Pushed to the edge: Environmental factors drive ecological responses of <scp> <i>Aphanius fasciatus</i> </scp> when in sympatry with invasive <scp> <i>Gambusia holbrooki</i> </scp>

Interspecific competition may be particularly exacerbated when occurring between native and invasive alien species, with environmental conditions affecting drivers of natural selection shaping spatio-temporal dynamics animal communities. The effects invaders are evident in aquatic ecosystems delicate complex balances, such as Mediterranean coastal wetlands, characterized by unpredictable water flows variable reserves. Understanding how species respond to human-induced biological invasions is paramount importance for planning management measures aiming at conservation purposes. This study investigated whether the occurrence a competing invader resulted changes ecological adaptations comparing two wetland fish species: eastern mosquitofish Gambusia holbrooki killifish Aphanius fasciatus concern. hypothesis was tested sampling fishes Ramsar site central Italy, over 2 years. Generalized linear mixed models were used examine relation parameters presence its putative competitor. aim determine salinity, temperature, depth influenced abundance sympatry mosquitofish. Both probability increased but this increase stronger present. Increasing temperature associated higher respectively, although effect small. salinity acted synergistically characterizing population structure species. Living most extreme stressed environments, potentially risk extinction. These results highlight considering interplay multiple abiotic stressors combined comparative data increasingly critical aid efforts.