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Rivers in Mediterranean high mountains are especially vulnerable to climate change because these areas are characterized by extreme climatic conditions of snowy winters and relatively frequent summer droughts. Climate induced alterations in temperature and the magnitude of high and low river flows are expected to have significant effects on aquatic fauna. Here, we analysed changes in the caddisfly communities of the Sierra Nevada during a 20-year period on an altitudinal gradient range of 952–3050 m. Furthermore, we related these changes to an observed increase in air temperature and decrease in river flow over the last 40 years. Overall, caddisfly species richness increased but patterns varied depending on altitude in a non-linear shape. Richness increased in altitude with maximum values at sites of intermediate-high altitude (1800–2000 m). The effects of the observed climate change may be explained by the colonization of headwaters and middle reaches from mid-lowland species or by those from streams and rivers in nearby mountain chains at lower altitude. The observed richness increase and its association with environmental conditions suggest that mountains with a considerable altitudinal gradient may function as refuges for species and populations during periods of climatic change, which strength the importance of the conservation of mountainous habitat.

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.