Behind the scene of body mass allometries

Abstract

I use data based life history models for 9,488 species of birds and 4,865 species of mammals to illustrate natural selection causes for the evolution of inter-specific body mass allometries. Each model integrates the growth and demography of individuals with the life history energetics and population ecology of the species. I show i) how the primary selection of resource handling and mass-specific metabolism generates the net energy of individuals, ii) how the selected net energy generates a population dynamic feedback selection where intra-specific interactive competition selects body masses that scale in proportion with net energy on the timescale of natural selection, iii) how the primary selection of metabolism selects an allometric curvature where the residual mass-specific metabolism--relative to the expectation of the mass-rescaling allometry--is an initially declining function of mass in terrestrial placentals and birds, but not in marsupials and bats, iv) how the selection of body mass buffers ecological variation in survival, and v) how the joint selection of mass and optimal foraging selects the exponents of body mass allometries from the dominant spatial dimensionality of the foraging ecology.