Biogeography, ecology, and conservation of mayfly communities of relict mountain streams, north-eastern Algeria

Data on Maghrebian mayfly communities are scarce and fragmentary, but evidence of alterations of the North African riverine landscape depleting the freshwater biota is rapidly mounting. In contrast to the overexploited lowlands, the highlands of north-eastern Algeria are hotspots of freshwater biodiversity and the last refugia to micro-endemics, North African endemics, and Eurosiberian relicts. The mayflies of relict mountain streams of north-eastern Algeria were investigated and 20 species or taxa in five families were recorded. Two species of the genus Habrophlebia and one species of Centroptilum are new to science, whereas two Rhithrogena species are new to Algeria, including the Numidian endemic Rhithrogena sartorii. Co-inertia analysis suggested a highly significant co-structure between mayfly assemblages and habitats defined by altitude, flow velocity, bed width, water depth, and water conductivity. In addition, a Poisson generalized linear model indicated a strong positive relationship between species richness and water depth and a weaker negative one with bed width (stream size). The results are congruent with the hypothesis that habitat provides the templet that drives mayfly communities, and they support the use of mayflies as bioindicators in the implementation of monitoring schemes to assess the ecological integrity of Maghrebian freshwater biodiversity hotspots. The upstream part of the Kebir-East river basin is subjected to forest fires, pollution, and flow alteration, whereas the downstream part, which includes the vast Mekhada marsh, is increasingly fragmented and invaded by alien fish species. Conservation efforts focusing on the management of Oued Kebir-East, a transboundary Maghrebian river, and the restoration of the Mekhada marsh, a Ramsar site, need to be launched during the United Nations Decade on Ecosystem Restoration (2021-2030).