Patterns of genetic variation in native and non-native populations of European catfish Silurus glanis across Europe

Biological invasions are a major component of global change worldwide. But paradoxically,
an invasive species might also have threatened populations within its native range.
Designing efficient management policies is needed to prevent and mitigate range expansions
of invasive alien species (IAS) in non-native areas, while protecting them within their
native range. Characterizing genetic variation patterns for IAS populations and deciphering
the links between their native and introduced populations is helpful to (i) assess the genetic
state of both native and non-native populations, (ii) reveal potential invasion pathways, (iii)
define IAS management strategies in invaded areas, and (iv) identify native populations
requiring conservation measures. The European catfish (Silurus glanis) is the largest European
predatory fish. Introduced since the seventies from Eastern to Western Europe, it has
colonized many waterbodies. Yet, little is known about the genetic status of non-native
populations and the invasion pathways used by the species. Besides, some native populations
are threatened, requiring conservation actions. Here, we describe current patterns
of genetic variability of native and non-native S. glanis populations across Europe. Using
microsatellite markers, we first assessed genetic variation within and between native and
non-native populations. Second, we performed genetic clustering analyses to determine the
genetic structure of multiple catfish populations across Europe and highlight their potential
links. We revealed that native populations are more genetically diverse than non-native
populations, and highlight complex introduction pathways involving several independent
sources of introduction, which likely explain the invasion success of this large predatory
fish across western Europe.