Comparative Analysis of Predatory Behavior of Invasive Alien Dikerogammarus villosus (Sowinsky, 1894) and Native Gammarus varsoviensis Jazdzewski, 1975 Amphipods

Resumo

Alien species of amphipods were registered in Belarus in the early 2000s. Over many years of observing the structure of the riverine macrozoobenthos community, a decrease in the frequency of occurrence of indigenous amphipod species in the southern part of Belarus was noted. In order to find an explanation of the current process, a laboratory experiment was conducted to study the predatory effect of the invasive alien (Dikerogammarus villosus (Sowinsky, 1894)) and native (Gammarus varsoviensis Jazdzewski, 1975) species of amphipods on some macrozoobenthos groups to compare the values of predation rates of amphipods and interspecific interaction of the two amphipod species. During the experiments on the food selectivity, it was found that invasive alien and native species of amphipods consumed the same number of macrozoobenthos groups. The maximum values of the predation rate of amphipods were determined when they consumed water louse and mayfly larvae; there were no statistically significant differences found. The average values of the predation rate of the invasive alien species were lower when it consumed adults of G. varsoviensis than young of G. varsoviensis. On the basis of the experimental data, it can be assumed that the direct predatory pressure of D. villosus or another similar alien species of amphipods (for example, D. haemobaphes (Eichwald, 1841)) is one of the main reasons for the disappearance of G. varsoviensis from the river sections where it was previously found.