Conservation of freshwater biodiversity in Tunisia in a climate change context: combining amphipod distribution data and molecular analyses to improve priorities

The exceptional diversity of freshwater fauna of the Mediterranean Basin currently faces a crisis in which climate change combined with overexploitation of freshwaters heavily threatens the local fauna. In this context, it is urgent to define conservation priorities on how to best protect freshwater biodiversity. One of the main limits to define such actions remains the lack of knowledge in many countries. In this study, we test the usefulness of molecular data (COI gene) combined with morphological identification to better predict the pattern of biological diversity and threats of climate change on freshwater biodiversity. We focused our study on the freshwater amphipods as model organisms in order to define conservation strategies in Tunisia, one of the most threatened countries. Our results confirmed that amphipods diversity is largely underestimated with nine species identified by their morphology and 33-39 species assigned depending on delimited with the most parsimonious molecular delimitation method. The distribution of amphipods is mainly restricted to the northern part of Tunisia and seems to be positively correlated with precipitation and negatively correlated with thermal amplitudes and precipitation fluctuations. These environmental factors are sensitive to climate change and confirm that conservation strategies need to be redefined and adjusted in the face of future climate predictions. Moreover, the total diversity and spatial distribution patterns provided by molecular methods seem to be more detailed and accurate than results based on morphology alone and nicely complement traditional species assignment.