Genomic divergence, introduction history and latitudinal adaptation of grass carp

4 1 Understanding the genomic signatures of population differentiation is fundamental to obtain a 4 2 comprehensive view of the evolutionary process of organisms. Grass carp is one of the most 4 3 important fish species in the world due to its significant value in aquaculture and worldwide 4 4 vegetation biocontrol. However, little is known about the contemporary population structure 4 5 and also the genetic basis of adaptation to a wide range of latitudinal environments. Using 4 6 43310 SNPs generated by genotyping by sequencing in 197 grass carps from nine 4 7 populations, we examined the patterns of population differentiation, historical introduction 4 8 and evidence of local selection. The overall genetic differentiation across all native 4 9 populations was unexpectedly low. Nevertheless, these native populations were clearly