Non-senescence in Neoclassical Growth Theory Notes go here.

Personal Background Decision consulting Livelihood Research Energy economics & climate change Legal theory (Law of Evidence) Evolutionary Biology Research objective: Provide academic practitioners with practical tools that meet exacting theoretical standards Motivation: Curiosity

AGENDA The Model Reznick Results Non-senescence

The model: Assumes populations consist of distinct genotypes with different traits that affect intrinsic lifespan. Assumes heritability of these traits is imperfect. Adheres to the formalities of Dynamic Systems Theory. Operates in two dynamic modes: Mode 1: mutation accumulation (purely deleterious mutations) Mode 2: genotypes select different fecundity/lifespan tradeoffs under a metabolic budget constraint

“Maintenance Investment Program” The dynamic modes: Genotype choice of “Maintenance Investment Program”

The model delivers results consistent with standard theory. Population fecundity and mortality trends with age Williams’ Hypothesis The evolution of semelparity and iteroparity A natural extension of the Euler-Lotka equation Differential survival of individuals removed from extrinsic death hazards

AGENDA The Model Reznick Results Non-senescence

The model also helps explain the Reznick results. Guppies from high predation environments show longer lifespan than low predation guppies (in apparent violation of Williams’ Hypothesis:

The model also helps explain the Reznick results (continued). Guppies from high predation environments also exhibit higher fecundity than low predation guppies:

The model can explain the increased lifespan. The “predator pruning hypothesis” of Abrams-Williams-Day: Different genotypes have different intrinsic lifespan Predators select individuals nearing the end of their intrinsic lifespan These individuals show deteriorating escape performance Genotypes with longer intrinsic lifespan therefore have a selective advantage Under predation, the intrinsic lifespan of the population increases But this is not essentially inconsistent with Williams’ Hypothesis

However, it may not explain the increased fecundity rate. The model takes the different fecundity rates for the High-predation vs. Low-predation populations as a given input. Current analysis is attempting to see if the model can be predictive of fecundity rates. Reznick claims that the High-predation populations are “better at everything”—higher fecundity, longer intrinsic lifespan, and better predator avoidance. It is as if they have an inherently greater metabolic budget to work with. This is a great puzzle.

AGENDA The Model Reznick Results Non-senescence

Under certain conditions, standard theory predicts non-senescent genotypes will dominate senescent ones.