Global molecular variation of <i>Paramecium jenningsi</i> complex (Ciliophora, Protista): a starting point for further, detailed biogeography surveys

The world’s second stand of <i>P. primjenningsi</i> (<i>Paramecium jenningsi</i> complex, Ciliophora, Protista), heretofore known only from India, has been revealed in Ethiopia (Africa). This finding has enlarged the range of this cryptic species and was a trigger to re-analyse the distribution of all members of the complex (known from ∼20 tropical locations). The current survey is an initial one, where, based on haplotype networks, a detailed analysis of the relationship within the <i>P. jenningsi</i> complex has been performed. Although the V4 hypervariable fragment of the SSU rDNA gene is widely used as a first-step barcode marker for microbial HTS analyses, it has provided inconclusive results based on the dataset investigated. However, the ITS1-5.8S-ITS2-5’rDNA and COI mtDNA fragments indicate the possibility of the delimitation of the cryptic species of <i>P. jenningsi</i> (which is crucial from the point of view of metabarcoding surveys). We suppose that future sampling of unexplored, tropical regions will certainly change our knowledge about <i>Paramecium</i> biodiversity and biogeography. This sampling will probably rely on the integration of metabarcodes from environmental DNA studies, with molecular data obtained from identified representatives of particular cryptic species.