Extreme color variation in marmots (Marmota) [Variation des couleurs extrêmes chez les marmottes (Marmota)].

Résumé

Albinism, melanism, or both occur in flaviventris, monax, baibacina, caudata, bobak and camtschatica. Non-albino white marmots occur in marmota, bobak and baibacina. "Blue" forms occur in bobak and pale yellow individuals are observed in flaviventris. The frequency and persistence of extreme color phases remains largely unknown, but it seems likely that they are uncommon and of short duration. However, melanism has persisted for at least 80 years in a flaviventris population at a frequency of 16 to 20 % and melanism occurs in about 25% of a bobak pohe population. These frequencies suggest that melanism in these populations has some selective advantage which is balanced by its costs. The color variants indicate that mutation occurs frequently in the melanism genes which produce color morphs on which natural selection could act. The ancestral color of the dorsal pelage apparently is shades of brown frequently marked with splotches or streaks of yellow, reddish-brown, white, or black. These patterns indicate that melanin concentrations vary locally, but any selective advantage of these patterns is unknown. Three species have a pelage that is predominantly white (caligata), gray (baibacina), or dark brown (vancouverensis). Given that white or melanistic forms occur at very low frequencies in normally brown-colored species raises the question of what selective factors led to the evolution of light- and dark-colored species. Because pelage color and quality markedly affect thermoregulation, studies of marmot fur and heat transfer are essential for understanding extreme color variations.