Geographic Variation in Body Size and Weight

ABSTRACT. Multiple range test comparisons of wing, tail, and net body weight measurements of 2,600 willow ptarmigan (Lagopus lagopus) specimens collected in Alaska and adjacent Yukon Territory showed statistically significant differences among populations from different geographic areas but also indicated surprising uniformity within populations designated as recognizable subspecies. Previous range distributions based on summer plumage colour and size of bill separated L. 1. aluscensis from L. 1. ulbus at the Alaska-Yukon border. On the basis of our measurements, it is believed that the population of the larger L. 1. alascensis extends eastward into Yukon Territory at least to Old Crow whereas the smaller L. 1. albus extends westward into Alaska in the upper Tanana River Valley and south of the Alaska Range to the Susitna River. It is suggested that the present dis-tribution of the various subspecies of willow ptarmigan in Alaska may be explained in part by their distribution at the time of Wisconsin glaciation and their subsequent dispersal. RESUME. Variations gkographiques de la taille et du poids du LagopPde des saules. De multiples comparaisons de mesures des ailes, de la queue et du poids net de 2,600 specimens de lagopkde des saules (Lugopus lagopus) recueillis en Alaska et dans la partie adjacente du territoire du Yukon, ont demontre des diffkrences statis-tiquement significatives entre les populations des diffkrentes aires gbographiques, mais ont aussi indiquk une surprenante uniformit6 parmi les populations d6signbes comme sous-espkces reconnaissables. L e s prkc6dentes distributions d‘habitat, bas6es sur la couleur du plumage et la taille du bec, distinguaient L. 1. alascensis de L. 1. albus B la frontikre Alaska-Yukon. Sur la base des nouvelles mesures, on croit que la population du L. 1. alas