Plasmid macro-evolution: selection of deletions during adaptation in a nutrient-limited environment

A study was made of the intra-and inter-population variability of the main traits involved in Trichogramma (T. brassicae and T. cacoeciae) efficiency in host exploitation: longevity, fecundity, progeny viability, progeny sex ratio and progeny allocation. The analysis of isofemale strains shows that differences in progeny viability, progeny sex ratio and progeny allocation are transmissible and relatively stable over two successive generations. Comparison of three strains of T. brassicae originating from different locations, demonstrates differences in fecundity, progeny sex ratio and progeny allocation. Differences in host exploitation strategies also exist between two sympatric populations of T. brassicae and T. cacoeciae. No significant correlation appears between the traits which discriminate populations. The ecological and evolutionary significance and the agronomical importance of the results are discussed.