title: Population divergence in the ontogenetic trajectories of foliar terpenes of a Eucalyptus species.
abstract: OBJECTIVE
  The development of plant secondary metabolites during early life stages can have significant ecological and evolutionary implications for plant-herbivore interactions. Foliar terpenes influence a broad range of ecological interactions, including plant defence, and their expression may be influenced by ontogenetic and genetic factors. This study investigates the role of these factors in the expression of foliar terpene compounds in Eucalyptus globulus seedlings.
  
  
  METHODS
  Seedlings were sourced from ten families each from three genetically distinct populations, representing relatively high and low chemical resistance to mammalian herbivory. Cotyledon-stage seedlings and consecutive leaf pairs of true leaves were harvested separately across an 8-month period, and analysed for eight monoterpene compounds and six sesquiterpene compounds.
  
  
  RESULTS
  Foliar terpenes showed a series of dynamic changes with ontogenetic trajectories differing between populations and families, as well as between and within the two major terpene classes. Sesquiterpenes changed rapidly through ontogeny and expressed opposing trajectories between compounds, but showed consistency in pattern between populations. Conversely, changed expression in monoterpene trajectories was population- and compound-specific.
  
  
  CONCLUSIONS
  The results suggest that adaptive opportunities exist for changing levels of terpene content through ontogeny, and evolution may exploit the ontogenetic patterns of change in these compounds to create a diverse ontogenetic chemical mosaic with which to defend the plant. It is hypothesized that the observed genetically based patterns in terpene ontogenetic trajectories reflect multiple changes in the regulation of genes throughout different terpene biosynthetic pathways.
authors.affiliation: School of Biological Sciences and National Centre for Future Forest Industries, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia and Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania, 7001, Australia cborzak@utas.edu.au.
authors.forename: Christina L
authors.initials: CL
authors.lastname: Borzak
authors.affiliation: School of Biological Sciences and National Centre for Future Forest Industries, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia and Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania, 7001, Australia.
authors.forename: Brad M
authors.initials: BM
authors.lastname: Potts
authors.affiliation: School of Biological Sciences and National Centre for Future Forest Industries, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia and Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania, 7001, Australia.
authors.forename: Noel W
authors.initials: NW
authors.lastname: Davies
authors.affiliation: School of Biological Sciences and National Centre for Future Forest Industries, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia and Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania, 7001, Australia.
authors.forename: Julianne M
authors.initials: JM
authors.lastname: O'Reilly-Wapstra
mesh_terms: D005052:Eucalyptus / Q000235:genetics* / Q000378:metabolism; D039821:Monoterpenes / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D036226:Seedlings / Q000235:genetics* / Q000378:metabolism; D012717:Sesquiterpenes / Q000378:metabolism; D013729:Terpenes / Q000378:metabolism*
chemical_list: D039821:Monoterpenes; D012717:Sesquiterpenes; D013729:Terpenes
keywords: Chemical defence; Eucalyptus globulus; foliar terpenes; genetic variation; herbivory; monoterpene; ontogenetic trajectory; plant ontogeny; population divergence; secondary metabolite; seedlings; sesquiterpene