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Free keywords:
competitive exclusion; gene flow; hybridization; local adaptation; pike-perch; secondary contact
Abstract:
In addition to ecological factors, evolutionary processes can determine the invasion
success of a species. In particular, genetic admixture has the potential to
induce rapid evolutionary change, which can result from natural or humanassisted
secondary contact between differentiated populations. We studied the
recent range expansion of zander in Germany focusing on the interplay between
invasion and genetic admixture. Historically, the rivers Elbe and Danube harboured
the most north-western source populations from which a north-westward
range expansion occurred. This was initiated by introducing zander outside its
native range into rivers and lakes, and was fostered by migration through artificial
canals and stocking from various sources. We analysed zander populations of
the native and invaded ranges using nuclear and mitochondrial genetic markers.
Three genetic lineages were identified, which were traced to ancestral ranges.
Increased genetic diversity and admixture in the invaded region highlighted
asymmetric gene flow towards this area. We suppose that the adaptive potential
of the invading populations was promoted by genetic admixture, whereas competitive
exclusion in the native areas provided a buffer against introgression by
novel genotypes. These explanations would be in line with evidence that hybridization
can drive evolutionary change under conditions when new niches can be
exploited.
