title: Global biogeography of seed dormancy is determined by seasonality and seed size: a case study in the legumes.
abstract: Seed dormancy is expected to provide ecological advantages by adjusting germination to the favorable growth period. However, many species produce nondormant seeds, particularly in wet tropical forests, a biogeographic pattern that is not well accounted for in current models. We hypothesized that the global distribution of dormant seeds derives from their adaptive value in predictably fluctuating (i.e. seasonal) environments. However, the advantage conferred by dormancy might ultimately depend on other seed attributes, particularly size. This general model was tested within a phylogenetically informed framework using a data set comprising > 216 000 world-wide observations of Fabaceae, spanning three orders of magnitude in seed size and including both dormant and nondormant seeds. Our results confirmed our hypothesis: nondormant seeds can only evolve in climates with long growing seasons and/or in lineages that produce larger seeds. Conversely, dormancy should be evolutionarily stable in temperate lineages with small seeds. When the favorable season is fleeting, seed dormancy is the only adaptive strategy. Based on these results, we predict that, within a given lineage, taxa producing larger, nondormant seeds will necessarily predominate in aseasonal environments, while plants bearing small, dormant seeds will be dominant under short growing seasons.
authors.affiliation: Department of Ecology, Facultad de Ciencias, Universidad de Granada, Avda. de la Fuentenueva s/n, Granada, 18071, Spain.|Estación Experimental de Zonas Áridas, EEZA-CSIC, Carretera de Sacramento s/n, La Cañada de San Urbano, 04120, Spain.|UMR 5175 CEFE - Centre d'Ecologie Fonctionnelle et Evolutive (CNRS), 1919 Route de Mende, Montpellier Cedex 05, F-34293, France.
authors.forename: Rafael
authors.initials: R
authors.lastname: Rubio de Casas
authors.affiliation: Harvard University Herbaria, 22 Divinity Ave., Cambridge, MA, 02138, USA.
authors.forename: Charles G
authors.initials: CG
authors.lastname: Willis
authors.affiliation: Department of Biology, McGill University, Stewart Biology Building, 1205 Ave. Docteur Penfield, Montreal, QC, Canada, H3A 1B1.|Département des Sciences Biologiques, Université du Québec à Montréal, Succursale Centre-ville, Montréal, QC, Canada, H3C 3P8.|Department of Ecology, Evolution & Behavior, University of Minnesota, 1479 Gortner Ave, Saint Paul, MN, 55108, USA.|Department of Biology & Ecology Center, Utah State University, Logan, UT, 84322, USA.
authors.forename: William D
authors.initials: WD
authors.lastname: Pearse
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY, 40506, USA.|Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, 40546, USA.
authors.forename: Carol C
authors.initials: CC
authors.lastname: Baskin
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY, 40506, USA.
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Baskin
authors.affiliation: Department of Ecology, Evolution & Behavior, University of Minnesota, 1479 Gortner Ave, Saint Paul, MN, 55108, USA.
authors.forename: Jeannine
authors.initials: J
authors.lastname: Cavender-Bares
mesh_terms: D005075:Biological Evolution; D007887:Fabaceae / Q000502:physiology*; D018525:Germination; D058974:Phylogeography; D057445:Plant Dormancy / Q000502:physiology*; D012621:Seasons; D012639:Seeds / Q000033:anatomy & histology / Q000502:physiology*
keywords: discrete traits; mixed models; phylogenetic comparative methods; physical dormancy; seed bank; seed germination; seed predation