Journal of evolutionary biology | 29 Sep 2015
E Garrido, LP Llamas-Guzmán and J Fornoni
Negative frequency-dependent selection (FDS), where rare genotypes are favoured by selection, is commonly invoked as a mechanism explaining the maintenance of genetic variation in plant defences. However, empirical tests of FDS in plant-herbivore interactions are lacking. We evaluated if the oviposition preference of the specialist herbivore Lema daturaphila is a mechanism through which this herbivore can exert FDS on its host plant Datura stramonium. The frequency of contrasting resistance-tolerance strategies was manipulated within experimental plots, and the plants were exposed to a similar initial density of their natural herbivore. Herbivore oviposition preference and final density, as well as plant damage and seed production were estimated. Overall, we found that the high resistant-low tolerant genotypes produced four times more seeds when common than when rare, while the high tolerant-low resistant genotypes achieved twice its fitness when rare than when common. This pattern was the result of differential oviposition preferences. In addition, when the high resistant-low tolerant genotypes were common there was a three-fold decreased in herbivore final density which led to a decrease in damage level by 10%. Thus, in our experiment positive frequency-dependent selection seem to favour resistance over tolerance. We discuss how this results would change if the extent of herbivore local adaptation and damage modify the pattern of positive frequency-dependent selection acting on resistance and the optimal allocation to tolerance. This article is protected by copyright. All rights reserved.
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