title: Plant defence as a complex and changing phenotype throughout ontogeny.
abstract: OBJECTIVE
  Ontogenetic changes in anti-herbivore defences are common and result from variation in resource availability and herbivore damage throughout plant development. However, little is known about the simultaneous changes of multiple defences across the entire development of plants, and how such changes affect plant damage in the field. The aim of this study was to assess if changes in the major types of plant resistance and tolerance can explain natural herbivore damage throughout plant ontogeny.
  
  
  METHODS
  An assessment was made of how six defensive traits, including physical, chemical and biotic resistance, simultaneously change across the major transitions of plant development, from seedlings to reproductive stages of Turnera velutina growing in the greenhouse. In addition, an experiment was performed to assess how plant tolerance to artificial damage to leaves changed throughout ontogeny. Finally, leaf damage by herbivores was evaluated in a natural population.
  
  
  RESULTS
  The observed ontogenetic trajectories of all defences were significantly different, sometimes showing opposite directions of change. Whereas trichome density, leaf toughness, extrafloral nectary abundance and nectar production increased, hydrogen cyanide and compensatory responses decreased throughout plant development, from seedlings to reproductive plants. Only water content was higher at the intermediate juvenile ontogenetic stages. Surveys in a natural population over 3 years showed that herbivores consumed more tissue from juvenile plants than from younger seedlings or older reproductive plants. This is consistent with the fact that juvenile plants were the least defended stage.
  
  
  CONCLUSIONS
  The results suggest that defensive trajectories are a mixed result of predictions by the Optimal Defence Theory and the Growth-Differentiation Balance Hypothesis. The study emphasizes the importance of incorporating multiple defences and plant ontogeny into further studies for a more comprehensive understanding of plant defence evolution.
authors.affiliation: Instituto de Ecología, Universidad Nacional Autónoma de México, Apartado Postal 70-275, Ciudad Universitaria, CP 04510, Mexico DF, Mexico.
authors.forename: Sofía
authors.initials: S
authors.lastname: Ochoa-López
authors.affiliation: Instituto de Ecología, Universidad Nacional Autónoma de México, Apartado Postal 70-275, Ciudad Universitaria, CP 04510, Mexico DF, Mexico.
authors.forename: Nora
authors.initials: N
authors.lastname: Villamil
authors.affiliation: Instituto de Ecología, Universidad Nacional Autónoma de México, Apartado Postal 70-275, Ciudad Universitaria, CP 04510, Mexico DF, Mexico.
authors.forename: Paulina
authors.initials: P
authors.lastname: Zedillo-Avelleyra
authors.affiliation: Instituto de Ecología, Universidad Nacional Autónoma de México, Apartado Postal 70-275, Ciudad Universitaria, CP 04510, Mexico DF, Mexico kboege@unam.mx.
authors.forename: Karina
authors.initials: K
authors.lastname: Boege
mesh_terms: D000898:Antibiosis; D060434:Herbivory; D008800:Mexico; D010641:Phenotype; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D029647:Turnera / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
keywords: Compensatory growth; Passifloraceae; Turnera velutina; extrafloral nectaries; herbivory; ontogenetic trajectories; plant defence; plant–animal interaction; tolerance