Discretising Keyfitz' entropy for studies of actuarial senescence and comparative demography

2023

1. Keyfitz’ entropy is a widely used metric to quantify the shape of the survivorship curve of populations, from plants, to animals, and microbes. Keyfitz’ entropy values 1 correspond to species with a decreasing mortality rate with age (negative senescence), and a Keyfitz entropy of exactly 1 corresponds to a constant mortality rate with age. Keyfitz’ entropy was originally defined using a continuous-time model, and has since been discretised to facilitate its calculation from discrete-time demographic data. 2. Here, we show that the previously used discretisation of the continuous-time metric does not preserve the relationship with increasing, decreasing, or constant mortality rates. To r…

The Demographic Costs of Sexually Antagonistic Selection in Partially Selfing Populations

2022

When selection differs between the sexes, genes expressed by both males and females can experience sexually antagonistic (SA) selection, where beneficial alleles for one sex are deleterious for the other. Classic population genetics theory has been fundamental to understanding how and when SA genetic variation can be maintained by balancing selection, but these models have rarely considered the demographic consequences of coexisting alleles with deleterious fitness effects in each sex. In this article, we develop a stage-structured Mendelian matrix model and jointly analyze the evolutionary and demographic consequences of SA selection in obligately outcrossing (i.e., dioecious/gonochorous) …

Does symmetry preclude the evolution of senescence? : A comment on Pen and Flatt 2021

2023