Dietary niche divergence between two invasive fish in Mediterranean streams

Clarifying the mechanisms associated with the coexistence of invasive species is important to understand the overall impact of multiple invasions on recipient communities. Here we examined whether divergence or convergence in dietary niche occurred when invasive Lepomis gibbosus and Australoheros facetus coexist in Iberian streams. We used stomach content analyses to determine dietary niche composition, width, and overlap in allopatric and sympatric counterparts in the Lower Guadiana throughout the dry-season. The variations in dietary niche between pumpkinseed and the cichlid were consistent with predictions derived from the niche divergence hypothesis. Although there were no changes in the use of plant material from allopatry to sympatry in either species, sympatric pumpkinseed and the cichlid displayed marked shifts in the use of animal prey and a decrease in niche width relative to allopatric counterparts. Moreover, sympatric pumpkinseed and cichlid showed similar niche width but differed significantly in plant and animal prey use. Taken together these results suggest that divergence in dietary niches may play a role in mediating coexistence of multiple invaders in Iberian streams