Blue mussels - Mytilus edulis and M. trossulus



Species Number of genetic studies Baltic population structure Baltic population diversity Baltic effective population size Temporal data Genetic risks Management recommendations

Blue mussels:
Mytilus  trossulus and M. edulis (see text below about species status) 

>10 Continuous, strongly differentiated, and influenced from hybridization (see text below about hybridization)  Genetic composition unique for the Baltic populations of the species  Unknown but presumably very large  Limited  Changes in geographic position and range of hybrid zone. Loss of peripheral populations with strong trossulus profile. 
Monitoring of populations, most intensively in SW Baltic (hybrid zone) and northernmost populations











Mapping Baltic Sea genetic biodiversity

The map shows proportion between M. edulis (blue colour) and M. trossulus  (yellow) as identified with a nuclear DNA marker Me 15/16 in populations.


Summary of key published genetic information

Mytilus edulis and M. trossulus are sometimes considered subspecies of the same species and sometimes separate species. The reason for this is that they show many distinct features and remain separate entities in many parts of their worldwide distributions, but at the same time they hybridize extensively in zones of contact and are thus not reproductively isolated from each other. The origin of M. trossulus is in the Pacific, and after entering the N Atlantic through the Bering Strait 3.5 million years ago, it gave rise to M. edulis. Today Baltic populations of Mytilus are a thorough mix of hybridizing M. edulis and M. trossulus. Hybridization occurs mainly in the Danish Straits but to some extent also east of the Straits. Baltic populations of Mytilus have a genetic composition that is unique for this region. The BaltGene programme has mapped the nature of the complex genomes of Baltic Mytilus and found a mosaic-like mix of M. edulis and M. trossulus genes being involved. Mitochondrial DNA (mtDNA, both maternally and paternally transmitted in mussels!), of Mytilus populations inside the Baltic Sea is very similar to M. edulis and is believed to derive from hybridization between Baltic populations and North Sea M. edulis. However, other genetic characteristics are unique for the Baltic populations and of M. trossulus origin

Key publications

Burzyński A, Zbawicka M, Skibinski DOF, Wenne R (2003) Evidence for recombination of mtDNA in the marine mussel Mytilus trossulus from the Baltic. Molecular Biology and  Evolution 20:388-392. PubMed

Kijewski T, Zbawicka M, Väinölä R, Wenne R (2006) Introgression and mitochondrial DNA heteroplasmy in the Baltic populations of mussels Mytilus trossulus and M. edulis. Marine Biology 149:1371-1385. 


Kijewski T, Śmietanka B, Zbawicka M, Gosling E, Hummel H, Wenne R. 2011. Distribution of Mytilus taxa in European coastal areas as inferred from molecular markers. Journal of Sea Research, 65: 224-234


Riginos C, Cunningham CW (2005) Local adaptation and species segregation in two mussel (Mytilus edulis x Mytilus trossulus) hybrid zones. Molecular Ecology 14:381-400. PubMed


Väinölä R, Strelkov P (2011) Mytilus trossulus in Northern Europe. Marine Biology 158,4: 817-833 


Zbawicka M, Burzyński A, Wenne R (2007) Complete sequences of mitochondrial genomes from the Baltic mussel Mytilus trossulus. Gene 406: 191-198. PubMed


Śmietanka B, Burzyński A, Wenne R. (2010). Comparative genomics of marine mussels (Mytilus spp.) gender associated mtDNA: rapidly evolving atp8.J. Mol. Evol. 71: 385 – 400. PubMed



CONTRIBUTOR (January 2012)
Roman Wenne
, Polish Academy of Science, Institute of Oceanology, Sopot, Polen

Responsible editor: Roman Wenne
, Polish Academy of Science, Institute of Oceanology, Sopot, Polen 
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