Ecology of Arabidopsis thaliana : local adaptation and interaction with herbivores

Abstract

As first step the impact of herbivory and abiotic factors on population dynamics of Arabidopsis thaliana were studied. Ceutorhynchus atomus and C. contractus were identified as the major insect herbivores on A. thaliana population, reducing seed production by more than 40%. Mortality from February to April was identified as a key- factor. Next, variation in morphological and life history trait and sutability of A. thaliana as food for weevils for A. thaliana population growing in the dune and inland habitat were studied. These variatioan were genetically and environmentally based. Plants at its home site had the highest fitness, which demonstrates adaptation to local environment. To examine the cause of differences in plant defense we compared herbivory on fruits with data on glucosinolate concentration of seeds, collected in the field. Fruit damage by adult weevils and their larvae was not correlated with field concentration of glucosinolates. We conclude that other factors might also be involved in defense against herbivory by the weevils. Finally, to test if glucosinolates evolve as a contrasting selection pressure by different herbivores we look if the generalist herbivore Spodoptera exigua and the specialist herbivores Plutella xylostella were differently affected by chemical compounds in the leaves. No significant correlations were found between larval weight of P. xylostella and glucosinolates in the leaves but glucosinolates negatively correlated with larval weight of S. exigua. We suggest that generalist herbivores may play a major role in this process.