Warm spells in winter affect the equilibrium between winter phenotypes.

ABSTRACT

Each phenotype is a product of the interaction of the genes and the environment. Although winter phenotype in seasonal mammals is heritable, its development may be modified by external conditions. In today's world, global climate change and increasing frequency of unpredictable weather events may affect the dynamic equilibrium between phenotypes. We tested the effect of changes in ambient temperature during acclimation to short photoperiod on the development of winter phenotypes in three generations of Siberian hamsters (Phodopus sungorus). Based on seasonal changes in fur colour, body mass, and expression of daily torpor we distinguished three different winter phenotypes responding, non-responding, and partially-responding to short photoperiod. We found that warm spells in winter can increase the proportion of non-responding individuals in the population, while stable winter conditions can increase photoresponsiveness among the offspring of non-responders. We conclude that the polymorphism of winter phenotype is an inherent characteristic of the Siberian hamster population but the development of winter phenotype is not fixed but rather a plastic response to the environmental conditions.