Salinity-related distribution of alien amphipods in rivers provides refugia for native species

Abstract

There are numerous papers upon the range extension, biology and the impact of alien amphipods upon the local fauna. However, there are no studies concerning the alien versus native species distribution patterns at the catchment scale of river systems. In total 125 sites were sampled: 41 in main rivers constituting the Polish section of the central invasion corridor (Bug, Vistula, Notec with canals, Oder) and 84 in their affluents. The conductivity of large rivers was much higher than in their small affluents. The number of alien species and their abundance was higher at sites with raised conductivity values. The reverse situation was noticed when native amphipods were taken into account. Moreover, large rivers were inhabited by alien fauna, whereas in smaller streams only native species were sampled. The absence of alien amphipods in small rivers may be explained by their ecological preference for a higher conductivity of water. Thus in smaller streams the native fauna is free from the pressure posed by alien amphipods. If not degraded by human activity, small affluents may function as refugia for native amphipod species. Otherwise, elevation of salinity related to improper catchment management or sewage treatment may lead to extinction of such local disjunct population of native amphipods.

Abiotic factors affecting habitat selection by two invasive gammarids Dikerogammarus villosus and Pontogammarus robustoides

“…Conductivity is a good measure of water salinity (Wagner et al, 2006) and has been used in other studies on amphipod distribution (Grabowski et al, 2009). We used a glass y-maze ( Fig.…”

“…calcium necessary for molluscan shells and crustacean cuticles (Lampert & Sommer, 2007). Salinity varies horizontally near river outlets to the sea and where affluents enter larger rivers of different ionic contents (Rozengurt, 1971;Grabowski et al, 2009). Raised ionic content may be beneficial for alien species adapted to brackish water and/or unstable salinity conditions (Devin & Beisel, 2007).…”

“…We expected that gammarids originating from brackish water habitats (Rozengurt, 1971) would exhibit preferences for increased ionic content in water (Piscart et al, 2005), preventing them from entering small, more freshwater affluents of large rivers (Grabowski et al, 2009). We also assumed that both species would select lentic sites (Devin & Beisel, 2007;Borza et al, 2017), but that P. robustoides, as a more common inhabitant of stagnant waters (Ja_ zd_ zewski et al, 2002) would be relatively less adapted to flow.…”

Environmental and morphological factors influencing predatory behaviour by invasive non-indigenous gammaridean species

“…However, interference competition for shelter can also play a role (Van Riel et al 2006, 2007, 2009Platvoet et al 2009a). These processes are influenced by body size, while in the field, habitat heterogeneity is also important, as heterogeneous habitats provide refuges that may prevent total replacement (MacNeil et al 2008;Grabowski et al 2009;Kestrup and Ricciardi 2009;Piscart et al 2009;Platvoet et al 2009a;Van Riel et al 2009). …”

Climate change as a possible driver of invasion and differential in HSP70 expression in two genetically distinct populations of the invasive killer shrimp, Dikerogammarus villosus

“…The problem of mass colonisation by alien amphipods applies to most of major European rivers, such as Danube, Rhine, Rhone, Vistula, Oder, and their main tributaries as well as to major artificial waterways joining different river systems such as Mittelland Kanal in Germany (Ja_ zd_ zewski and Konopacka 2000; Bij de Vaate et al 2002;Bollache et al 2004;Ja_ zd_ zewski et al 2005;Grabowski et al 2007aGrabowski et al , 2009). The newcomers not only successfully outcompete, but also eliminate the native amphipods and other macroinvertebrates (Dick and Platvoet 2000;Ja_ zd_ zewski et al 2004;Grabowski et al 2009). If compared to native, the invasive amphipod species are characterized by several specific life history traits, such as high fecundity, early maturation, and high number of generations per year, which enable them to colonize successfully new water basins (summarized by Grabowski et al 2007b).…”