Spatio-temporal distribution of simuliids (Diptera) and associated environmental factors in two Mediterranean basins of Southern Spain

Abstract

The distribution of simuiiid species in rivers Guadaira and Guadaiete (south of the Iberian Peninsula) is examined in reiation to some associated environmental factors. The most abundant and widespread species in the study area were Simulium velutinum, Simulium intermedium and Simulium pseudequinum, whereas Simulium lineatum, Simulium ruficorne and Metacnephia blanci were very rare. Stepwise multiple regression revealed that S. velutinum was positively influenced by chemicai oxygen demand, whereas S. pseudequinum and S. sergenti depended on altitude (negatively) and current veiocity (positiveiy). The coefficient of correlation between distance between sites and Jaccard's index of simiiarity of the sites showed that the simuiiid community at different sites changed as a direct function of distance. Simulium xanthinum was found only at higher altitude sites, where water quaiity was best. Most of the remaining species were opportunistic. The number of simuiiid species in the basins of rivers Guadaira and Guadalete was lower than that reported for other, nearby basins. The similarity in species composition between these basins was low. © Asociación Española de Limnología.