Microalgae have been increasingly studied for the application in human and animal food, in the production of biodiesel, pigments, drugs, among others. For the safe application and standardization of compounds obtained from microalgae, and from large-scale crops, or even for marketing permission in some countries, correct identification of microorganisms is essential (Borowitzka et al., 2016).However, the classification of microalgae has recently undergone modifications, so that ancient and artificial classification systems are being replaced by a new and more natural classification system, the phylogenetic system. Currently, the systematics of levels such as families and genera are considered provisional, since detailed molecular sampling is necessary for the correct positioning and identification of the coccoid microalgae taxa (Krienitz et Bock, 2012).Some major groups of planktonic green algae have recently been studied by molecular methods, having their phylogeny and identification passed by re-elaborations (e.g. Bock et al., 2010, Huss et al., 1999, Garcia et al., 2017). An economically important genus for feeding is Chlorella, for which simple cellular forms underestimate genetic diversity, whose "green ball" shape, seen in several phylogenetic independent lineages of this species, corresponds to different genera and species, defined by molecular biology (Huss et al., 1999, Neustupa et al., 2009). The analysis of the 18S and ITS-1 and -2 rDNA markers of the Chlorellaceae family (Luo et al., 2010) differentiated six genera within the Chlorella clade, revealing that several morphological criteria are phenotypic characteristics, representing adaptive responses to environmental factors. Therefore, morphologically similar lineages may be very different in molecular terms and distinct strains morphologically may be very similar in their molecular biology.The systematics and delimitation of species in protists, where microalgae are inserted, have recently been discussed in many publications and still present controversial issues (Ryaánek et al., 2015), with the circumscription of the species and the speciation pattern of these organisms among the central topics of this discussion (Malavasi et al., 2016). The knowledge accumulated so far suggests that both the morphological concept and the biological concept of species can not solve the central issues of the natural grouping of green microalgae (Krienitz et Bock 2012), and the phylogenetic concept of species is essential for the identification and systematics of microalgae. Despite the growing economic and ecological importance of microalgae, the problems related to their identification and the need for correct identification for higher quality in the biotechnological application of organisms, many studies still require robust taxonomic work.In this way, the creation of a vigorous taxonomic base obtained with traditional taxonomy and phylogenetic relationships, is an important step for the study of these microorganisms and for their application with safety and quality.
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