Phenotypic and Transcriptomic Responses to Stress Differ According to Population Geography in an Invasive Species

Abstract

Adaptation to rapid environmental changes must occur within a short time scale. In this context, studies of invasive species may provide insights into the underlying mechanisms of rapid adaptation as these species have repeatedly encountered and adapted to novel environmental conditions. We investigated how invasive and non-invasive genotypes of Drosophila suzukii deal with oxidative stress at the phenotypic and molecular levels. We also studied the impact of transposable element (TE) insertions on the gene expression in response to stress. Our results show that flies from invasive areas (France and USA) live longer in natural conditions than the ones from native Japanese areas. As expected, lifespan for all genotypes was significantly reduced following exposure to paraquat, but this reduction varied among genotypes (genotype by environment interaction, GEI) with invasive genotypes appearing more affected by exposure than non-invasive ones. A transcriptomic analysis of genotypes upon paraquat treatment detected many genes differentially expressed (DE). While a small core set of genes were DE in all genotypes following paraquat exposure, much of the response of each genotype was unique. Moreover, we showed that TEs were not activated after oxidative stress and DE genes were significantly depleted of TEs. In conclusion, it's likely that transcriptomic changes are involved in the rapid adaptation to local environments. We provide new evidence that in the decade since the invasion from Asia, the sampled genotypes in Europe and USA of D. suzukii diverged from the ones from the native area regarding their phenotypic and genomic response to oxidative stress.

Transposable elements as evolutionary driving force to ecological speciation in cactophilicDrosophilaspecies

“…On the other hand, generalist species have more genetic variation and less structured populations, due to the large range of resources (123). A comparative analysis between generalist and specialist Drosophila species revealed that niche amplitude does not play a role in TE dynamics in the genomes (124). Nevertheless, several studies have proposed that the successful adaptation to new environments in invasive species might be associated with TEs activity, despite reduced genetic diversity caused by founder effects (125,126).…”

Diversification and recurrent adaptation of the synaptonemal complex inDrosophila

“…As the RNA-seq datasets came from different studies, we tested the possibility that the expression differences resulted from external factors like rearing conditions and examined SC expression from RNA-seq of studies where flies were reared in different environmental conditions. In the datasets examined [56][57][58], SC expression shows minimal change in different rearing temperature (Supplementary Figure 15). Additionally, drastic expression divergence of the germlines can be observed in RNA-seq datasets we generated of closely related species reared in the same controlled laboratory condition, including those in the immigrans group and the sister species D. Nevertheless, these expression patterns reveal that despite the essential roles in regulating crossovers, germline transcriptional regulation of many SC genes is highly labile and constantly evolving, echoing their protein and copy number evolution.…”