Interference competition between alien invasive gammaridean species

Abstract

The relative abundances of gammaridean species in the river Rhine have profoundly changed since the invasion of Dikerogammarus villosus in 1994/1995. This study tested whether these changes in gammaridean dominance could have been determined by interspecific competition and unequal mortality, for example by intraguild predation (IGP). Single and two species tests have been carried out in aquariums provided with all substrata present in the main channel of the Rhine. Changes in substratum choice, increased swimming activity and increased mortality of a species were used as indicators of interspecific competition during interaction between gammaridean species. Interspecific competition and mortality between the most abundant invasive gammaridean species in the Rhine, viz. Gammarus tigrinus, Echinogammarus ischnus andDikerogammarus villosus were tested. In singlespecies experiments, G. tigrinus and D. villosus showed similar preferences for a stony substratum, whereas E. ischnus mostly occupied the water column. The two-species aquarium experiments indicated direct interference competition for substratum and unequal mortality between G. tigrinus and D. villosus, with D. villosus being the stronger competitor. Competitive stress was influenced by population density, was size-dependent and varied between the different types of substratum due to substratum choice. G. tigrinus did not show any behaviour indicative of interference competition in the presence of E. ischnus, and neither did E. ischnus or D. villosus in the presence of any of the other gammarideans. Swimming in the water layer may already enable E. ischnus to minimise its encounters with the stone-dwelling D. villosus and G. tigrinus. To maximise the encounters between E. ischnus and D. villosus, a fish (Lepomis gibbosus) was added to occupy the water layer during the aquarium experiments. E. ischnus showed a higher mortality in the presence of both D. villosus and fish, probably due to increased stress, as shelter opportunities to escape the predators had been minimised. The study shows that interference competition between gammaridean species can explain the replacement of the North American invader G. tigrinus by D. villosus in the river Rhine. E. ischnus and D. villosus both PontoCaspian invaders did not show interference competition in our experiments and co-exist in the Rhine.

Substrate preferences of coexisting invasive amphipods, Dikerogammarus villosus and Dikerogammarus haemobaphes, under field and laboratory conditions

“…These results support the findings of previous studies centred on D. villosus (Devin et al 2003;Hesselschwerdt et al 2008;Kley et al 2009;Van Riel et al 2009) but also extend our knowledge of substrate preferences for D. haemobaphes.…”

“…Consequently, smaller individuals often utilize smaller particle sizes which may also serve as refuge from predators (MacNeil et al 2008). The limited number of experimental studies conducted, and which are primarily focussed on D. villosus, suggest that invasive amphipods have a stronger affinity for large cobble habitats (Van Riel et al 2009;Kobak et al 2015). However, little is known about how habitat preferences may vary in mixed populations of congeners.…”

The river Rhine: a global highway for dispersal of aquatic invasive species

“…In addition, human disturbances may prevent strong interspecific competition by native species. Competitive stress between native and invasive species is strongly influenced by local environmental circumstances, such as type of substratum, water temperature, salinity, current velocity and habitat heterogeneity (MacNeil et al 2001(MacNeil et al , 2003(MacNeil et al , 2004Wijnhoven et al 2003;Palmer and Ricciardi 2004;MacNeil and Platvoet 2005;Kestrup and Ricciardi 2009;Van Riel et al 2009). The ongoing rise in water temperature in the river Rhine due to thermal pollution and global warming will also affect the establishment success of non-indigenous species and interspecific competition (Leuven et al 2007).…”

“…Existing databases on the distribution of non-indigenous species in the Delta Rhine (Den Hartog and Van der Velde 1987;Van den Brink et al 1990) were updated and extended with data on other river sections, using a distribution atlas on freshwater molluscs (Gittenberger et al 1998), recent field surveys (Kelleher et al 1998;Rajagopal et al 2000;IKSR 2002;Bij de Vaate 2003;Bernauer and Jansen 2006;Bij de Vaate et al 2006, 2007 Van der Velde et al 2000Van Riel 2007;Van Riel et al 2009). During these field surveys specimens were cautiously brushed from artificial substrate (marbles), riprap and groyne stones, and subsequently preserved in 70% ethanol, sorted by species and counted in the laboratory.…”

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). …”