Do temporary streams of Mediterranean islands have a distinct macroinvertebrate community? The case of Majorca

Abstract

Insular streams suffer from similar forms of environmental degradation that occur in continental systems. However, the intrinsically fragile nature of insular ecosystems, together with their exceptional conservation value, makes them particularly vulnerable. Streams on the Mediterranean island of Majorca (Spain) dry annually during summer, with the period of flow permanence ranging from a few (two - three) to several (six - seven) months. Moreover, humans have greatly influenced the landscape of this island, reducing the extent and quality of the riparian vegetation. This study investigates the associations between natural flow variability, riparian land use and water quality with the structure of macroinvertebrate communities of temporary streams of the island of Majorca. Overall, the patterns of faunistic similarity showed that land use and flow permanence are decisive factors shaping the structure of the macroinvertebrate communities inhabiting these streams. Taxa richness was higher in undisturbed spring-fed sites, surrounded by Mediterranean climatic vegetation, than in disturbed sites, affected by urban or rural uses. However, abundance of macroinvertebrates was highest in the sites with a longer period of flow permanence, independent of land use. We also conclude that the springs feeding streams with a longer flow period represent a potential refuge for a high number of the endemic and relict species of macroinvertebrates, particularly those located in well-preserved areas. In fact, in spite of the insularity and the absence of permanent running waters, macroinvertebrate taxa richness in these spring-fed streams compared well to that in similar mainland streams. These results indicate that even though insular assemblages are more distinct than those in continental systems, the temporary streams existing on Majorca are not especially depauperate in terms of taxa richness.