Evolution of natal dispersal in spatially heterogenous environments

TL;DR

This paper investigates how natal dispersal strategies evolve in spatially heterogeneous environments, showing that evolution favors strategies leading to ideal-free distributions, especially when some patches cannot sustain populations.

Contribution

The study develops new mathematical methods to analyze natal dispersal evolution in continuous and discrete-time models, revealing conditions favoring ideal-free distributions over source-sink structures.

Findings

Dispersal strategies leading to ideal-free distributions displace source-sink strategies.

Sedentary populations can achieve ideal-free distributions in unsustainable patches.

Evolution favors natal dispersal strategies that optimize spatial distribution in stable environments.

Abstract

Understanding the evolution of dispersal is an important issue in evolutionary ecology. For continuous time models in which individuals disperse throughout their lifetime, it has been shown that a balanced dispersal strategy, which results in an ideal free distribution, is evolutionary stable in spatially varying but temporally constant environments. Many species, however, primarily disperse prior to reproduction (natal dispersal) and less commonly between reproductive events (breeding dispersal). As demographic and dispersal terms combine in a multiplicative way for models of natal dispersal, rather than the additive way for the previously studied models, we develop new mathematical methods to study the evolution of natal dispersal for continuous-time and discrete-time models. A fundamental ecological dichotomy is identified for the non-trivial equilibrium of these models: (i) the per-capita growth rates for individuals in all patches is equal to zero, or (ii) individuals in some patches experience negative per-capita growth rates, while individuals in other patches experience positive per-capita growth rates. The first possibility corresponds to an ideal-free distribution, while the second possibility corresponds to a "source-sink" spatial structure. We prove that populations with a dispersal strategy leading to an ideal-free distribution displace populations with dispersal strategy leading to a source-sink spatial structure. When there are patches which can not sustain a population, ideal-free strategies can be achieved by sedentary populations, and we show that these populations can displace populations with any irreducible dispersal strategy. Collectively, these results support that evolution selects for natal or breeding dispersal strategies which lead to ideal-free distributions in spatially heterogenous, but temporally homogenous, environments.