Lophelia pertusa corals from the Ionian and Barents seas share identical nuclear ITS2 and near-identical mitochondrial genome sequences

Jean-François Flot,Mikael Dahl,Carl André

doi:10.1186/1756-0500-6-144

Abstract

BackgroundLophelia pertusa is a keystone cold-water coral species with a widespread distribution. Due to the lack of a mitochondrial marker variable enough for intraspecific analyses, the population structure of this species has only been studied using ITS and microsatellites so far. We therefore decided to sequence and compare complete mitochondrial genomes from two distant L. pertusa populations putatively isolated from each other (in the Barents Sea off Norway and in the Mediterranean Sea off Italy) in the hope of finding regions variable enough for population genetic and phylogeographic studies.ResultsThe mitogenomes of two L. pertusa individuals collected in the Mediterranean and Barents seas differed at only one position, which was a non-synonymous substitution, but comparison with another recently published L. pertusa mitochondrial genome sequence from Norway revealed 18 nucleotide differences. These included two synonymous and nine non-synonymous substitutions in protein-coding genes (dN/dS > 1): hence, the mitogenome of L. pertusa may be experiencing positive selection. To test for the presence of cryptic species, the mitochondrial control region and the nuclear ITS2 were sequenced for five individuals from each site: Italian and Norwegian populations turned out to share haplotypes of both markers, indicating that they belonged to the same species.ConclusionsL. pertusa corals collected 7,500 km apart shared identical nuclear ITS2 and near-identical mitogenomes, supporting the hypothesis of a recent connection between Lophelia reefs in the Mediterranean and in the Northern Atlantic. Multi-locus or population genomic approaches will be required to shed further light on the genetic connectivity between L. pertusa reefs across Europe; nevertheless, ITS2 and the mitochondrial control region may be useful markers for investigating the phylogeography and species boundaries of the keystone genus Lophelia across its worldwide area of distribution.

Highlights

Lophelia pertusa is a keystone cold-water coral species with a widespread distribution
In the northern Atlantic, due to the lack of a mitochondrial marker variable enough for intraspecific studies [20], the population structure of L. pertusa has only been studied using internal transcribed spacer (ITS) sequences [21] and microsatellite markers [21,22,23]. This is unfortunate as mitochondrial markers present numerous advantages over nuclear ones: haploid markers are cheaper and easier to sequence, and have a smaller population size resulting in faster coalescence
We decided to sequence and compare the complete mitogenomes from two individuals originating in locations putatively isolated from each other, in the hope of finding variable mitochondrial regions suitable for population genetic and phylogeographic analyses

Summary

Introduction

Lophelia pertusa is a keystone cold-water coral species with a widespread distribution. We decided to sequence and compare complete mitochondrial genomes from two distant L. pertusa populations putatively isolated from each other (in the Barents Sea off Norway and in the Mediterranean Sea off Italy) in the hope of finding regions variable enough for population genetic and phylogeographic studies. In the northern Atlantic, due to the lack of a mitochondrial marker variable enough for intraspecific studies [20], the population structure of L. pertusa has only been studied using internal transcribed spacer (ITS) sequences [21] and microsatellite markers [21,22,23]. We decided to sequence and compare the complete mitogenomes from two individuals originating in locations putatively isolated from each other (in the Barents Sea off Norway and in the Ionian Sea off Italy), in the hope of finding variable mitochondrial regions suitable for population genetic and phylogeographic analyses

Methods

Results

Conclusion