Ecology and distribution of ostracods associated with flowing waters in the eastern Iberian Peninsula

Abstract

The ostracod fauna of the three main rivers of the central Mediterranean slope of the Iberian Peninsula was studied, with special attention being paid to ecology and distribution. Forty-six stations were sampled in spring and autumn 1995 and thirty ostracod species were collected, two of these (Trajancypris serrata and Heterocypris reptans) new to the Iberian fauna. The most common species were Ilyocypris bradyi, Herpetocypris brevicaudata, Cypridopsis vidua, and Limnocythere inopinata. Cluster analysis showed that these species, together with Ilyocypris inermis and Sarscypridopsis spp. form the most widespread ostracod assemblage in the area, although its widespread distribution is not related to any of the environmental variables monitored. However, factors such as altitude, mean January air temperature, distance from source, flow discharge, water quality, and degree of organic pollution play an important role in explaining the occurrence of less common species. One species group was linked to high elevations and BMWP' biotic index values and low winter temperatures. Candona neglecta best characterizes this assemblage. In the opposite part of this environmental gradient, Ilyocpris gibba, associated with lower attitudes, epitomizes the third species group. Heterocypris salina and Heterocypris incongruens were the species that were most tolerant of organic pollution. Our results are compared with those reported in studies from different habitats (e.g., springs) and latitudes. The implications of our findings for paleoenvironmental reconstruction and water resources management are discussed.