Square pegs in round holes - the implications of shell shape variation on the translocation of adult Margaritifera margaritifera (L.)

1. The freshwater pearl mussel Margaritifera margaritifera is endangered throughout Europe.

2.Historically, mussels were described on the basis of shell characteristics. In more recent years with the advent of molecular techniques many ‘species’ of molluscs have been found to be ecophenotypes.

3.The pearl mussel is found in numerous rivers throughout Ireland and the UK with varying degrees of superficial differences. It is has been thought that the most divergent form is found in the Nore River, Ireland, Margaritifera m. durrovensis.

4.The current investigation considers shell shape differences (using morphometrics — elliptic Fourier descriptors) in mussels from a variety of rivers in Ireland in relation to river pH.

5.Results suggest that M. margaritifera has a fairly plastic phenotype, with a gradient of shape change in relation to water pH.

6.Margaritifera m. durrovensis does not appear to be morphologically unique from other populations studied, instead occurring at one end of the shell shape gradient.

7.
Findings also suggest that shell shape may be characteristic to individual rivers. The existence of phenotypically distinct groups of Margaritifera margaritifera has particularly important implications for the future conservation of the species.

8.Ex situ conservation and reintroduction efforts will need to consider both the genotypic and phenotypic suitability of mussels if translocation is to be used as a viable conservation tool in the future. Copyright © 2010 John Wiley & Sons, Ltd.