Worldwide, kelp populations are stressed by warming, increased storms and other man-driven disturbances. Marine population distributions are projected to retreat poleward with climate change if they cannot adapt to changing conditions, which would potentially lead to a regime shift in subtidal habitats. In Northern Europe, Laminaria hyperboreais a subtidal ecosystem engineer whose distribution has shifted over millennia, leaving predicted areas of high genetic diversity from the last glacial maximum (LGM) near its southern distribution limit in the Iberian Peninsula. In Ireland, L. hyperborea structures communities by supporting diverse faunal assemblages and producing large quantities of organic carbon throughout the year. We investigated the genetic diversity of eight populations ranging from the southern coast to the northwest of Ireland using nine microsatellite loci. Diversity was found to be highest in Lough Hyne, a Special Area of Conservation (SAC), near the predicted climate refugium. We found evidence of isolation by distance, with high connectivity between populations that were geographically close, likely driven by short range dispersal of L. hyperboreapropagules. Genetic diversity (measured as expected heterozygosity and allelic richness) was highest at Lough Hyne, and decreased northwards, as predicted from past range shifts. Expected heterozygosity was highest at Lough Hyne (0.706) and decreased northward, with the lowest value at Bridges of Ross (0.283). Based on these patterns, further fine-scale investigation into population diversity, dispersal and potential resilience in Irish kelp forests are necessary as warming and non-native species are observed more and more frequently.

DNA was extracted from kelp samples and six microsatellite loci previously developed forL. digitata (Ld148, Ld158, Ld167, Ld531, Ld704; Billot et al.2003)and six loci developed for L. ochroleuca (LoIVVIV-23, LoIVVIV-17, LoIVVIV-28, LoIVVIV-27, LoIVVIV-24; Coelhoet al.2014)were used. We amplified locus Ld531 in a simplex PCR and the remaining loci in three multiplexes (M1: Ld148, Ld158, Ld167; M2: LoIVVIV-17, LoIVVIV-24; M3: LoIVVIV-23, LoIVVIV-28, LoIVVIV-27). 

These data have been calibrated across capillary sequencing platforms at UAB, CCMAR, and SBR. Please use conversion metrics from this article in order to compare Lh data across labs.

However, we have updated these files and all future usage for combining data across platforms should use the file called Lh_genalex_2020.csv.