Data from: Postglacial recolonizations, watershed crossings and human translocations shape the distribution of chub lineages around the Swiss Alps

Background: Distributions of European fish species were shaped by
glaciations and the geological history of river networks until human
activities partially abrogated the restrictions of biogeographical
regions. The nearby origins of the Rhine, Rhone, Danube and Po rivers in
the Swiss Alps allow the examination of historical and human-influenced
patterns in fish genetic structure over a small geographic scale. We
investigated these patterns in the widespread European chub (Squalius
cephalus) from the Rhone, Rhine and Danube catchments and its proposed
southern sister species Italian chub (Squalius squalus) from the Po
catchment. Results: A phylogenetic tree constructed from mitochondrial
Cytochrome b and COI sequences was consistent with earlier work in that it
showed a separation of European chub and Italian chub, which was also
reflected in microsatellite allele frequencies, morphological traits and
shape differences quantified by geometric morphometrics. A new finding was
that the predominant mitochondrial haplotype of European chub from the
Rhine and Rhone catchments was also discovered in some individuals from
Swiss populations of the Italian chub, presumably as a result of human
translocation. Consistent with postglacial recolonizations from multiple
refugia along the major rivers, the nuclear genetic structure of the
European chub largely reflected drainage structure, but it was modified by
watershed crossings between Rhine and Rhone near Lake Geneva as well as
between Danube and Rhine near Lake Constance. Conclusion: Our study adds
new insights into the cyprinid colonization history of central Europe by
showing that multiple processes shaped the distribution of different chub
lineages around the Swiss Alps. Interestingly, we find evidence that
cross-catchment migration has been mediated by unusual geological events
such as drainage captures or watershed crossings facilitated by retreating
glaciers, as well as evidence that human transport has interfered with the
historical distribution of these fish (European chub haplotypes present in
the Italian chub). The desirable preservation of evolutionarily distinct
lineages will thus require the prevention of further translocations.