Évolution spatio-temporelle des diptères dans les oueds d’Aurès et Biskra

Abstract

This work seeks to study the spatio-temporal distribution of Diptera in three wadis in the Aurès region taking into account the physicochemical characteristics of the waters of these wadis. 16 sampling sites were prospected along El Abiod Wadi, Abdi Wadi and El Haï Wadi from January 2008 to December 2009. The fauna counted includes 37128 individuals corresponding to 43 taxa belonging to 17 families, expressing an important richness in the region. The Chironomidae family has the highest abundance, manifested in particular by the predominance of Orthocladiinae with 13503individus (36.37%), then we find the Simuliidae species which was the most diversified family (seven nominal and complex species) whose the most abundant are Simulium gr.aureum (5405individus, 14,56%), S. gr. ornatum (5142individus, 13.85%) and S.pseudequinum (2668individus, 7.19%). Orthocladiinae have a wide spatio-temporal distribution, constitutes with the other Chironomidae taxa, the first elements that are reinstalling after a long drying periods or after floods. The highest numbers are recorded in Dj, In, Mn and Fed2, accounting for 47.71% of the total fauna, while the taxonomic richness is higher in the Mn, Fed2, Haï2 and Dj sampling sites. The spatio-temporal monitoring of the physicochemical parameters reveals a normal water quality in the three wadis, with the exception of the highly polluted sampling site of El Haï wadi (Til) which receives excessive discharges of wastewater from the Aïn Touta city. The statistical analyzes exploited by PCA and FCA show a certain zonation from upstream to downstream in our rivers, 3 distinct groups on the factorial planes: headwaters sampling sites which take refuge alticoles taxa preferring fresh waters, those of the middle course which shelter the eurythermic rheophilous taxa and the lower course sampling sites which lodge the thermophilic taxa. In order to define the environmental parameters controlling the spatial distribution of the recorders Diptera, an CCA has been realized. The obtained results indicate that our population is classified as: high-altitude rheophilous taxa preferring fast currents and cold waters: M.blanci, Clinocera sp., Chelifera sp., Chrysops sp., S. gr. ornatum, Atylotus sp. sp., Rhabdomastix sp., Wiedemannia sp., Ulomyia sp., Tonnoirella sp., Hybomitra sp., Heamatopota sp., Leptoconops sp., Tipula sp., Tipula ( Yamatotipula) sp., Tipula (Acutipula) sp., Psychoda sp. and Setacera sp.; thermophilic taxa of average to low altitude wich support a high concentrations of mineralization: S. ruficorne, S.velutinum, S.sergenti, Chrysopilus sp., Ochtera sp., Ephydra sp., Silvius sp. and Tabanus sp.; eurytopic taxa broadly distributed manifeste indifferently to environmental conditions: S.pseudequinum, S. gr. aureum, Dasyhelea sp., Chironomus sp. and finaly taxa preferring calm waters: Anopheles sp. and Culex sp.