Genome-Wide Divergence Among Population Pairs of Parasitic and Non-Parasitic Lampreys (Lampetra fluviatilis and L. planeri)

The degree of speciation between the European ‘paired’ species Lampetra planeri (Lp) and Lampetra fluviatilis (Lf) is unclear as these taxa are morphologically and phylogenetically very similar and may represent two ecotypes of a single species. We investigated the level of gene flow between Lf and Lp populations in France using population genetics (13 microsatellites loci) and genomics (RAD sequencing) approaches. We aimed at i) comparing the estimates of gene flow between sympatric Lf and Lp populations obtained with microsatellite and RAD markers and ii) identifying RAD loci putatively involved in the adaptive divergence between species. Results based on the microsatellite genotyping of 665 individuals from six river systems revealed moderate to strong levels of gene flow between Lf and Lp populations sampled in the same rivers. Estimates of genetic differentiation were much higher among Lp than Lf populations with the latter displaying higher levels of genetic diversity. Overall, these results support the hypothesis that Lf and Lp are two ecotypes of a single species but common garden experiments are required to validate this hypothesis. These results also suggest that the connectivity between Lp and Lf populations should be restored to maintain high levels of genetic diversity in Lp populations.