorsally striped morph of Rana sylvatica in Ontario and Manitoba varies from absence in southern Ontario to 80% on the coast of Hudson Bay, with a general value of 20–30% in the boreal forest, a rise to 50% on the forest–grassland ecotone in southern Manitoba, and a decline westward to 20% on the edge of the prairies. This morph is rare in the northeastern United States and Maritime Canada. The suggested relationship between its frequency and the "grassiness" of the background on which predators view it is reexamined, and it is suggested that a linkage with earlier transformation as demonstrated in Eurasian species may explain certain anomalies.

Genomic Analyses Reveal Association of ASIP with a Recurrently evolving Adaptive Color Pattern in Frogs

“…The vertebral stripe might increase concealment from visually oriented predators coming from above, such as birds or mammals which are more prevalent in terrestrial habitats, and thus confer a fitness advantage. A similar pattern is observed in several polymorphic species, where the incidence of the striped morph correlates with geographical or habitat features, with a greater proportion of striped individuals in more open habitats (e.g., Fishbeck and Underhill 1971 ; Stewart 1974 ; Schueler and Cook 1980 ; Tarkhnishvili and Gokhelashvili 1996 ). Interestingly, the vertebral stripe was lost significantly more often in arboreal lineages than in other groups, indicating a potential fitness cost of the pattern in this habitat, or that other color patterns are selected for and the vertebral stripe lost as a side-effect.…”

A Herpetological Survey of the James Bay Area of Québec and Ontario

“…In the most recent sizeable sample from Long Lake, 14% of breeding adults from 1997 were striped (22 of 154), the same frequency reported from there in samples from August of 1971 (the site described as "along highways in the vicinity of Cochrane," Schueler and Cook 1980). No Wood Frogs were actually seen around Moosonee in 2002; historically about 55% of the frogs from there are striped (1938-1939and 1971-1972, Schueler and Cook 1980: 1646. For comparison, about 2% in eastern Ontario and 2.5% in southwestern Québec are striped (FWS and JFD, unpublished data).…”

“…The mid-dorsal pale line, or stripe, is known to be relatively frequent in northern populations of Wood Frogs from Ontario and Québec, with respective frequencies of up to 76% and 45% reported (Schueler and Cook 1980). In 2002, 58% of the Wood Frogs observed in Québec were striped.…”

“…While the Leopard Frog is still common in southern Québec and Ontario, it suffered widespread declines in western Canada around 1976-1980(Koonz 1992Seburn and Seburn 2000). These declines happened in the populations from the Prairies, from Alberta to Manitoba, which are biogeographically linked to western James Bay populations by the possession of the Lithobates pipiens western mtDNA haplotype in some frogs from Attawapiskat, though those from Moosonee had the eastern haplotype (CMNAR 1971-1972specimens, Hoffman and Blouin 2004.…”