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A Model for the Evolution of Pinniped Polygyny

George A. Bartholomew
Evolution
Vol. 24, No. 3 (Sep., 1970), pp. 546-559
DOI: 10.2307/2406835
Stable URL: http://www.jstor.org/stable/2406835
Page Count: 14
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A Model for the Evolution of Pinniped Polygyny
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Abstract

It is proposed (1) that the evolution of pinniped polygyny can profitably be examined as an integral part of a complex adaptive suite including physiology, morphology, ecology, and distribution which has involved in relation to an amphibious mode of life, and (2) that the selective factors evolved in this behavioral evolution can be identified by analysis of the processes by which the breeding structure is annually re-established and maintained in the rookeries. Terrestrial parturition and offshore marine feeding appear to have been key determinants of the major adaptive features of pinnipeds, and also to have interacted with characteristics common to most mammals in such a way as to favor both polygyny and sexual dimorphism. A model is presented that starts with terrestrial parturition and offshore marine feeding, which together are unique to pinnipeds, derives from them a series of functions typical of polygynous pinnipeds, relates these to characteristics common to most mammals, and indicates the major feedback loops which have given selective impetus to the evolution of the polygynous breeding system. Key roles are assigned to gregariousness, and male exclusion. The roles of large size, fat deposits, sexual dimorphism, female reproductive patterns, and ontogenetic development are evaluated.

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