Positive Allometry and Fitness Display: Intraspecific Scaling of Craniofacial Features in Adult Male Cercopithecoids.
详细信息
文摘
A body of literature on sexual selection and fitness signals supports intraspecific positive allometry of adult male secondary sexual characteristics when fitness and body weight are correlated. Relative overbuilding of a fitness signal functions in signaling body size and fitness to conspecifics and facilitates individual assessment by other competitive males and potential mates. Males with relatively larger fitness signals have a reproductive advantage over smaller males since male-male competition over mates often takes the form of ritualistic display and larger males can endure costs of producing and maintaining fitness signals. This represents the first test of the scaling theory in primates using highly dimorphic papionins known for social groups with intraspecific competition optimal for evolution of morphological fitness signals. Large samples of intraspecific adult males are utilized with emphasis on craniodental features including the canine tooth,the supraorbital torus and facial area and length. Features specific to a taxon are analyzed including the maxillary ridge in Mandrillus leucophaeus,M. sphinx and Macaca nigra as well as zygomatic area in Theropithecus gelada. Reduced major axis regression is used in allometric analyses against known body weights or size surrogates. Wild-shot body weights are available for Papio anubis,P. cynocephalus and Macaca fascicularis that are used to generate size surrogates in closely related taxa. Intraspecific samples of adult male Hylobates lar,Chlorocebus aethiops,Erythrocebus patas,and Nasalis larvatus are analyzed for control and comparative purposes. Positive allometry is demonstrated throughout features of the facial skeleton in Mandrillus sphinx and Mandrillus leucophaeus supporting strong sexual selection in these taxa. Support for the hypothesis in other large-bodied papionins is mixed and support for the hypothesis in small-bodied papionins is only found in Macaca nigra. Positive allometry of facial length appears to have a phylogenetic component as it is apparent in most African papionins but not in Asian papionins. Finally,non-papionins also exhibit positive allometric scaling in several craniodental features suggesting that fitness signaling is not specific to papionins； however,the monomorphic Hylobates lacks strong support for positive allometry. Results indicate variation in intraspecific selective regimes likely drive relative feature size in the male papionin face.