Abstract
The evolution of the match between the phenotype of organisms and their environment is a major issue in evolutionary biology, especially in a context of global change. During my PhD, I investigated the adaptive response to spatio-temporal environmental heterogeneity at different geographic and temporal scales of the spotted wing drosophila Drosophila suzukii, an invasive generalist pest of fruit crops. I used ecological genetic approaches, that combine populations genomics and experimental approaches focusing on lifehistory trait analyses. Based on an association study between genome-wide allelic variations and the invasive or native status of 22 populations sampled worldwide, I identified candidate genes whose allelic variation was strongly associated with the invasion status of D. suzukii. On a finer time and geographic scale (i.e., within a region of the invaded area), I studied the adaptive response of this species to spatiotemporal heterogeneity in host fruit availability. Using experimental evolution in the lab, I found that local adaptation patterns to host fruits emergence within less than 30 generations. Surprisingly, I detected a similar pattern in natural populations that evolved for less than four generations on the same fruit in the field. The speed of adaptive responses observed in natura raises important questions regarding the nature and the dynamics of processes influencing the evolution of fine geographic scale local adaptation in spatiotemporally heterogeneous environments. This PhD work provides new conceptual and methodological elements that improve our understanding of the dynamics of the adaptation of phytophagous insects to their host plant and of the evolutionary changes occurring during the invasion process.