title: A Ni hyperaccumulator and a congeneric non-accumulator reveal equally effective defenses against herbivory.
abstract: The defense hypothesis is commonly used to explain the adaptive role of metal hyperaccumulation. We tested this hypothesis using two Brassicaceae congeneric species: Alyssum pintodasilvae, a Ni hyperaccumulator, and the non-accumulator Alyssum simplex both growing on serpentine soils in Portugal. Artificial diet disks amended with powdered leaves from each plant species were used to compare the performance (mortality, biomass change) and feeding behavior of Tribolium castaneum in no-choice and choice tests. The performance of T. castaneum was not affected at several concentrations of A. pintodasilvae or A. simplex in no-choice tests. However, the consumption of plant-amended disks was significantly lower than that of control disks, irrespectively of the species fed. Accordingly, when insects were given an alternative food choice, disks of both plant species were significantly less consumed than control disks. Moreover, insects did not discriminate between disks in the combination "A. pintodasilvae+A. simplex". Contrary to our expectations, these results suggest that both plant species have equally effective defenses against herbivory. While Ni is believed to be part of the deterrence mechanism in the hyperaccumulator A. pintodasilvae, it seems likely that organic compounds, possibly glucosinolates, play an important role in the defense of A. simplex or in both species.
authors.affiliation: Instituto Superior de Agronomia, Departamento dos Recursos Naturais, Ambiente e Território, Tapada da Ajuda, 1349-017 Lisboa, Portugal; Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, PO Box 3046, 3001-401 Coimbra, Portugal. Electronic address: liliana.vboas@gmail.com.
authors.forename: Liliana
authors.initials: L
authors.lastname: Vilas Boas
authors.forename: Susana C
authors.initials: SC
authors.lastname: Gonçalves
authors.forename: António
authors.initials: A
authors.lastname: Portugal
authors.forename: Helena
authors.initials: H
authors.lastname: Freitas
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Gonçalves
mesh_terms: D000818:Animals; D018533:Biomass; D019607:Brassicaceae / Q000378:metabolism*; D005247:Feeding Behavior / Q000187:drug effects; D020387:Food Chain; D060434:Herbivory / Q000187:drug effects*; D008136:Longevity / Q000187:drug effects; D009532:Nickel / Q000378:metabolism* / Q000633:toxicity*; D011174:Portugal; D013045:Species Specificity; D014231:Tribolium / Q000187:drug effects* / Q000469:parasitology
chemical_list: D009532:Nickel
keywords: Alyssum pintodasilvae; Alyssum simplex; Inorganic defense hypothesis; Ni hyperaccumulation; Serpentine soil; Tribolium castaneum