1Department of Biology, Yale University, New Haven, Connecticut
2Physiology Research Laboratory, Scripps Institution of Oceanography, U.C.S.D., La Jolla, California 92037.
Tóm tắt
Eutamias alpinus, E. speciosus, E. amoenus, and E. minimus are contiguously allopatric on the eastern slope of the Sierra Nevada, California. This paper is part of a study of the factors determining the lines of contact between these contiguously allopatric populations. Overlapping fundamental niches and overlapping realized niches indicate that competitive exclusion has occurred. Patterns of intra— and interspecific aggression are described for these four species. The aggressive dominance of alpinus and amoenus explain the limited realized niches of speciosus and minimus. Hypotheses regarding the evolution of the patterns of aggressive behavior observed in these species are suggested. Aggression has been selected for in alpinus and amoenus because of a seasonal, potentially limited food supply which is economically defendable. Aggression has not been selected for in minimus because it is not metabolically feasible to engage in aggressive interactions in the hot sagebrush desert. Aggressive behavior has not been selected for in speciosus probably because of predator pressure and the seasonal abundance of food in its habitat.
