Experimental evaluation of preferences of an invasive Ponto-Caspian gammarid Pontogammarus robustoides (Amphipoda, Gammaroidea) for mineral and plant substrata

Abstract

Pontogammarus robustoides has spread across Europe since the second half of the twentieth century. It is often regarded as a psammophilous and/ or phytophilous species. We studied preferences of P. robustoides for 5 mineral substrata of different grain sizes, 5 plant species and 3 artificial plants differing in leaf shape. We tested 10 gammarid individuals in 24-h pairwise choice tests in darkened tanks. Adults selected stones of 27 ± 4.8-mm grain diameter, rather than smaller or larger objects, whereas juveniles preferred particles of 15 ± 3.2-mm grain diameter. Structurally complex plants (natural and artificial) were most preferred for both age groups. Juveniles, unlike adults, preferred natural plants over artificial ones and mineral substrata. Adults preferred mineral materials over macrophytes and did not differentiate between natural and artificial plants. Juveniles did not avoid areas occupied by adults, but in their presence exhibited significantly stronger preferences for substrata providing them with suitable shelters. Habitats selected by gammarids in our study somewhat differed from those commonly used in the field, indicating their high plasticity. Different preferences of adults and juveniles may help them avoid competition and/or cannibalism in the field.

The art of choice: predation risk changes interspecific competition between freshwater amphipods

“…Both species preferred rocky substrata over sand, which is an ineffective shelter against environmental dangers for amphipods (Poznańska et al 2010). These observations corroborate the previous studies carried out on the tested gammarids (Devin et al 2003;MacNeil et al 2008;Jermacz et al 2015).…”

“…D. villosus is known for its preferences for coarse hard substrata (MacNeil and Platvoet 2005;MacNeil et al 2008). Also P. robustoides has been recently found to select stone substratum rather than sand (Jermacz et al 2015). Therefore, we could expect that both species would compete for the same habitat in our experimental design.…”

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

“…Fine sand and silt particles lack the interstitial spaces that are essential in the provision of refuge from higher predators (particularly fish) and are therefore most likely to be the least preferred habitat substrate of amphipods. Resource partitioning can enable the co-existence of multiple invasive species within the same area, with organisms modifying their diet and switching to another habitat type to avoid competition (Robinson and Wilson 1996;Jermacz et al 2015). It is therefore likely that within Pitsford reservoir C. pseudogracilis has already been displaced from coarse grained substrates and has become restricted to less suitable habitats.…”

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

“…In the field, animals can use stones, woody debris or plants as flow refuges. Both studied species are associated with such objects (Kley et al, 2009;Jermacz et al, 2015) and showed the ability to utilize shelters (i.e. the downstream mesh) to stay within the flow zone at a flow of 15 cm/s.…”