New paper published in Marine Genomics on the evolutionary history of synaptophysins

Atlantic cod (photo: K. Præbel)
Atlantic cod (photo: K. Præbel)

In this study, we aimed at gaining more knowledge of the enigmatic role of the synaptophysins in the adaptive evolution of stationary and migratory populations of Atlantic cod (Gadus morhua L.).

The synaptophysin protein family consists of membrane proteins involved in vesicle-trafficking events, but the physiological function of several members is unknown. Notably, a member of the synaptophysins, pantophysin (Pan I), has been shown to be highly polymorphic among populations of Atlantic cod and we have also previously revealed that the stationary and migratory ecotypes of Atlantic cod display near fixed alleles at this locus (e.g. Fevolden et al 2012). The divergence between the ecotypes of Atlantic cod at this locus has been suggested to reflect local adaptation, e.g. to alternative regimes of light, during settling of the YOY and to vertical behavior of the adults. However, whether the adaptive divergence between the ecotypes at the Pan I locus is caused by “divergence hitch-hiking” of Pan I with other genes/synaptophysins (e.g. rhodopsin, known to be directly linked to perception of alternative wavelengths of light) or by directional selection against unfavorable Pan I alleles during settling and vertical migration also remains to be illuminated. Additionally, in order to understand the adaptive significance of these genes, we also need a better understanding of the evolution of the gene family and whether the protein phenotypes produced by the allelic variants differ in composition.

Phylogeny of the synaptophysin gene family (Andersen et al. 2015).

The study was led by Øivind Andersen, Nofima and together with several other collaborators we showed that the synaptophysin gene family may have expanded in vertebrates via four successive gene duplications. We did not identify any major structural differences in between allelic variants of the Pan I protein, suggesting that the adaptive importance of these allelic protein variants, by them self, may be of limited functional importance. The genomic distance between Pan I and rhodopsin was mapped to >2.5Mb, but we identified highly significant linkage disequilibrium between these two physins when genotyping the ecotypes of shallow and deep water juvenile settlers. This suggests that Pan I alleles may have been fixed via selection on other strongly linked genes. This was further supported by the similar predicted allelic variants of rhodopsin proteins.

Although we did not settle the long lasting puzzle of the Pan I divergence between ecotypes of Atlantic cod, this study propelled our understanding of adaptive loci (such as Pan I) forward and seeded important new directions for understanding of adaptive population divergence in marine species.

 Evolutionary history and adaptive significance of the polymorphic Pan I in migratory and stationary populations of Atlantic cod (Gadus morhua). Available from Marine Genomics


New paper published in Conservation Genetics on fauna crime

Smelt (photo: Finn Gregersen)

This paper is the outcome of the Master thesis of MSc Mari Hagenlund that Kjartan Østbye and I supervised. Mari tested the hypothesis that the recent occurrence of Smelt (Osmerus eperlanus) in lake Storsjøen (Norway) is a result of intentional stocking. It is though that smelt have been stocked in the lake to increase the growth of brown trout (Salmo trutta), an important recreational fish species. Such stocking is illegal in Norway and we and others have previously shown how an invader within only one or two decades may destabilize an entire ecosystem and cause e.g. speciation reversal (See Bhat et al. 2014).

Comparing  genetic variation (microsatellites) from smelt samples collected from all the possible post-glacial invasion routes (natural colonization) and samples collected in neighbor lakes (intentional stockings), the paper concludes that the smelt in lake Storsjøen most likely is a result of introduction from the large Lake Mjøsa, and that a significant number (>100) of individuals may have been stocked.  We did not identify any effects of bottlenecking in the lake Storsjøen population, but identified indications of a recent population expansion. This indicates that the smelt has been a successful invader.

This paper provides important information for nature managers in how to handle future reports on intentional stockings and allow for planning of strategies of prosecution in cases of fauna crime. It also illustrates the power of genetic tools in nature management.

All laboratory analyses and subsequent genotyping were performed at the genetic lab at UiT.

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