Morphological Color-Change in the Red-Backed Salamander (Plethodon cinereus) While Kept in Captivity

Coloration is a trait frequently cited as important to ecological, and thus evolutionary, processes in amphibians. To fully understand the impact of coloration, a consistent method of color measurement is required, which is often achieved by collecting color information in a captive, laboratory setting. However, results from the lab can only be generalized to the field if coloration remains consistent between the two. In this study we collected spectral data from two discrete color morphs of Plethodon cinereus (erythristic and striped) at two distinct time periods while in captivity to determine whether and how their coloration changed over time. We found that brightness in both color morphs decreased similarly through time, though the change was most pronounced in the erythristic morph. Additionally, we examined the overall coloration change over time using multivariate change vectors and found that the magnitude (amount) of multivariate color change was significantly greater in the erythristic morph as compared to the striped morph (for cheek color patches). Intriguingly, the direction of color change in color space was oriented similarly among measured regions within each morph, whereas the direction of color change differed between morphs, indicating that while coloration changed for all individuals, how that change occurred was morph-specific. We propose a physiological mechanism that may be responsible for the observed changes, and suggest several additional mechanisms that may influence labile coloration in these salamanders. Additionally, our findings suggest that quantifying color from individuals held in captivity should be used with caution, as color changes observed in a laboratory setting may not reflect what is seen in the field.