Crustaceana

Mauchart, Péter; Bereczki, Csaba; Ortmann-Ajkai, Adrienne; Csabai, Zoltán; Szivák, Ildikó

doi: 10.1163/15685403-00003355pmid: N/A

<jats:p>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 native<jats:italic>Gammarus fossarum</jats:italic>and the naturalized<jats:italic>G. roeselii</jats:italic> — are distributed among microhabitats, depending on their sympatric or allopatric distribution. We hypothesized that the larger body-sized species (<jats:italic>G. roeselii</jats:italic>), 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. Although<jats:italic>G. fossarum</jats:italic>is 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.<jats:italic>Gammarus roeselii</jats:italic>occurred 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.</jats:p>