Erin Petruzzi (2005). The role of thermal niche selection in maintenance of a colour polymorphism in Plethodon cinereus. MS Thesis, University of Akron, Ohio, (Moorei).

Abstract:
In eastern North America two common colour morphs exist in most populations of redback salamanders (Plethodon cinereus).  Previous studies have indicated that the different morphs may be adapted to different thermal niches and the morphological variation has been linked to standard metabolic rate at 15∞ C in one population of P. cinereus. This study tested the hypothesis that a correlated response to selection on maintenance metabolic rate (MMR) across thermal niches maintains the colour polymorphism in P. cinereus. We found that the two colour morphs sometimes differ in their (MMR) profiles. Field censuses showed that the two colour morphs are sometimes found at different substrate temperatures and that this difference is dependent on census location and season. Since these morphs differ in their maintenance energy expenditure, they may also differ in relative fitness. However, the differences in MMR profile in this study are not consistent, and when present do not indicate the existence of multiple thermal niches. Our results are therefore not consistent with maintenance of the polymorphism via a correlated response to selection across multiple niches.

Full Thesis on file at UA.