Population Genomics and Local Adaptation of Invasive Sea Lamprey (Petromyzon marinus) in the Great Lakes

Sea lamprey (Petromyzon marinus) is an invasive species in the Laurentian Great Lakes, where it has caused significant damage to fisheries. Knowledge of tributary streams acting as sources of sea lamprey is needed to maximize effectiveness of control efforts. We used RAD-seq to assess the genetic distinctiveness of larval sea lampreys collected in tributaries across different eco-regions in the Great Lakes basin. We used SNP data to test the following hypotheses: (1) sea lampreys are genetically homogeneous among streams; (2) a few SNPs scattered across the genome exhibit signatures of adaptation to local stream conditions; (3) high F_st SNPs can be used to diagnose stream-of-origin of lamprey collected in open lake habitats. Differentiation among localities was generally low for most SNPs (F_st<0.05); however, a few outlier SNPs exhibited significant differentiation among streams, consistent with local adaptation. Two of the outlier loci were located in genes possibly associated with lampricide metabolism and may reflect differences in lampricide treatment history among streams. These data illustrate that high levels of gene flow impact the majority of the genome; however, some loci may be locally adapted. Outlier loci potentially associated with lampricide treatment history are important candidates for future studies of lampricide resistance.