Phenotypic dynamics, heterogeneity and the evolution of senescence

Background/Question/Methods

Evolutionary theories of senescence mostly rely on the intuition that derives from Hamilton's famous equations that describe the fitness consequences of changing survival and reproducion. But predictions from these theories do not account for many features of life histories. Also they do not speak to the maintenance of phenotypic variation in populations, at least partly because they lead to a primarily adapative view of life histories as being in some sense optimal.

We present new theory that shows how phnoptypic variation is maintained within populations, and how stochastic processes play a key role in the structure and fitness of life histories.

Results/Conclusions

We show that life history evolution is clearly tied to the stochastic dynamics of individual phenotypes over time. Patterns of senescence reflect the way in which individuals move among phenotypic states through their lives. The transition rates among stages reflect both fundamentally stochastic changes over each life but are also a likely target for evolution. Variation among life histories that is neutral in an evolutionary sense can maintain huge amounts of variation between individuals in their performance. We argue that this perspective leads to a fundamentally new way of thinking abouit life history evolution.