Shift of grey seal subspecies boundaries in response to climate, culling and conservation.
Identifying the processes that drive changes in the abundance and distribution of natural populations is a central theme in ecology and evolution. Many species of marine mammals have experienced dramatic changes in abundance and distribution due to climatic fluctuations and anthropogenic impacts. However, thanks to conservation efforts, some of these species have shown remarkable population recovery and are now recolonizing their former ranges. Here, we use zooarchaeological, demographic and genetic data to examine processes of colonization, local extinction and recolonization of the two northern European grey seal subspecies inhabiting the Baltic Sea and North Sea. The zooarchaeological and genetic data suggest that the two subspecies diverged shortly after the formation of the Baltic Sea approximately 4200 years bp, probably through a gradual shift to different breeding habitats and phenologies. By comparing genetic data from 19th century pre-extinction material with that from seals currently recolonizing their past range, we observed a marked spatiotemporal shift in subspecies boundaries, with increasing encroachment of North Sea seals on areas previously occupied by the Baltic Sea subspecies. Further, both demographic and genetic data indicate that the two subspecies have begun to overlap geographically and are hybridizing in a narrow contact zone. Our findings provide new insights into the processes of colonization, extinction and recolonization and have important implications for the management of grey seals across northern Europe.
Evolutionary Genomics Section, Centre for Geogenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.|Marine Evolution and Conservation, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
Katharina
K
Fietz
Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
Anders
A
Galatius
Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
Jonas
J
Teilmann
Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
Rune
R
Dietz
Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway.
Anne Kristine
AK
Frie
Department of Animal Behaviour, University of Bielefeld, PO Box 10 01 31, 33501 Bielefeld, Germany.
Anastasia
A
Klimova
Marine Evolution and Conservation, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
Per J
PJ
Palsbøll
Fisheries and Maritime Museum, Tarphagevej 2, DK-6710 Esbjerg V, Denmark.
Lasse F
LF
Jensen
Scottish Oceans Institute, School of Biology, University of St Andrews, Fife KY16 9TH, UK.
Jeff A
JA
Graves
Department of Animal Behaviour, University of Bielefeld, PO Box 10 01 31, 33501 Bielefeld, Germany.
Joseph I
JI
Hoffman
Evolutionary Genomics Section, Centre for Geogenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.
Morten Tange
MT
Olsen
D000818:Animals; D001454:Baltic States; D002980:Climate; D003247:Conservation of Natural Resources; D004463:Ecology; D005060:Europe; D053476:Extinction, Biological; D005828:Genetics, Population; D009659:North Sea; D046048:Seals, Earless / Q000145:classification*; D062211:Spatio-Temporal Analysis
Baltic Sea; Halichoerus grypus; admixture; local extinction; recolonization