OVIPOSITION RESPONSE OF PIERIS RAPAE TO ENVIRONMENTALLY INDUCED VARIATION IN BRASSICA NIGRA

Abstract

Oviposition preferences of field collected Pieris rapae (L.) adults were tested on Brassica nigra (Koch) plants which had been grown under four nutrient treatments. Each oviposition trial tested the preference between two treatments. In some oviposition preference tests females demonstrated a clear preference for one treatment, but in other trials, no preferences were observed. Leaf water content was implicated as a phenotypic characteristic associated with oviposition preference. Demonstrated oviposition preferences were always accompanied by statistically different water contents of treatment plants. No oviposition preferences were observed when the water contents of the treatment plants were similar. RÉSUMÉ PONTE DE PIERIS RAPAE EN RÉPONSE A DES MODIFICATIONS INDUITES PAR L'ENVIRONNEMENT CHEZ BRASSICA NIGRA Des pieds de Brassica nigra se sont développés dans quartre situations nutritives différentes (solution nutritive de base: BNS, solution pauvre en soufre: low S; solution pauvre en azote: low N et solution nutritive de base abaissée: low BNS). Des femelles de Pieris rapae ont pu choisir leur lieu de ponte entre les plantes de ces différentes catégories. Un schéma de comparaison a été mis au pont en utilisant les pieds BNS comme témoins. Les femelles pondent de préférence sur les plantes BNS en compétition avec des plantes low N ou low BNS, mais ne font aucune différence entre BNS et plantes low S. Les teneurs en eau et en allylisothiocyanate (AITC) des feuilles isolées des plantes traitées ont été examinées. La teneur en AITC des plantes low S est plus faible que celle des plantes BNS; les plantes low N ont une teneur en AITC supérieure à celle des plantes BNS; il n'y a pas de différence significative dans la teneur en AITC des plantes BNS et low BNS. Les teneurs en eau des plantes BNS et low S sont semblables, tandis que les plantes BNS ont une teneur en eau supérieure à celles des plantes low N et low BNS. Une analyse des distributions des pontes entre les différents types de plantes, et des ceufs sur une plante, montre qu'elles sont liées à la teneur en eau des feuilles. Il n'y a pas de relation apparente entre la distribution des œufs et la concentration en AITC.

Plant Resistance to Insect Herbivores: A Field Test of the Environmental Stress Hypothesis

“…For example, Dentaria diphylla was heavily damaged by insects when transplanted from forest to old field (Hicks and Tahvanainan 1974). Brassica nigra grown in the laboratory with lower soil water availabilities was preferentially used by Pieris rapae (Wolfson 1980(Wolfson , 1982. And, in our study system, greater insect damage occurs on bittercress plants: ( (Louda 1986); and (4) on chemically stressed treatments (Louda 1988).…”

“…In contrast to the laboratory results (Wolfson 1982), oviposition and feeding by Pieris rapae were not greater on cabbages that were grown in pots at lower water availabilities (Miles et al 1982b, Myers 1985. The next obvious step, which we take here, is to experimentally evaluate both the response of the plant and of the insect herbivores to the imposition of moderate stress under natural field conditions.…”

“…We conclude that when nitrogen content is high and similar among co-occurring plants, as in this system, other differences such as sugar content will mediate herbivory by adapted insects and its impact on plant performance. Wolfson (1980Wolfson ( , 1982 found that oviposition and growth of Pieris rapae increased on Brassica nigra on plants with limited water.…”

Defence mechanisms of Brassicaceae: implications for plant-insect interactions and potential for integrated pest management. A review

“…In another study from the 1980s regarding oviposition preferences of field-collected P. rapae butterflies towards B. nigra plants, leaf water content was considered as a phenotypic characteristic associated with oviposition preference (Wolfson, 1980). Renwick and Radke (1985) further showed that oviposition by P. rapae on cabbage was deterred by homogenised cabbage tissue sprayed onto intact plants.…”

Patterns of Resource Use by a Drosophilid (Diptera) Leaf Miner on a Native Crucifer

“…Selective pressures should result in females ovipositing in leaves which promote increased larval development and survival (Mitchell 1975, Wiren & Larsson 1984, Larsson et al 1986; but see Chew 1977, Wolfson 1982. Therefore, larval occurrence and damage should reflect qualitative and quantitative differences in plant quality detectable by the ovipositing female (Chew 1977, Rausher 1979.…”