title: Relative embryo length as an adaptation to habitat and life cycle in Apiaceae.
abstract: • The factors driving the evolution of the relative embryo length in Apiaceae were examined. We tested the hypothesis that seeds with large relative embryo length, because of more rapid germination, are beneficial in dry and open habitats and for short-lived species. We also analyzed to what extent delayed germination as a result of embryo growth can be considered a dormancy mechanism. • Hypotheses were tested by correlating the relative embryo length with other plant traits, habitat and climatic variables. The adaptive nature of the relative embryo length was determined by comparing the performance of a pure drift, Brownian motion (BM) model of trait evolution with that of a selection-inertia, Ornstein-Uhlenbeck (OU) model. • A positive correlation of the relative embryo length with germination speed and negative correlations with the amount of habitat shade, longevity and precipitation were found. An OU model, in which the evolution of longer embryos corresponded to a transition to habitats of high light, or to a short life cycle, outperformed significantly a BM model. • The results indicated that the relative embryo length may have evolved as an adaptation to habitat and life cycle, whereas dormancy was mainly related to temperature at the sampling sites.
authors.affiliation: Plant Ecology, Philipps-Universität Marburg, Karl-von-Frisch-Strasse 8, D-35043 Marburg, Germany.
authors.forename: Filip
authors.initials: F
authors.lastname: Vandelook
authors.affiliation: Laboratory of Plant Systematics, Institute of Botany and Microbiology, KU Leuven, PO Box 2437, BE-3001 Leuven, Belgium.
authors.forename: Steven B
authors.initials: SB
authors.lastname: Janssens
authors.affiliation: Seed Conservation Department, Royal Botanic Gardens Kew, Wakehurst Place, Ardingly, West Sussex RH17 6TN, UK.
authors.forename: Robin J
authors.initials: RJ
authors.lastname: Probert
mesh_terms: D000222:Adaptation, Physiological; D019661:Apiaceae / Q000254:growth & development* / Q000502:physiology*; D002980:Climate; D017753:Ecosystem; D018525:Germination / Q000502:physiology; D016018:Least-Squares Analysis; D016013:Likelihood Functions; D010802:Phylogeny; D019655:Quantitative Trait, Heritable; D012044:Regression Analysis; D012639:Seeds / Q000033:anatomy & histology* / Q000502:physiology*