Using genome skimming to investigate the mega-diversity of the stygobiont genus Metastenasellus (Crustacea, Isopoda) in African groundwater

1. Research objectives The project proposes to test the "genome skimming" approach on the isopod genus Metastenasellus in African groundwater, in order to produce complete or nearly complete mitochondrial and ribosomal DNA sequences that will be used for DNA-based species delimitation aiming to reveal undetected species-boundaries and phylogenetic reconstructions. The results will then be compared with the Operational Taxonomic Units (OTUs) identified as a result of an exploratory study on biological material from Benin and Cameroon based on COI (Benin and Cameroon) and 28S (only Cameroon) sequences, which identified 27 Metastenasellus preliminary species hypotheses (14 in Benin and 13 in Cameroon) in a selection of stations. This project will provide baseline data that, when later combined with morphological analyses and eDNA sequencing, will allow for more reliable estimates of the biodiversity of the Metastenasellus species group, more resolved inferences of their evolutionary history, and thus a better assessment of their usefulness in characterizing subterranean aquatic ecosystems than traditional approaches based solely on morphology. The genus Metastenasellus (Stenasellidae) includes eight species described when writing this project proposal, exclusively from continental groundwater (stygobiontes), and with trans-Saharan distribution, with one species known from Algeria and 7 others distributed in West and Central Africa (DRC, Cameroon, Ivory Coast, Nigeria). Although groundwater is now known as a major ecosystem in terms of biodiversity, endemism and relict species, this environment remains largely unknown in sub-Saharan Africa, due to a lack of studies and a deficit in taxonomic expertise. The discovery of 27 potential species in Benin and Cameroon, after only a first exploratory study, confirms this observation. 2. Material and methods • Benin: 199 samples with Stenasellidae, 1 to 197 specimens per sample (16,0 on average), 81 DNA extractions, 49 COI sequences. Samples stored in a freezer at -20 °C at the RBINS. • Cameroun: 96 samples with Stenasellidae, 44 DNA extractions, 21 and 27 COI and 28S sequences, respectively. Samples stored in a freezer at -20 °C at the ULB. This study fits into a broader framework that uses stygofauna as an indicator of water quality. It is currently the subject of on-going CEBioS GTI projects, in collaboration with the University of Abomey-Calavi (Benin), which aims to combine taxonomic research with issues of poverty reduction and global climate change. The latter project has already provided interesting patterns of species diversity and distribution for groundwater oligochaetes (Annelida). These objectives have also recently started to be addressed at ULB in the frame of an ARES-sponsored postdoctoral fellowship to Dr. Raoul Kayo, now assistant professor at the University of Bamenda in Cameroon, during which the molecular diversity of Cameroon subterranean isopods was investigated.