Abstracts (first author)
Experimental adaptation of the phytophagous spider mite, Tetranychus urticae to a new host plant
Our ultimate goal is to identify the underlying genetic mechanisms of adaptation of phytophagous mites, Tetranychus urticae, to tomato plants, i.e. a new host species. For this purpose, we transferred in replicate lines on tomato plants individuals from two experimental groups consisting of independent ancestral populations previously maintained for four hundred generations on cucumber and bean plants. For each of the four (two ancestral and two evolved) treatments we measured on tomato leaves individual changes in life-history traits after 25 generations and then calculated growth rates from female individual measures; an additional one-generation transfer on tomato leaves before measures allowed control of potential genotype × environment effects. After 25 generations, growth rate of individuals originating from the cucumber ancestral populations was identical between the replicate lines maintained on cucumber and those transferred on tomato plants, despite the male adult survival being higher for the latter. In contrast, growth rate was higher for individuals transferred on tomato than those maintained on bean plants, mainly due to an increase in female fecundity and a decrease in the development time of both male and female individuals transferred on tomato plants. We are now comparing these data obtained on tomato leaves to similar data measured on entire tomato plants so as to evaluate potential differences in induced-defenses between leaves and plants, and subsequent potential differences in adaptation measures.