Towards food web engineering. A study of genetic variability and experimental evolution with the predatory mite Amblyseius swirskii.

Resumo

This thesis is part of the project titled "Towards food web engineering: linking trait variability to ecosystem functioning" which has food web engineering (FWE) as its central point. FWE is an extension of biological pest control (BPC) that integrates ecology and evolution into crop management by combining experimental data with individual-based models (IBM). Therefore, the main objective is to generate experimental data that will feed, in the future, an IBM (Weaver). To this aim, this thesis covers the evaluation of genetic studies of traits relevant to BPC. To explore this, the model species was predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae), widely used as a biological control agent against some of the most important and damaging groups of pests in protected crops. Specifically, the genetic variability and genetic correlations of several traits from two populations, one commercial and one wild, were evaluated. Furthermore, the hypothesis that commercial populations should have less genetic variability than wild populations due to the appearance of undesirable effects during mass breeding processes was confirmed. Subsequently, an experimental evolution experiment was carried out, where subpopulations of this species were exposed to two selection pressures, one abiotic (high temperature) and another biotic (presence of a top-predator), for several generations, in a full-cross experimental design that allowed to disentangle evolutionary responses driven by either, or both selection forces. It was also evaluated whether there was any adaptation or evolutionary cost to said exposure. The most remarkable result was an evolution towards smaller sizes only in the presence of both stressors. Also, individuals from populations long-term exposed to high temperatures increased their developmental time. Results also showed no evidence of adaptation in any of the traits assessed. However, a cost associated to the evolutionary response was found in the evolutionary lines exposed to high temperatures. The results obtained in this thesis provide valuable information about the genetics of a wide list of relevant traits for pest control, and the genetic correlations between them. It also shows that populations under hostile environments undergo evolutionary processes that can jeopardize the success of biological pest control in the future. Furthermore, the data obtained in this thesis will be used to parameterize biological control systems using next generation individual-based models that incorporate genetic variability in traits to study emergent patterns of the dynamics of these agricultural systems, when exposed to hostile environments.