Carl Boettiger | Search bioRxiv

bioRxiv2016

Measurement uncertainty matters: ecological management using POMDPs

Over the past 30 years, researchers have used various approximations to address the impact of measurement uncertainty on optimal management policy.This literature has consistently suggested the counter-intuitive proposition that increasing harvest levels in the presence of measurement error is often optimal. Here, we use state-of-the art algorithms for Partially Observed Markov Decision Processes (POMDPs) to provide the first complete solution to this classic problem, and demonstrate that contrary to previous work, the resulting policy is usually more conservative than without measurement error. We demonstrate that management which underestimates the measurement error results in both low economic returns and high frequency of stock collapses, while overestimating the role of measurement error can still result in nearly-optimal economic performance while avoiding stock collapse.

Ecology↗

bioRxiv2015

After the games are over: life-history trade-offs drive dispersal attenuation following range expansion

Increased dispersal propensity often evolves on expanding range edges due to the Olympic Village effect, which involves the fastest and fittest finding themselves together in the same place at the same time, mating, and giving rise to like individuals. But what happens after the ranges leading edge has passed and the games are over? Although empirical studies indicate that dispersal propensity attenuates following range expansion, hypotheses about the mechanisms driving this attenuation have not been clearly articulated or tested. Here we use a simple model of the spatiotemporal dynamics of two phenotypes, one fast and the other slow, to propose that dispersal attenuation beyond pre-expansion levels is only possible in the presence of trade-offs between dispersal and life-history traits. The Olympic Village effect ensures that fast dispersers pre-empt locations far from the ranges previous limits. When trade-offs are absent, this pre-emptive spatial advantage has a lasting impact, with highly dispersive individuals attaining equilibrium frequencies that are strictly higher than their introduction frequencies. When trade-offs are present, dispersal propensity decays rapidly at all locations. Our models results about the post-colonization trajectory of dispersal evolution are clear and, in principle, should be observable in field studies. We conclude that empirical observations of post-colonization dispersal attenuation offer a novel way to detect the existence of otherwise elusive trade-offs between dispersal and life-history traits.

Ecology↗