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  • Evidence for adaptive radiation from a phylogenetic study of plant defenses.

    Author(s) : Agrawal, A. A.Fishbein, M.Halitschke, R.Hastings, A. P.Rabosky, D. L.Rasmann, S.

    Author Affiliation : Department of Ecology and Evolutionary Biology, Cornell University, Corson Hall, Ithaca, NY 14853-2701, USA.

    Author Email : agrawal@cornell.edu

    Journal article : Proceedings of the National Academy of Sciences of the United States of America 2009 Vol.106 No.43 pp.18067-18072 ref.46

    Abstract : One signature of adaptive radiation is a high level of trait change early during the diversification process and a plateau toward the end of the radiation. Although the study of the tempo of evolutionevolutionSubject Category: Natural Processes
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    has historically been the domain of paleontologists, recently developed phylogenetic tools allow for the rigorous examination of trait evolution in a tremendous diversity of organisms. Enemy-driven adaptive radiation was a key prediction of Ehrlich and Raven's coevolutionary hypothesis [Ehrlich PR, Raven PH (1964) Evolution 18:586-608], yet has remained largely untested. Here we examine patterns of trait evolution in 51 North American milkweed species (AsclepiasasclepiasSubject Category: Organism Names
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    ), using maximum likelihood methods. We study 7 traits of the milkweeds, ranging from seed sizeseed sizeSubject Category: Properties
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    and foliar physiological traits to defense traits (cardenolidescardenolidesSubject Category: Chemicals and Chemical Groups
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    , latexlatexSubject Category: Commodities and Products
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    , and trichomestrichomesSubject Category: Anatomical and Morphological Structures
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    ) previously shown to impact herbivoresherbivoresSubject Category: Organism Groups
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    , including the monarch butterfly. We compare the fit of simple random-walk models of trait evolution to models that incorporate stabilizing selection (Ornstein-Ulenbeck process), as well as time-varying rates of trait evolution. Early bursts of trait evolution were implicated for 2 traits, while stabilizing selection was implicated for several others. We further modeled the relationship between trait change and species diversification while allowing rates of trait evolution to vary during the radiation. Species-rich lineages underwent a proportionately greater decline in latex and cardenolides relative to species-poor lineages, and the rate of trait change was most rapid early in the radiation. An interpretation of this result is that reduced investment in defensive traits accelerated diversification, and disproportionately so, early in the adaptive radiation of milkweeds.

    ISSN : 0027-8424

    DOI : 10.1073/pnas.0904862106

    Record Number : 20093328168

    Publisher : National Academy of Sciences

    Location of publication : Washington

    Country of publication : USA

    Language of text : English

    Indexing terms for this abstract:

    Organism descriptor(s) : arthropodsarthropodsSubject Category: Organism Names
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    , AsclepiasasclepiasSubject Category: Organism Names
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    , insectsinsectsSubject Category: Organism Names
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    Descriptor(s) : adaptationadaptationSubject Category: Natural Processes
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    , arthropod pestsarthropod pestsSubject Category: Organism Groups
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    , cardenolidescardenolidesSubject Category: Chemicals and Chemical Groups
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    , defence mechanismsdefence mechanismsSubject Category: Miscellaneous
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    , evolutionevolutionSubject Category: Natural Processes
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    , herbivoresherbivoresSubject Category: Organism Groups
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    , insect pestsinsect pestsSubject Category: Organism Groups
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    , latexlatexSubject Category: Commodities and Products
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    , leaf arealeaf areaSubject Category: Properties
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    , leavesleavesSubject Category: Anatomical and Morphological Structures
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    , pestspestsSubject Category: Organism Groups
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    , phylogeneticsphylogeneticsSubject Category: Disciplines, Occupations and Industries
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    , plant pestsplant pestsSubject Category: Organism Groups
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    , seed sizeseed sizeSubject Category: Properties
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    , species diversityspecies diversitySubject Category: Properties
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    , species richnessspecies richnessSubject Category: Properties
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    , trichomestrichomesSubject Category: Anatomical and Morphological Structures
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    , water contentwater contentSubject Category: Properties
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    Identifier(s) : defense mechanismsdefense mechanismsSubject Category: Miscellaneous
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    , pest arthropods, pest insects

    Broader term(s) : AsclepiadaceaeasclepiadaceaeSubject Category: Organism Names
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    , GentianalesgentianalesSubject Category: Organism Names
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    , eudicotseudicotsSubject Category: Organism Names
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    , angiospermsangiospermsSubject Category: Organism Names
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    , SpermatophytaspermatophytaSubject Category: Organism Names
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    , plantsplantsSubject Category: Organism Names
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    , eukaryoteseukaryotesSubject Category: Organism Names
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    , HexapodahexapodaSubject Category: Organism Names
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    , arthropodsarthropodsSubject Category: Organism Names
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    , invertebratesinvertebratesSubject Category: Organism Names
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    , animalsanimalsSubject Category: Organism Names
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