Evolution of amphi-boreal marine fauna

Risto Väinölä, Finnish Museum of Natural History

Project summary (2009-2012)

The study will address the biogeographical history and composition of the marine fauna of northern latitudes on a circum-boreal scale, and particularly in the North European marginal seas, using a toolset of molecular systematics and population genetics that allows a new level of resolution to trace details of faunal relationships.

Much of the North Atlantic boreal fauna shows externally close relationships to the North Pacific. These relationships between faunas have been thought either to date back to warmer, pre-Pleistocene times (>2 million years ago; the “great trans-Arctic interchange”) or to reflect very recent or on-going trans-Arctic faunal connections; but only in few instances any solid evidence of the dynamics of connections exist. Prompted by recent observations, we set out a new working hypothesis of a common occurrence of repeated isolation–re-invasion cycles between the two oceans during the Pleistocene climatic fluctuations. That would have led to repeated contacts of two or several differentiated invading lineages, to secondarily meet in the North European seas. When hybridisation has taken place, a new kind of diversity would have been created as a synthesis of that accumulated in temporary inter-oceanic isolation. To probe this hypothesis, the study will involve a comparative phylogeographic assessment of several amphi-boreal and boreal-arctic fish and invertebrate taxa, using mitochondrial and nuclear marker genes. It will also involve targeted studies of post-contact hybridisation in specific cases.

This is fundamental research which will shed light on the effects of climatic fluctuations on the dispersal opportunities of species across the Arctic basin in the past and in the future. It also addresses the hypothesis that hybridisation and its outcome, “speciation-in-reverse”, may have had an important role in the post-glacial build-up of marine communities, or as a consequence of human interference in recent years. The study is topical for understanding and predicting the dynamics of very basic biological phenomena in a situation where the Arctic dispersal opportunities are now very rapidly changing because of climate amelioration and changing navigation practices, which are about to reset the established post-glacial natural zoogeography.