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Abstract.  In mid latitudes, such as the Mediterranean region, one consequence of global climate change will be a progressive shift of permanent to temporary water courses, altering the life histories of present species or making them disappear. Presented here is a study on the life history of a mayfly species, Serratella ignita, in two Mediterranean streams, one permanent and one temporary. The research focuses on life history parameters such as life cycle, nymphal growth pattern, feeding type, biomass and secondary production. The life cycle was univoltine, showing a fast seasonal nymphal growth during four months in the permanent stream and five months in the temporary stream, with a long egg stage with diapause. The cumulated day-degrees during nymphal growth were similar between streams. Both populations behaved mainly as gatherer-collectors, but the population from the temporary stream also played an important role as a scraper. Animal matter was also consumed by nymphs from both populations. Gut content analysis showed that both S. ignita populations were opportunist/generalists, where changes in diet were correlated with size. Biomass and secondary production were notably higher in the permanent stream, but they were also high in the temporary stream. These data show that S. ignita had a high fitness in both streams. Our results support the idea that species such as this one may cope with future global climate change by maintaining, or even increasing, their populations at the expense of more stenoecic species. [ABSTRACT FROM AUTHOR]