title: Importance of whole-plant biomass allocation and reproductive timing to habitat differentiation across the North American sunflowers.
abstract: Trait-based plant ecology attempts to use small numbers of functional traits to predict plant ecological strategies. However, a major gap exists between our understanding of organ-level ecophysiological traits and our understanding of whole-plant fitness and environmental adaptation. In this gap lie whole-plant organizational traits, including those that describe how plant biomass is allocated among organs and the timing of plant reproduction. This study explores the role of whole-plant organizational traits in adaptation to diverse environments in the context of life history, growth form and leaf economic strategy in a well-studied herbaceous system.
  
  
  
  A phylogenetic comparative approach was used in conjunction with common garden phenotyping to assess the evolution of biomass allocation and reproductive timing across 83 populations of 27 species of the diverse genus Helianthus (the sunflowers).
  
  
  
  Broad diversity exists among species in both relative biomass allocation and reproductive timing. Early reproduction is strongly associated with resource-acquisitive leaf economic strategy, while biomass allocation is less integrated with either reproductive timing or leaf economics. Both biomass allocation and reproductive timing are strongly related to source site environmental characteristics, including length of the growing season, temperature, precipitation and soil fertility.
  
  
  
  Herbaceous taxa can adapt to diverse environments in many ways, including modulation of phenology, plant architecture and organ-level ecophysiology. Although leaf economic strategy captures one key aspect of plant physiology, on their own leaf traits are not particularly predictive of ecological strategies in Helianthus outside of the context of growth form, life history and whole-plant organization. These results highlight the importance of including data on whole-plant organization alongside organ-level ecophysiological traits when attempting to bridge the gap between functional traits and plant fitness and environmental adaptation.
authors.affiliation: University of Central Florida, Orlando, FL 32816, USA.|Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Chase M
authors.initials: CM
authors.lastname: Mason
authors.affiliation: Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.|Interdisciplinary Toxicology Program, University of Georgia, Athens, GA 30602, USA.|Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.
authors.forename: Eric W
authors.initials: EW
authors.lastname: Goolsby
authors.affiliation: University of Central Florida, Orlando, FL 32816, USA.|Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Kaleigh E
authors.initials: KE
authors.lastname: Davis
authors.affiliation: Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Devon V
authors.initials: DV
authors.lastname: Bullock
authors.affiliation: Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Donovan
mesh_terms: D018533:Biomass; D017753:Ecosystem; D006368:Helianthus / Q000235:genetics / Q000502:physiology*; D009656:North America; D010641:Phenotype; D010802:Phylogeny; D018515:Plant Leaves / Q000502:physiology; D012098:Reproduction
keywords: Biomass; Helianthus; bud; climate; daylength; flower; growing season; leaf; life history; root; soil fertility; stem