Differences in the functional responses of four invasive and one native crayfish species suggest invader‐specific ecological impacts

Invasive non-native species represent a leading threat to global freshwater biodiversity and crayfish frequently cause extensive ecological damage. However, the extent which their impact: (1) depends on invader identity (2) differs from natural state with native remains unclear. Comparison of functional responses invasive represents promising approach in this regard. Here, we explored whether four (calico Faxonius immunis, spiny-cheek limosus, signal Pacifastacus leniusculus, marbled Procambarus virginalis) European freshwaters most widespread (noble Astacus astacus) overlap function potential effects key resources benthic food webs. First, impact gammarids zebra mussels was assessed by means comparative response analysis using ratio as metric; second, consumption macrophytes (Chara sp.) detritus (leaf litter) quantified compared feeding experiments. Both invader- resource-specific were observed. calico exhibited strongest per capita mussels, respectively, ratios being 2-fold higher than those noble crayfish. Marbled showed an intermediate effect both prey species, whereas had lower impacts In experiment, consumed highest amount detritus, while did not differ among five species. Our work demonstrates as-yet unrecognised differences North American invaders The lack congruence across observed suggests mostly species-specific pattern stresses importance resource when considering An initial assessment invader-specific positions impactful invaders.