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Scale-dependent adaptive evolution and morphological convergence to climatic niche in Californian eriogonoids (Polygonaceae)

Authors

  • Anna Kostikova,

    1. Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
    2. Swiss Institute of Bioinformatics, Lausanne, Swizterland
    3. Landscape Dynamics, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
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  • Glenn Litsios,

    1. Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
    2. Swiss Institute of Bioinformatics, Lausanne, Swizterland
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  • Sarah Burgy,

    1. Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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  • Laura Milani,

    1. Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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  • Peter B. Pearman,

    1. Landscape Dynamics, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
    2. Department of Plant Biology and Ecology, University of the Basque Country UPV/EHU, Bilbao, Spain
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    • Both last authors led this study and supervised A.K.
  • Nicolas Salamin

    Corresponding author
    1. Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
    2. Swiss Institute of Bioinformatics, Lausanne, Swizterland
    • Correspondence: Nicolas Salamin, Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland.

      E-mail: nicolas.salamin@unil.ch

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    • Both last authors led this study and supervised A.K.

Abstract

Aim

Macroevolutionary patterns and processes change substantially depending on levels of taxonomic and ecological organization, and the resolution of environmental and spatial variability. In comparative methods, the resolution of environmental and spatial variability often defines the number of selective regimes used to test whether phenotypic characteristics are adaptively correlated with the environment. Here, we examine how investigator choice of the number of selective regimes, determined by varying the resolution of among-species variability in the species climatic niche (hereafter called ‘ecological scale’), influences trait morphological diversification among Eriogonoideae species. We assess whether adaptive or neutral processes drive the evolution of several morphological traits in these species.

Location

South-western North America.

Methods

We applied a phylogenetic framework of three evolutionary models to four morphological traits and the climatic niches of Eriogonoideae (in the buckwheat family, Polygonaceae). We tested whether morphological traits evolve in relation to climate by adaptive or neutral process, and whether the resulting patterns of morphological variability are conserved or convergent across the clade. We inspected adaptive models of evolution under different levels of resolution of among-species variability of the climatic niche.

Results

We show that morphological traits and climate niches of Eriogonoideae species are not phylogenetically conserved. Further, adaptive evolution of phenotypic traits is specific to climatic niche occupancy across this clade. Finally, the likely evolutionary process and the level of detectable niche conservatism change depending on the resolution of environmental variability of the climatic niche.

Main conclusions

Our study demonstrates the need to consider both the resolution of environmental variability and alternative evolutionary models to understand the morphological diversification that accompanies divergent adaptive evolution of lineages to climatic conditions.

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