TSOI - A new Index based on Odonata populations to assess the conservation relevance of watercourses in Tunisia

Abstract

Global ecological conditions existing in the streams of northern Tunisia are very unequal. In consideration of their appropriate management and restoration requirements, breeding populations of 28 Odonata species were studied over an annual cycle in twenty-eight watercourses (22 permanent, 6 intermittent). In total, 7 363 larvae and 337 exuviae were collected. We developed a new indicator, the Tunisian Stream Odonatological Index (TSOI), to assess conservation aspects of Odonata biodiversity in African Mediterranean streams by analysing dragonfly communities. The TSOI operates at the species level. Taxonomic richness, voltinism, endemism, relative taxonomic distinctiveness, and regional conservation status (IUCN) are elements taken into account to design this index. Accordingly, presence of both Maghreb endemic and semivoltine species (Calopteryx exul, Platycnemis subdilatata, Aeshna cyanea, Boyeria ¡rene, Gomphus lucasii, Onychogomphus costae, O. forcipatus, and O. uncatus) may provide useful information about the refuge quality of each habitat type for species with different biological features, and their interest level from a conservation point of view. The results of a first application of this approach are presented in the paper as well. As far as we know, a biodiversity conservation index based on benthic invertebrates in the African Mediterranean area has never before been proposed nor used.