title: Solar UV-B radiation affects leaf quality and insect herbivory in the southern beech tree Nothofagus antarctica.
abstract: We examined the effects of solar ultraviolet-B (UV-B) radiation on plant-insect interactions in Tierra del Fuego (55 degrees S), Argentina, an area strongly affected by ozone depletion because of its proximity to Antarctica. Solar UV-B under Nothofagus antarctica branches was manipulated using a polyester plastic film to attenuate UV-B (uvb-) and an Aclar film to provide near-ambient UV-B (uvb+). The plastic films were placed on both north-facing (i.e., high solar radiation in the Southern Hemisphere) and south-facing branches. Insects consumed 40% less leaf area from north- than from south-facing branches, and at least 30% less area from uvb+ branches than from uvb- branches. The reduced herbivory on leaves from uvb+ branches occurred for both branch orientations. Leaf mass per area increased and relative water content decreased on north- versus south-facing branches, while no differences were apparent between the UV-B treatments. Solar UV-B did lead to lower gallic acid concentration and higher flavonoid aglycone concentration in uvb+ leaves relative to uvb- leaves. Both the flavonoid aglycone and quercetin-3-arabinopyranoside were higher on north-facing branches. In laboratory preference experiments, larvae of the dominant insect in the natural community, Geometridae "Brown" (Lepidoptera), consumed less area from field-grown uvb+ leaves than from uvb- leaves in 1996-97, but not in 1997-98. Correlation analyses suggested that the reduction in insect herbivory in the field under solar UV-B may be mediated in part by the UV-B effects on gallic acid and flavonoid aglycone.
authors.affiliation: IFEVA, Consejo Nacional de Investigaciones Científicas y Técnicas and Universidad de Buenos Aires, Av. San Martín 4453, C1417 DSE, Buenos Aires, Argentina.
authors.forename: M Cecilia
authors.initials: MC
authors.lastname: Rousseaux
authors.forename: Riitta
authors.initials: R
authors.lastname: Julkunen-Tiitto
authors.forename: Peter S
authors.initials: PS
authors.lastname: Searles
authors.forename: Ana L
authors.initials: AL
authors.lastname: Scopel
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Aphalo
authors.forename: Carlos L
authors.initials: CL
authors.lastname: Ballaré
mesh_terms: D000818:Animals; D000864:Antarctic Regions; D017753:Ecosystem; D007313:Insecta / Q000502:physiology*; D007814:Larva / Q000502:physiology; D018515:Plant Leaves / Q000737:chemistry / Q000528:radiation effects; D013472:Sunlight; D014197:Trees / Q000528:radiation effects*; D014466:Ultraviolet Rays