Is Dikerogammarus villosus (Crustacea, Gammaridae) a ‘killer shrimp’ in the River Rhine system?

Abstract

Communities and food web structures of aquatic ecosystems can be strongly affected by the establishment of alien macroinvertebrate species. In many European waters, the invasion of the Ponto-Caspian amphipod Dikerogammarus villosus has led to displacement of other macroinvertebrates. Predation by D. villosus is often assumed to be the key driver of the displacement based on results of laboratory studies, but this has not been verified in the field. Here, we report our investigation of the relevance of D. villosus predation in the River Rhine system using both stable isotope analyses of d 13 C and d 15 N, and molecular analyses of D. villosus gut contents with group-specific primers aiming at macroinvertebrate prey taxa. Stable isotope analyses of D. villosus from ten sites showed mean d 15 N values comparable to those of primary consumers. Overall, only approximately 1% of all tested primer/gut content combinations revealed DNA of the respective taxa. Both indicate minor importance of predation by D. villosus as a driver of the observed macroinvertebrate displacement. Conceivably, competitive strength due to opportunistic feeding, indicated by different niche widths between and a strong intraspecific variation of d 13 C values of D. villosus within sites of our study, is much more important for its invasion success.

Omnivory and stability in freshwater habitats: Does theory match reality?

“…The success of the Ponto‐Caspian amphipod Dikerogammarus villosus (Gammaridae) , one of the 100 worst invasive alien species in Europe (DAISIE ), is at least in part due to its omnivorous feeding strategies. There is some evidence that its success at outcompeting native species may be due to intraguild predation, although the importance of this mechanism in the field is still debated (Koester, Bayer, & Gergs, ; Koester & Gergs, ; MacNeil & Platvoet, ). Arbačiauskas et al.…”

“…In a review of food webs in Mediterranean rivers, Power et al (2013) at least in part due to its omnivorous feeding strategies. There is some evidence that its success at outcompeting native species may be due to intraguild predation, although the importance of this mechanism in the field is still debated (Koester, Bayer, & Gergs, 2016;Koester & Gergs, 2014;MacNeil & Platvoet, 2005). (a) Where the omnivoreconsumer link is much stronger than the consumer-resource link, the indirect positive effect of the omnivore on the resource should outweigh the direct negative effect and a trophic cascade will be observed.…”

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

“…These include rapid growth rates and early sexual maturation. In addition, both taxa exhibit high fecundity which may be up to three times higher than Gammarus pulex, the most widely distributed native amphipod in north-western Europe (Grabowski et al 2007;Bacela et al 2009;Pöckl 2009;Koester et al 2016). Both D. villosus and D. haemobaphes also have strong competitive advantages over native and other established non-native amphipod taxa associated with their opportunistic and flexible omnivorous feeding characteristics (Dick et al 2002;Platvoet et al 2009a;Rewicz et al 2014).…”

Predator diet, origin or both? Factors determining responses of omnivorous amphipods to predation cues

“…This species is often regarded as an omnivore with a strong tendency to predation on macroinvertebrates (Dick & Platvoet, 2000;Dick et al, 2002;MacNeil & Platvoet, 2005). On the other hand, some field studies demonstrated its low trophic position, with a large share of plant food in its diet (Hellmann et al, 2015;Koester et al, 2016). Thus, the feeding habits of D. villosus clearly depend on a number of factors, such as the community structure (Hellmann et al, 2015) or temperature (van der Velde et al, 2009).…”