GEOGRAPHICAL VARIATION IN ANTLER MORPHOLOGY OF ALASKAN MOOSE: PUTATIVE EFFECTS OF HABITAT AND GENETICS
We assessed antler size of Alaskan moose (Alces alces gigas) with respect to the geographic region and dominant vegetation community (taiga or tundra) from which they were harvested from 1968 to 1983. Our retrospective analysis indicated that moose from the Copper River Delta and Alaska Peninsula possessed the largest antlers, whereas those from southeast Alaska, USA, had the smallest antlers. Delta flood plains of the Copper River offer a rich food supply for moose, and browse on the Alaska Peninsula also is plentiful; both areas have mild maritime climates and longer growing seasons than tundra and taiga habitats in interior Alaska—large antlers in those moose populations likely were the result of superior nutrition. After controlling for age, antlers of moose from tundra communities were significantly larger than those inhabiting taiga. Willows (Salix spp.), which are an important food for moose, dominate braided rivers and associated riparian areas in tundra habitat, and provide a high-quality and stable food supply over time. Fire and subsequent successional changes dominate taiga landscapes, which results in a variable food supply that is sometimes low in quality and quantity. Again, forage abundance and quality likely play important roles in determining antler size for populations of Alaskan moose inhabiting those plant communities. Nonetheless, antlers of A. a. gigas from taiga regions in Alaska, USA, were larger than those of A. a. andersoni from similar habitat in northeastern Minnesota, USA, and Saskatchewan, Canada. In addition, moose from tundra habitat on the Seward Peninsula, Alaska, which have colonized that area within the last ~30 years from the boreal forest, possessed antlers intermediate in size between moose inhabiting taiga and tundra. Moreover, moose from forested areas of southeast Alaska, which have a unique mitochrondial DNA haplotype from other subspecies of moose, also had comparatively smaller antlers than other moose in Alaska. Those outcomes indicated that differences in antler size likely have a genetic in addition to a nutritional basis. We hypothesize that differences in antler size of Alaskan moose in relation to habitat may have genetic as well as nutritional underpinnings related to openness of habitat, but more research is needed. Finally, our results on antler morphology, in concert with information on pelage coloration and recent data on genetics, do not support hypotheses concerning a double migration, or eastern and western races of moose, forwarded to explain morphological variation in moose inhabiting the New World. Likewise, we reject the hypothesis that ecotypical differences are primarily responsible for morphological variation in subspecies of moose inhabiting North America.
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