Ecological speciation in postglacial European whitefish: rapid adaptive radiations into the littoral, pelagic, and profundal lake habitats.
Understanding how a monophyletic lineage of a species diverges into several adaptive forms has received increased attention in recent years, but the underlying mechanisms in this process are still under debate. Postglacial fishes are excellent model organisms for exploring this process, especially the initial stages of ecological speciation, as postglacial lakes represent replicated discrete environments with variation in available niches. Here, we combine data of niche utilization, trophic morphology, and 17 microsatellite loci to investigate the diversification process of three sympatric European whitefish morphs from three northern Fennoscandian lakes. The morphological divergence in the gill raker number among the whitefish morphs was related to the utilization of different trophic niches and was associated with reproductive isolation within and across lakes. The intralacustrine comparison of whitefish morphs showed that these systems represent two levels of adaptive divergence: (1) a consistent littoral-pelagic resource axis; and (2) a more variable littoral-profundal resource axis. The results also indicate that the profundal whitefish morph has diverged repeatedly from the ancestral littoral whitefish morph in sympatry in two different watercourses. In contrast, all the analyses performed revealed clustering of the pelagic whitefish morphs across lakes suggesting parallel postglacial immigration with the littoral whitefish morph into each lake. Finally, the analyses strongly suggested that the trophic adaptive trait, number of gill rakers, was under diversifying selection in the different whitefish morphs. Together, the results support a complex evolutionary scenario where ecological speciation acts, but where both allopatric (colonization history) and sympatric (within watercourse divergence) processes are involved.
Department of Arctic and Marine Biology, University of Tromsø Tromsø, N-9037, Norway.
Kim
K
Præbel
Department of Arctic and Marine Biology, University of Tromsø Tromsø, N-9037, Norway.
Rune
R
Knudsen
Department of Arctic and Marine Biology, University of Tromsø Tromsø, N-9037, Norway.
Anna
A
Siwertsson
Department of Biosciences, University of Helsinki PO Box 65, Helsinki, FI-00014, Finland.
Markku
M
Karhunen
Department of Environmental Sciences, University of Helsinki PO Box 65, Helsinki, FI-00014, Finland ; Kilpisjärvi Biological Station, University of Helsinki Käsivarrentie 14622, Kilpisjärvi, FI-99490, Finland.
Kimmo K
KK
Kahilainen
Department of Biosciences, University of Helsinki PO Box 65, Helsinki, FI-00014, Finland.
Otso
O
Ovaskainen
Department of Biology, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo PO Box 1066, Blindern, Oslo, N-0315, Norway ; Department of Forestry and Wildlife Management, Hedmark University College Campus Evenstad, Elverum, NO-2418, Norway.
Kjartan
K
Ostbye
Department of Arctic and Marine Biology, University of Tromsø Tromsø, N-9037, Norway.
Stefano
S
Peruzzi
Department of Arctic and Marine Biology, University of Tromsø Tromsø, N-9037, Norway.
Svein-Erik
SE
Fevolden
Department of Arctic and Marine Biology, University of Tromsø Tromsø, N-9037, Norway.
Per-Arne
PA
Amundsen
Coregonus lavaretus; gill raker; phenotype–genotype correlation; postglacial fish; reproductive isolation