Closely similar species may occupy similar niches, but usually divergence can be found in one or more traits when they inhabit the same habitat. In this study, we examined how two co-occurring gammarids — the nativeGammarus fossarumand the naturalizedG. roeselii — are distributed among microhabitats, depending on their sympatric or allopatric distribution. We hypothesized that the larger body-sized species (G. roeselii), exploiting their advantages in competition, restrict smaller species to microhabitats with smaller particle sizes. Four headwaters were sampled in the Mecsek Mountains (SW Hungary) in May, July and October 2009, and 37 local scale environmental variables at each site were measured. AlthoughG. fossarumis smaller in size, significantly more individuals were collected from the more favourable lithal and biotic microhabitats, whereas a strong negative association was observed between the two species.Gammarus roeseliioccurred at sites characterized by degraded riparian vegetation, which indicates stronger anthropogenic impacts, but still has a disadvantage in competition in mountainous streams under anthropogenic influence.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.