Herbivoria em Erechtites valerinaefolia DC. (Asteraceae) : distribuição de ataque dos herbivoros e respostas compensatorias da planta

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

The interactions between Erechtites valerianaefolia De. (Asteraceae) and their associated herbivores have been studied Irom July 1991 to May 1993 in Serra do Japi Jundiaí, SP, and Irom Ju1y 1992 to May 1993 in Fazenda Lageado, Botucatu, SP. The main objectives of this study were to test the hypothesis that account for the herbivores preference concerning the vigor of the host plants (The Vigorous Plant Hypothesis and The Stressed Plant Hypothesis) and the Compensatory Responses of the host plants (Undercompensatory, Equivalent and Overcompensatory Hypothesis). A single parcel in each locality was used for monitoring the organisms in order to describe the phenology, longevity and relationships between plants and their herbivores. Biometrical pararneters such as height, nwnber of branches, number of leaves, number of reproductive structures, foliar area and dry weight of the stem, leaves and reproductive structures were analysed to evaluate the size and reproductive effort of plants collected in early dispersion. E. valerianaefolia has a number of characteristics that favour the attack of adults and I.. endogenous larvas of Agatomerus signatus KIug, 1824 (Megalopodinae, Chrysomelidae) and of an non identified apical meristem forager. Both groups of herbivores share the resource, the first attacking exclusively reproducing plants and the other attacking I3exclusively plants on the vegetative stage. In the presence of the megalopodineous borers, the target tissues around the tunnel suffer a modification to become rich in starch grains. The attack probability is larger for the more vigorous plants, specially with regard to megalopodineous. The attacked plants replace the 10st tissues and can also increase their reproductive effort. These plants had been usually associated with sites that were more suitable to the growth, within the studied parcels, in both 10ca1ities. The data support The Vigorous Plant Hypothesis and the Compensatory Reactions Gradiente but reject the Undercompensation. Therefore, a fitness reduction due to herbivory in the E. va/erianaefo/ia populations was not found

ASSUNTO(S)

herbivoro plantas

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