Genetic diversity of Irish kelp (Laminaria hyperborea)

The below is a synopsis of Kathryn M. Schoenrock, Aisha M. O’ Connor, Stéphane Mauger, Myriam Valero, João Neiva, Ester Á. Serrão & Stacy A. Krueger-Hadfield (2020) Genetic diversity of a marine foundation species, Laminaria hyperborea (Gunnerus) Foslie, along the coast of Ireland, European Journal of Phycology, 55:3, 310-326, DOI: 10.1080/09670262.2020.1724338

Changing sea temperatures are predicted to affect kelp populations, driving a poleward shift in the distribution of European kelp species. Therefore, understanding the genetic diversity of Irish kelp populations has never been more important. Genetic diversity underlies the ability of a population or species requires to adapt to environmental change. Genetic diversity manifests as differences in phenotype (physical appearance), for example eye or hair colour in humans, and non-visible characteristics like heat tolerance. The genetic composition of a population can be measured using microsatellite loci which can tell us the number of alleles (for loci), allele frequencies, and incidence of heterozygosity. Ideally populations would have high genetic diversity, allowing the community to respond positively to natural and manmade stressors, such as ocean warming, through natural selection.

As part of the KelpRes project a team of researchers from NUI Galway, the University of Alabama, Sorbonne Université and the Universidade do Algarve published a paper in January 2020 looking at the genetic diversity of 8 populations of Cuvie (Laminaria hyperborean) in Ireland.

Map of sites at which samples were collected, reproduced from Schoenrock et al 2020

Lough Hyne had the highest heterozygosity as measure in the study and may have functioned as a climatic refugia in the Celtic Sea during past glaciation periods. This high genetic diversity could make it an important source of propagules for maintaining genetic diversity in kelp populations on the south coast of Ireland.

They also found that there are more significant genetic differences between sites separated by greater distances (isolation by distance); for instance two site in Co. Galway (An Cheathrú and Leitir Mealláin) were more similar at 20 km apart than two sites 80 km apart. This would suggest that there is not significant transfer of kelp propagules over distances 80 km, though this probably depends on local tidal and oceanic currents.

As can be seen from the diagram below Irish sites are genetically distinct from sites in Brittany France, but that there is also greater genetic structure in populations along the west coast of Ireland.

Diagram showing grouping of kelp populations reproduced from Schoenrock et al 2020

While the work of KelpRes continues to understand the functioning of kelp ecosystems in Ireland across 40 newly sampled populations, this preliminary study is a fascinating insight into L. hyperborea populations on the west coast of Ireland.

Glossary of genetics terms

The genetic composition of a population is usually measure in terms of allele frequencies, number of alleles or heterozygosity.

Locus – Site on a chromosome where a particular gene occurs

Alleles – Different variants of DNA sequence at the same locus, simply different forms of a gene

Heterozygote: An individual with two different alleles at a locus