Aim To analyse the importance of local and regional influences on the patterns of species richness in natural and man-made lakes and to infer the impacts of human-mediated introductions on these patterns.
Methods Species occurrence data were gathered for 25 natural and 51 man-made lakes. Analysis is based on regression models of local richness against their related regional richness and lake environmental variables.
Results Local native richness was mostly controlled by the regional richness. Conversely, local total richness was mainly explained by local variables. These statements apply to both natural and man-made lakes. Lacustrine systems displayed weak resistance to invaders.
Main conclusions Species introductions have apparently contributed to saturate fish communities in these systems even if no clear negative effect on the survival of native species (i.e. species extinction) is detectable so far.