DOI: 10.5061/dryad.18931zczc
title: Genetic relationships between sympatric and allopatric Coregonus ciscoes in North and Central Europe

description: Background Sympatric speciation along ecological gradients has been
 studied repeatedly, in particular in freshwater fishes. Rapid post-glacial
 ecological divergence has resulted in numerous endemic species or
 ecologically distinct populations in lakes of the temperate zones. Here,
 we focus on the Baltic cisco (Coregonus albula) complex, to study the
 genetic similarity among two pairs of sympatric autumn- and
 spring-spawning populations from post-glacial German Lakes Stechlin and
 Breiter Luzin. For comparison, we included a similar pair of sympatric
 populations from the Swedish Lake Fegen. We wanted to explore potential
 genetic similarities between the three sympatric cisco population pairs in
 the three lakes, to evaluate whether the pairs may have emerged
 independently in the three lakes, or whether two different species may
 have colonized all three lakes independently. Furthermore, we considered
 allopatric C. albula populations from three Polish, three Finnish, and
 four Swedish locations, and added one Siberian population of the sister
 species C. sardinella and a Swedish C. maraena (whitefish)
 population. By genotyping nine microsatellite markers in 655 individuals
 from these 18 populations, we wanted to elucidate how strongly the cisco
 populations differ across a larger geographical area within Europe.
 Finally, we compared the genetic differences between the spring- and
 autumn-spawning populations of ciscoes in the two German lakes to infer
 the potentially deteriorating effect of strong anthropogenic pressure on
 the lakes. Results Dendrogram, Principal Coordinate Analysis and admixture
 analysis all indicated strong correspondence between population
 differentiation and geographical location for most cisco populations in
 Europe, including the Siberian population of C. sardinella. However,
 populations from some Swedish lakes deviated from this general pattern, by
 showing a distinct genetic structure. We found evidence for independent
 evolution of the three sympatric population pairs because the populations
 co-occurring in the same lake were always most closely related. However,
 genetic differentiation was weak in the two German population pairs, but
 strong in the Swedish Lake Fegen, indicating that the weak differentiation
 in the German pairs reported earlier has eroded further. Conclusions Our
 results suggest that the genetic differentiation at neutral genetic
 markers among populations of the Baltic cisco complex has evolved (and is
 maintained) by random genetic drift in isolated populations. However,
 earlier studies on the Swedish populations combining mitochondrial DNA and
 microsatellite data indicate that also post-glacial immigration from
 separate glacial refugia has shaped the present genetic population
 structure. The low neutral differentiation of the German sympatric pairs
 in contrast to the Swedish pair suggests that recent anthropogenic effects
 on the lakes in Germany may put the endemic spring-spawners at risk to
 extinction.
description: The dataset originates from merging previously published data
 from Swedish populations (Delling B, Palm S, Palkopoulou E, Prestegaard T.
 Genetic signs of multiple colonization events in Baltic ciscoes with
 radiation into sympatric spring- and autumn-spawners confined to early
 postglacial arrival. Ecol Evol<i> </i>2014; 4(22):4346-4360.)
 with newly analysed data from German, Polish, Finnish and Russian
 populations. Because samples were analyzed on different sequencers, eight
 individuals were analysed on both sequencers. The systematic differences
 in read lengths per microsatellite between the sequencers were used to
 align the Swedish data to the new dataset, by adding the difference in
 read lengths to each sample from the Swedish data.
description: NA is coded by 0 (zero)