Maltseva A.L.1*, Panova M.A.Z.2, Varfolomeeva M.A.1, Vikhreva D.V.1, Smutin D.V.3, Pavlova P.A.1, Maslakov G.P.1, Danilov L.G.3, Mikhailova N.A.4, Granovitch A.I.1 2022. Phylogeography of the closely related Littorina (Neritrema) species in the North-East Atlantic // Invertebrate Zoology. Vol.19. No.4: 404–424 [in English].

1 Department of Invertebrate Zoology, St Petersburg State University, St Petersburg, Russia.

2 Department of Marine Sciences - Tjдrnц, University of Gothenburg, Sweden.

3 Department of Genetics and Biotechnology, St. Petersburg State University, St. Petersburg, Russia.

4 Centre of Cell Technologies, Institute of Cytology Russian Academy of Sciences, St Petersburg, Russia.

* Corresponding author:

Arina Maltseva: ORCID 0000-0003-1973-4728

Marina Panova: ORCID 0000-0002-4147-6473

Marina Varfolomeeva: ORCID 0000-0003-0887-8486

Polina Pavlova: ORCID 0000-0002-3213-1967

Georgii Maslakov ORCID 0000-0003-0462-7284

Lavrentii Danilov ORCID 0000-0002-4479-3095

Natalia Mikhailova: ORCID 0000-0003-1650-9330

Andrei Granovitch: ORCID 0000-0002-5203-104X

doi: 10.15298/invertzool.19.4.05

ABSTRACT: Phylogeographic studies of evolutionary young species co-existing over a vast geographic area can provide insights in the process of evolutionary divergence and its cohesiveness in different parts of the species ranges. The Littorina snails of the ‘saxatilis’ cryptic group diverged in near-glacial time, and tend to live in sympatry. L. saxatilis is widely distributed on both sides of the North Atlantic, while L. arcana and L. compressa are patchy distributed on the shores of Europe and Atlantic islands. The biogeographic history of the Littorina ‘saxatilis’ cryptic group is still obscure, with L. saxatilis studied much better than the other two species. We evaluated the population structure of the three ‘saxatilis’ species on the coasts of Wales, the Norwegian and the Barents seas using several genetic markers:  the mitochondrial cytochrome b gene (cytb, partial, 26 haplotypes for 268 sequences), nuclear (5 microsatellite loci in 458 individuals) and whole-genome (2bRAD, 63 417 loci in 114 individuals) markers.

Analyses based on the cytb and microsatellite markers showed a deep divergence between the British and the North European populations of all three species with a high genetic similarity between their sympatric populations from Wales. L. compressa had the highest differentiation from both L. arcana and L. saxatilis and demonstrated the clear population structure due to allele frequency. The degree of the genetic differentiation between sympatric L. arcana and L. saxatilis in some regions was lower than between the regions within a species. Moreover, analyses of all three types of used markers indicate that the continental populations of L. arcana include individuals with contrasting genomic profiles.

Our results suggest that L. arcana and L. compressa separated from their common ancestor L. islandica after L. saxatilis. The three sibling species survived glaciation in a refugium (or refugia) on the British coasts, separated from the mainland refugium (or refugia). After the glaciation, L. compressa colonised the mainland, most likely from a single European refugium. Post-glacial continental repopulation by L. arcana could have occurred from at least two sources, with two differentiated lineages still recognisable. Further inclusion of Littorina populations from South Norway and France is needed to complete the reconstruction of biogeographic history in these three evolutionary young species of Littorina snails.

KEY WORDS: phylogeography, cryptic species, sympatric speciation, Littorina, cytochrome b, microsatellites, 2bRAD.

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