A novel molecular approach to the study of a mussel hybrid zone on the West Coast of Ireland

2003

YEAR BOOK

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Galway-Mayo Institute of Technology

Brian Coghlan & Elizabeth Gosling

A novel molecular approach to the study of a mussel hybrid zone on the West Coast of Ireland

A typical electrophoresis run distinguishing the Mytilus species and their hybrids. (A. Hae III Digest ladder, B. Hybrid with 184 and 126bp bands. C. 128bp M. galloprovincialis. D. 180bp M. edulis. E. 126bp M. galloprovincialis) Auras below * are unused primer from PCR mix

The shores of the northwestern Atlantic have two indigenous mussel species, the Mediterranean mussel Mytilus galloprovincialis and the Blue mussel Mytilus edulis . These two species, once isolated by the last ice age, are now occurring sympatrically along 1500 miles of the Northwestern Atlantic coast. The two species regularly interbreed and hybridise, producing a mosaic hybrid zone over much of this range.

On exposed west of Ireland shores, M. galloprovincialis occurs predominantly high in the intertidal zone, while M. edulis is more abundant at lower tidal levels. This distribution has remained unexplained. However, it has been hypothesised that factors such as resistance to desiccation, wave exposure, refuge from predators, and primary or secondary selective settlement, act singularly or accumulatively to explain the distribution of M. galloprovincialis in the high intertidal zone.

Until the late 1990s there was no single morphological or genetic diagnostic marker that could unequivocally discriminate between these two species. Now, however, a new nuclear DNA PCR (Polymerase Chain Reaction) based marker has been developed which is not only totally diagnostic but also identifies hybrid individuals (see figure).

With this new marker, we will address the question of whether M. galloprovincialis larvae settle preferentially higher in the intertidal zone, or if the two species redistribute themselves with respect to tidal height after initial larval settlement.

Using these methods, we hope to explore the dynamics of mussel settlement in relation to these two species and investigate the degree of hybridisation occurring in these zones.

The research is funded by the Department of Education's Technological Sector Research Program, Strand 1 (2002-2005).

Contact: Brian Coghlan & Dr Elizabeth Gosling, Molecular Ecology Group, School of Science, Galway-Mayo Institute of Technology, Galway; E-mail: [email protected] , [email protected]