HABITAT AND THE EVOLUTION OF SOCIAL AND REPRODUCTIVE-BEHAVIOR IN CALLITRICHIDAE

The numerous remarkable traits characterizing the ecology and behavior of callitrichids have inspired considerable research and discussion o f the flexible mating system (cases of monogamy, polygyny, and polyand ry), cooperative breeding, reproductive inhibition by dominant females , rapid reproductive rate, significance of dietary differences (gum fe eding, frugivory, and insectivory), and demographics and social charac teristics of the four genera, Cebuella, Callithrix, Saguinus, and Leon topithecus. The majority of functional explanations evaluate costs, be nefits, and alternative strategies but do not address the critical sel ective forces that led to the behaviors in the first place. In this pa per, it is argued that Callithrix and Saguinus evolved to occupy a sma ll insectivore/frugivore niche in secondary growth forest patches (gap s arising from tree falls), and other successional forests and edge ha bitats; that Cebuella evolved to occupy a gum-feeding/insectivore nich e in inundated forest; and that Leontopithecus is above all a small an imal predator/frugivore and a mature forest genus. The keys to explana tions concerning the evolution of the social and reproductive systems of these animals lie in an understanding of the resource base in these different habitats. Finally, it should be remembered that studies of callitrichids have in the main part been carried out in habitats highl y altered by human activities (especially the Brazilian Atlantic fores t, home to marmosets and lion tamarins) and are not the environments i n which their social and breeding behavior evolved. (C) 1996 Wiley-Lis s, Inc.