Chironomid (Diptera, Chironomidae) species assemblages in northeastern Algerian hydrosystems

Abstract

The aim of this paper was to analyze the distribution of chironomids (Diptera, Chironomidae), and determine their substrate preferences, from two hydrosystems located in northeastern Algeria: the Kebir-East and the Seybouse wadis. Sixty-five species were recorded in 49 sampling sites distributed along the main courses of the two hydrographic nets and their tributaries. The majority of taxa comprised cosmopolitan species widely distributed along these two hydrosystems. <em>Cricotopus</em> (<em>Cricotopus</em>) <em>bicinctus</em> showed the highest abundance and frequency of occurrence (29.52%) and was widespread in almost all the sampling sites. Species richness ranged from 4 to 23, Shannon diversity between 0.15 and 0.90, Evenness from 0.23 to 1. A cluster analysis was carried out to represent the different groups of sites sharing similar species composition. Agglomerative cluster analysis grouped the sampling sites into four clusters according to the community data. An Indval analysis was then carried out to detect indicator species for each group of the sampling sites. <em>Cricotopus</em> (<em>Isocladius</em>) <em>sylvestris</em> was indicator of the first group of the sampling sites. <em>Orthocladius pedestris</em>, <em>Rheocricotopus chalybeatus</em> and <em>C. bicinctus</em> were indicators of the second group, and <em>Polypedilum cultellatum</em> of the third group. The fourth group was not characterized by any species. Indval analysis allowed also to determine species preferences for substrate size: <em>Corynoneura scutellata</em> and <em>Dicrotendipes nervosus</em> emphasized a preference to fine gravel, and <em>Glyptotendipes pallens</em> to fine sand.