Warszawa Wrocław Szczecin Gdańsk Olsztyn Kraków Poznań Delimitation of species in Lepocinclis ovum complex (Euglenida) Katarzyna Chaber*, Maja Łukomska-Kowalczyk*, Alicja Fells*, Bożena Zakryś* *Institute of Evolutionary Biology, Faculty of Biology, Biological-Chemical Research Centre, University Of Warsaw Background The aims of the study Materials and methods Results Fig. 3. Consensus Bayesian tree based on 79 nSSU rDNA sequences. (1) significant increase of the number of sequences representing the L. ovum-like taxa on phylogenetic trees; (2) comparative morphological and molecular research on new strains (=isolates); (3) estimation of morphological and genetic diversity and verification of morphological diagnostic features for particular taxa (well-established clades) on a molecular phylogenetic tree; (4) reconstruction of phylogenetic relationships; (5) taxonomic verification, amending diagnoses, and designating epitypes for well-distinguished taxa, particularly for L. ovum and L. globulus. Using environmental sampling and nuclear SSU rDNA sequencing, we delimited species within the group of Lepocinclis ovum-like taxa. Apart from L. ovum and L. globulus, 13 other species were distinguished and four taxa (L. conica comb. nov., L. fominii comb. nov., L. gracilicauda comb. nov., and L. pseudofominii nom. nov.) had their taxonomic ranks changed. For all verified species, diagnostic descriptions were amended and epitypes designated, particularly for L. ovum and L. globulus. Identification of many common species of autotrophic euglenids is still problematic due to unsolved controversies in their taxonomy. Lepocinclis ovum (Ehren.) Lemmermann 1901 and L. globulus Perty 1849 are such problematic species. Although Lepocinclis ovum is recognized as a cosmopolitan and common species, and Lepocinclis globulus is the type species of the genus Lepocinclis, their correct identification is nearly impossible. The reason is that over 30 morphologically similar taxa appear in the literature, but no good diagnostic features exist to distinguish most of them. Fig. 1. a) original Ehrenberg's drawing of L. ovum, b) morphology of L. ovum, c) morphology of L. globulus. a b c The samples were collected during seven vegetation seasons (2012-2018) from 30 eutrophic water bodies in Poland. DNA was obtained from the cells (20-400) isolated with a micropipette. Morphological and molecular features were studied for taxa isolated from the environment and for two strains from algae collections. Phylogenetic analyses were conducted on 54 sequences of nSSU rDNA which were used to calculate maximum likelihood and Bayesian trees. Fig. 2. Map illustrating sampling locations in Poland. This work was supported by the OPUS 2016/23/B/NZ8/00919 grant from the National Science Centre, Poland. Łukomska-Kowalczyk, M., Chaber, K., Fells, A., Milanowski, R. &amp; Zakryś, B. 2019. Molecular and morphological delimitation of species in the group of Lepocinclis ovum-like taxa (Euglenida). J. Phycol. 56:283-99. Zakryś, B., Łukomska-Kowalczyk, M., Chaber, K. Fells, A., 2020. Typification of Lepocinclis ovum (Ehrenberg) Lemmermann (Euglenophyta), a widespread freshwater species. Notulae Algarum No. 144.