Dominant littoral invertebrates of North European marginal seas: dynamic genetic changes and their ecological consequences

A project of the Baltic Sea Research Programme BIREME.

The project explores past and ongoing changes in the systematic and genetic composition of dominant invertebrate taxa of the littoral and benthic habitats of North European marginal seas, and the consequences of these changes on the ecology of populations and communities. The research addresses a so far largely neglected level of marine biodiversity: species or lineages, which have escaped traditional morphological identification but can be detected using molecular marker characters. Many widespread organisms are subdivided into geographically and ecologically distinct but morphologically similar units (taxa) on a circumboreal scale. In the process of the current trans- and inter-oceanic biotic interchange, invasions by such cryptic taxa tend to remain masked, even though they would involve a factual replacement of a native taxon, or lead to hybridization and introgression between the lineages and thus to a loss of their original systematic, genetic and ecological identities.

This study will document the history of putatively recent, cryptic invasions by closely related, alien sister taxa of the dominant littoral molluscs of the Baltic, White and Barents Sea coasts, and analyse the patterns and dynamics of hybridisation, introgression and amalgamation of the native and invading lineages (Atlantic and Pacific genomic origins). The principal objects are the bivalves Macoma and Mytilus, for which previous evidence of systematic heterogeneity and of multiple invasions of the area exist. We employ multiple classes of molecular markers (mtDNA, nuclear enzyme loci, noncoding nDNA); analyse in parallel similar but independent hybrid zones (or hybrid swarms) in different regions; and assess invasion events and secondary contact zones of different ages. Genetic analyses are accompanied by assessment of the ecological performance (fitness) of the various mollusc lineages and their hybrids in different environments.

The project is carried out as a collaborative effort of Finnish and Russian teams. The Finnish team bears the main responsibility of the molecular studies, and the Russian team of population ecology.

Team leaders:

Dr. Risto Väinölä, Finnish Museum of Natural History, University of Helsinki

Dr. Petr Strelkov, St. Petersburg State University