title: Biotic and abiotic factors associated with altitudinal variation in plant traits and herbivory in a dominant oak species.
abstract: OBJECTIVE
  It is generally thought that herbivore pressure is higher at lower elevations where climate is warmer and less seasonal, and that this has led to higher levels of plant defense investment at low elevations. However, the generality of this expectation has been called into question by recent studies.
  
  
  METHODS
  We tested for altitudinal gradients in insect leaf damage, plant defenses (phenolic compounds), and nutritional traits (phosphorus and nitrogen) in leaves of the long-lived tree Quercus robur, and further investigated the abiotic factors associated with such gradients. We sampled 20 populations of Q. robur distributed along an altitudinal gradient spanning 35-869 m above sea level, which covered most of the altitudinal range of this species and varied substantially in abiotic conditions, plant traits, and herbivory.
  
  
  RESULTS
  Univariate regressions showed that leaf herbivory, phenolics, and phosphorus increased toward higher elevations, whereas leaf nitrogen did not vary with altitude. Multiple regression analyses indicated that temperature was the single most important factor associated with herbivory and appears to be strongly associated with altitudinal variation in damage. Leaf phenolics were also correlated with herbivory, but in a manner that suggests these chemical defenses do not underlie altitudinal variation in damage. In addition, we found that variation in leaf traits (phenolics and nutrients) was in turn associated with both climatic and soil variables.
  
  
  CONCLUSIONS
  Overall, these findings suggest that altitudinal gradients in herbivory and defenses in Q. robur are uncoupled and that elevational variation in herbivory and plant traits responds mainly to abiotic factors.
authors.affiliation: Departamento de Ecología Tropical, Campus de Ciencias Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Apartado Postal 4-116, Itzimná. 97000. Mérida, Yucatán, México.
authors.forename: Luis
authors.initials: L
authors.lastname: Abdala-Roberts
authors.affiliation: Institute of Biology, Laboratory of Functional Ecology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland.
authors.forename: Sergio
authors.initials: S
authors.lastname: Rasmann
authors.affiliation: Department of Plant Sciences, University of California-Davis, One Shields Avenue, Davis, California, USA 95616.
authors.forename: Jorge C
authors.initials: JC
authors.lastname: Berny-Mier Y Terán
authors.affiliation: Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Carretera de Utrera km. 1 41013 Sevilla, Spain.
authors.forename: Felisa
authors.initials: F
authors.lastname: Covelo
authors.affiliation: Neuchâtel Platform of Analytical Chemistry, University of Neuchâtel, Rue Emile Argand 11, 2000 Neuchâtel, Switzerland.
authors.forename: Gaétan
authors.initials: G
authors.lastname: Glauser
authors.affiliation: Misión Biológica de Galicia (MBG-CSIC), Apdo. 28 36080 Pontevedra, Galicia, Spain xmoreira1@gmail.com.
authors.forename: Xoaquín
authors.initials: X
authors.lastname: Moreira
mesh_terms: D000531:Altitude; D000818:Animals; D060434:Herbivory; D007313:Insecta; D009584:Nitrogen / Q000378:metabolism; D010641:Phenotype; D010758:Phosphorus / Q000378:metabolism; D057865:Plant Immunity; D018515:Plant Leaves / Q000502:physiology; D029963:Quercus / Q000502:physiology*; D012044:Regression Analysis; D013312:Stress, Physiological; D014197:Trees
chemical_list: D010758:Phosphorus; D009584:Nitrogen
keywords: Spain; altitudinal gradient; climate; herbivory; phenolics; plant traits; soil variables