Abstract
Approximately ten to 15 generations after first inoculation, two invasive goby species Neogobius melanostomus and Ponticola kessleri have dispersed and established rapidly the upper Danube River. Population genomic amplified length polymorphism (AFLP) data show that the genome of the more recent newcomer, i.e. the globally invasive N. melanostomus, is significantly differentiated to a comparatively large degree (~ 5%) and exhibits pronounced small-scale population structure along a recently invaded 200 km river section. MtDNA haplotype identity over N. melanostomus samples suggests that an admixture of phylogenetically strongly differentiated source populations is unlikely. Fine-scaled local genetic population structure of N. melanostomus as deduced from Bayesian assignment tests suggest a trisection of the upper Danube instead of a clinal pattern: one downstream sample is assigned together with distant upstream samples to one population cluster. A second cluster comprises central samples, whereas two samples from the margins of this central region appear to have mixed ancestry. AFLP genome scan results indicate this population structure is strongly correlated with extrinsic (geographic) parameters, i.e. migration barriers of anthropogenic origin. However, divergence of at least one AFLP locus correlates positively with a proxy for trophic differentiation, i.e. variation of white muscle δ 15 N stable isotope signature. In contrast to N. melanostomus, no significant population differentiation was detectable in P. kessleri along the analyzed invasion pathway. In genome scans of P. kessleri, variation of a single locus is strongly positively correlated with an extrinsic parameter combination but not with any ecological parameter.
Highlights
Invasive species, by definition, arrive, establish and spread in novel environments within very short time frames (Keller et al 2011)
Contemporary evolution and invasion success is hypothesized to be shaped to a large degree by intrinsic characteristics of the source populations (Lambrinos 2004; Björklund and Almqvist 2010), and effects of propagule pressure (Allendorf and Lundquist 2003; Lockwood et al 2005; Colauti et al 2006), inbreeding (Nei et al 1975; Young and Seykora 1996), phenotypic plasticity (Parker et al 2003), life history traits (Tsutsui et al 2000) and migration and dispersal abilities (Sakai et al 2001; Phillips et al 2006)
Fragment Length Polymorphism (AFLP)) and to a smaller extent mtDNA data, we investigate baseline population genetics, ancestry and admixture of the upper Danube goby populations and assess the general hypothesis that intraspecific differentiation of two sympatric invasive goby species has developed on a small geographical scale in about ten generations after first introduction
Summary
By definition, arrive, establish and spread in novel environments within very short time frames (Keller et al 2011). Contemporary evolution and invasion success is hypothesized to be shaped to a large degree by intrinsic characteristics of the source populations (e.g. number and genetic constitution of introduced specimens) (Lambrinos 2004; Björklund and Almqvist 2010), and effects of propagule pressure (Allendorf and Lundquist 2003; Lockwood et al 2005; Colauti et al 2006), inbreeding (Nei et al 1975; Young and Seykora 1996), phenotypic plasticity (Parker et al 2003), life history traits (Tsutsui et al 2000) and migration and dispersal abilities (Sakai et al 2001; Phillips et al 2006). Genetic bottlenecks and founder effects can promote and restrict the speed of adaptive evolution (Tsutsui et al 2000; Colautti et al 2004; Stepien and Tumeo 2006; Prentis et al 2008). In human-mediated introductions (Kolbe et al 2004; Therriault et al 2005; Roman and Darling 2007), and at frontend expanding sites (Price and Sol 2008) differentiation is widespread and can occur within short time frames
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