The ecological causes and consequences of hard and soft selection

Donovan A. Bell, Ryan P. Kovach, Zachary L. Robinson, Andrew R. Whiteley, Thomas E. Reed

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Interactions between natural selection and population dynamics are central to both evolutionary-ecology and biological responses to anthropogenic change. Natural selection is often thought to incur a demographic cost that, at least temporarily, reduces population growth. However, hard and soft selection clarify that the influence of natural selection on population dynamics depends on ecological context. Under hard selection, an individual's fitness is independent of the population's phenotypic composition, and substantial population declines can occur when phenotypes are mismatched with the environment. In contrast, under soft selection, an individual's fitness is influenced by its phenotype relative to other interacting conspecifics. Soft selection generally influences which, but not how many, individuals survive and reproduce, resulting in little effect on population growth. Despite these important differences, the distinction between hard and soft selection is rarely considered in ecology. Here, we review and synthesize literature on hard and soft selection, explore their ecological causes and implications and highlight their conservation relevance to climate change, inbreeding depression, outbreeding depression and harvest. Overall, these concepts emphasise that natural selection and evolution may often have negligible or counterintuitive effects on population growth—underappreciated outcomes that have major implications in a rapidly changing world.

    Original languageEnglish
    Pages (from-to)1505-1521
    Number of pages17
    JournalEcology Letters
    Volume24
    Issue number7
    DOIs
    StatePublished - Jul 2021

    Keywords

    • eco-evolutionary dynamics
    • evolutionary rescue
    • global change
    • hard selection
    • inbreeding depression
    • natural selection
    • outbreeding depression
    • population dynamics
    • sexual selection
    • soft selection

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