Diversity and ecology of aquatic insects (Ephemeroptera, Plecoptera and Trichoptera) in the Martil basin (Northwestern Morocco)

The current study aimed to examine the responses of Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa to the major physicochemical (temperature, pH, electrical conductivity, dissolved oxygen, biological oxygen demand, chemical oxygen demand) and hydro-morphological (stream width, water depth and current speed) factors affecting their abundance, richness and distribution. Immature insects of Ephemeroptera, Plecoptera and Trichoptera were sampled as well as water during eight seasonal surveys conducted at 19 stations in Martil basin from spring 2016 to spring 2018. In total, 10,370 individuals belonging to 22 families, 36 genera and 48 species were collected during the study period. Baetidae, Perlodidae and Hydropsychidae were the most abundant and diversified families, respectively for each order. Significant biotypological differences of the EPT assemblages were observed among stream types relating to their spatial distribution, hydrological features and pollution levels. However, species richness and abundance were positively correlated with DO, pH and altitude and negatively correlated with temperature and the other parameters measured. The taxonomic list compiled following our recent investigations includes six new species for the Martil basin enabling them to expand their range in northern Morocco. Furthermore, the biogeographical analysis shows that EPT taxa from Martil basin are essentially composed of Mediterranean elements, with a high proportion of Ibero-Maghrebian endemic species. Moreover, this study provides a basis for further studies to analyze the distribution patterns of EPT taxa through multi-dimensional approaches.