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RESEARCH PRODUCT

Intérêts du phénotypage de la personnalité pour améliorer la lutte biologique : cas d’étude chez l’auxiliaire Trichogramma evanescens

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description

One promising approach to improve the use of biological control agents (BCA) consists in the exploitation of intraspecific variation on traits related to mass-rearing or field performance. Consistent inter-individual variations in behaviour (known as personality) have never been considered in biological control (BC) while they have proved to be heritable and correlated to phenotypic traits possibly related to fitness in rearing or field conditions. The aim of this PhD thesis was (i) to develop an experimental design to measure personality traits in a the egg-parasitoid Trichogramma evanescens, and (ii) to evaluate the feasibility and interest of phenotyping personality traits to set and improve selection programmes in this BCA species: by estimating the broad-sense heritability of personality traits and investigate their relationships with traits related to fitness and biocontrol performance. First, we developed a videotracking design to measure behavioural traits and found, for the first time in this species, consistent individual differences in boldness, activity and exploration, measured on 1,049 individuals (on which we also measured fecundity, longevity and tibia length) from 24 isogenic lines of T. evanescens. Personality differences between the 24 isogenic lines suggested a genetic origin of the variations in activity and exploration (broad-sense heritability estimates from 0.06 to 0.11), and revealed a trade-off between exploration and fecundity. We then conducted field experiments in cornfields, over 38 released points, to measure field characteristics of these isogenic lines (number of egg patches parasitized, mean and maximum distance between release point and oviposition sites) and investigate the effect of personality traits on these field variables. Our results suggest that personality traits influence the mean distance between release point and oviposition sites while this not the case for three traits commonly considered in biocontrol programmes (fecundity, longevity and tibia length). To conclude, we studied for the first time the link between lab-measured personality traits and movement in the field and discussed about further studies and development needed to integrate personality in biological control agents’ selection programmes in order to improve their efficiency.