In plant leaves, resource use follows a trade-off between rapid resource capture and conservative storage. This "worldwide leaf economics spectrum" consists of a suite of intercorrelated leaf traits, among which leaf mass per area, LMA, is one of the most fundamental as it indicates the cost of leaf construction and light-interception borne by plants. We conducted a broad-scale analysis of the evolutionary history of LMA across a large dataset of 5401 vascular plant species. The phylogenetic signal in LMA displayed low but significant conservatism, that is, leaf economics tended to be more similar among close relatives than expected by chance alone. Models of trait evolution indicated that LMA evolved under weak stabilizing selection. Moreover, results suggest that different optimal phenotypes evolved among large clades within which extremes tended to be selected against. Conservatism in LMA was strongly related to growth form, as were selection intensity and phenotypic evolutionary rates: woody plants showed higher conservatism in relation to stronger stabilizing selection and lower evolutionary rates compared to herbaceous taxa. The evolutionary history of LMA thus paints different evolutionary trajectories of vascular plant species across clades, revealing the coordination of leaf trait evolution with growth forms in response to varying selection regimes.

Centre for Functional Ecology University of Coimbra Coimbra Portugal

Centro Flora Autoctona c o Consorzio Parco Monte Barro via Bertarelli 11 1 23851 Galbiate Italy

CNRS Centre d'Écologie Fonctionnelle et Évolutive UMR 5175 1919 route de Mende 34293 Montpellier Cedex 5 France

CNRS Centre d'Écologie Fonctionnelle et Évolutive UMR 5175 1919 route de Mende 34293 Montpellier Cedex 5 France ; UMR PVMBT Université de la Réunion CIRAD 7 chemin de l'IRAT 94710 Saint Pierre France

Community and Conservation Ecology Group PO Box 14 9750 AA Haren The Netherlands

DBSF Università degli Studi dell'Insubria Via J H Dunant 3 1 21100 Varese Italy

Department of Archaeology The University Sheffield S1 4ET UK

Department of Biological Sciences Macquarie University New South Wales 2109 Australia

Department of Biology University of Wisconsin Eau Claire Phillips Hall 353 Eau Claire Wisconsin 4702 4004

Department of Botany Stockholm University Stockholm 106 91 Sweden

Department of Forest Resources and Institute on the Environment University of Minnesota St Paul Minnesota ; Hawkesbury Institute for the Environment University of Western Sydney Hawkesbury New South Wales Australia

Department of Molecular Biology and Ecology of Plants Faculty of Life Sciences Tel Aviv University Tel Aviv 69978 Israel

Department of Plant Production University of Milan via Celoria 2 1 20133 Milan Italy

INRA UMR 1248 AGIR Equipe ORPHEE BP 52627 Auzeville 31326 Castanet Tolosan France

Institute of Botany Academy of Sciences of the Czech Republic Dukelská 135 CZ 37982 Třeboň Czech Republic

Instituto Multidisciplinario de Biología Vegetal and FCEFyN Universidad Nacional de Córdoba Casilla de Correo 495 Vélez Sársfield 299 5000 Córdoba Argentina

James Hutton Institute Craigiebuckler Aberdeen AB15 8QH UK

Laboratoire d'Écologie Alpine Université Joseph Fourier BP 53 F 38042 Grenoble Cedex 09 France

Laboratory of Rangeland Ecology Aristotle University of Thessaloniki 54124 Thessaloniki Greece

Landscape Ecology Group Carl von Ossietzky University of Oldenburg P O Box 2503 26111 Oldenburg Germany

Landscape Ecology Group Carl von Ossietzky University of Oldenburg P O Box 2503 26111 Oldenburg Germany ; Landscape Ecology and Consulting Lerchenstrasse 20 26215 Wiefelstede Germany

Norwegian Institute for Nature Research Tungasletta 2 7485 Trondheim Norway

UR B and SEF CIRAD TA C 105 D Campus International de Baillarguet 34398 Montpellier Cedex 5 France

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