AQUATIC COLEOPTERA AND HETEROPTERA ASSEMBLAGES IN WATERBODIES FROM EPHEMERAL COASTAL STREAMS (RAMBLAS) OF SOUTH-EASTERN SPAIN

A total of 63 species of aquatic Coleoptera (45) and Heteroptera (18) were collected between 1991 and 1994 from 25 sites in the coastal drai nage network of semiarid south-eastern Spain (Murcia Province). The ar ea is drained by ephemeral streams locally known as ''ramblas'', which are wide, usually dry, channels flowing only in flash-flood events, a lthough in some reaches small permanent or temporary streams, springs, and pools can be formed by either groundwater seepage in the stream b ed or by wastewaters from human activities. These waterbodies are ofte n saline (salinity >3 g/l) and suffer from floods and droughts. The st udied waterbodies were grouped into four types according to their orig in: 1) groundwater-fed habitats, 2) urban wastewaters, 3) agricultural wastewaters, and 4) marine pools. A first ordination of all the sites clearly separated groundwater-fed habitats from wastewaters and marin e pools. The two first axes of a second ordination, with only groundwa ter-fed habitats, showed a strong correlation with salinity, type of a quatic vegetation and water permanence. These variables, particulary s alinity, were the major environmental factors explaining species distr ibution. Finally, most of the species recorded are of biogeographical and/or ecological interest, some being considered as locally endemic.