Chalmers Conferences, 9th European Conference on Mathematical and Theoretical Biology

Evolution of senescence in heterogeneous landscapes
Olivier Cotto

Last modified: 2014-06-09


The current theory of senescence is developed in a very simple ecological and
demographic context, with a unique population at equilibrium in a homogeneous
habitat. In the wild, species live in a variable environment in space
and time, where the assumption of equilibrium is often transgressed. In this
study, we use models of quantitative genetics in structured populations in
order to investigate the evolution of senescence in a variable environment.
Adaptation to local environment depends on phenotypic traits which expression
varies with age. We study dierent scenarios where the environment
changes abruptly, gradually or cyclically with time and where the environment
is heterogeneous in space with dierent populations connected by migration.
The strength of selection decreases with age, which predicts slower
adaptation of traits expressed late in the life cycle, potentially generating
stronger senescence in habitats where selection changes in space or in time.
This prediction is however complicated by the fact that the genetic variance
also increases with age. With numerical calculations, we found that in
most cases the rate of senescence is enhanced when the environment varies.
Especially, migration between dierent habitats is a durable source of senescence
in heterogeneous landscapes. We also show that the rate of senescence
can sometime decrease transiently, when the population is not at equilibrium,
with possible implications in experimental evolution and in the study
of invasive species. Our results highlight the need to study age-specic adaptation,
as a changing environment can impact dierently each age-class with
dierent consequences on demography.