Generation time, net reproductive rate, and growth in stage-age-structured populations.
Major insights into the relationship between life-history features and fitness have come from Lotka's proof that population growth rate is determined by the level (expected amount) of reproduction and the average timing of reproduction of an individual. But this classical result is limited to age-structured populations. Here we generalize this result to populations structured by stage and age by providing a new, unique measure of reproductive timing (Tc) that, along with net reproductive rate (R0), has a direct mathematical relationship to and approximates growth rate (r). We use simple examples to show how reproductive timing Tc and level R0 are shaped by stage dynamics (individual trait changes), selection on the trait, and parent-offspring phenotypic correlation. We also show how population structure can affect dispersion in reproduction among ages and stages. These macroscopic features of the life history determine population growth rate r and reveal a complex interplay of trait dynamics, timing, and level of reproduction. Our results contribute to a new framework of population and evolutionary dynamics in stage-and-age-structured populations.
Max-Planck Odense Center on the Biodemography of Aging, Department of Biology, University of Southern Denmark, 55 Campusvej, 5230 Odense, Denmark; and Institut national de la santé et de la recherche médicale U1001, 24 rue du Faubourg Saint-Jacques, 75014 Paris, France.
Ulrich K
UK
Steiner
Shripad
S
Tuljapurkar
Tim
T
Coulson
D000818:Animals; D005075:Biological Evolution; D008954:Models, Biological; D011158:Population Growth; D012098:Reproduction / Q000502:physiology*; D012641:Selection, Genetic; D013997:Time Factors