Fig. 1 Diagram of morphological characteristics of Chlorellaceaen members. A, B, D, E and Q were from Krienitz et al (2015); I and L were from Bi & Hu (2004); M was from Hu et al (1980); J, K, L and P were from Liu & Hu (2012); C, F, G, H, N and O were drawn by the authors.

Fig. 2 Phylogenetic analysis of Chlorellaceae based on 18S rDNA was inferred using the neighbor-joining method in MEGA7, with 1,000 replicates of bootstrap test. If there was a corresponding Chinese name in the Latin name, see Table 1 and Appendix 1. The tree was drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The analysis involved 115 nucleotide sequences. All ambiguous positions were removed for each sequence pair. There was a total of 1,679 positions in the final dataset.

Fig. 3 Phylogenetic tree of the Chlorella clade based on 18S rDNA + ITS sequences using maximum likelihood (ML) methods. The asterisk refers to the authentic strains. If there was a corresponding Chinese name in the Latin name, see Table 1 and Appendix 1. The analysis involved 155 nucleotide sequences. There was a total of 2,253 positions in the final dataset. The best substitution model of each partition was estimated using default parameters of IQ-TREE web server (Trifinopoulos et al, 2016). Phylogenetic tree was reconstructed on the IQ-TREE web server. Values at the branches represent SH-aLRT support (%), aBayes support, ultrafast bootstrap support (%), respectively.

Fig. 4 Phylogenetic tree of Parachlorella clade based on 18S rDNA + ITS sequences using maximum likelihood (ML) methods. If there was a corresponding Chinese name in the Latin name, see Table 1 and Appendix 1. The analysis involved 97 nucleotide sequences. There was a total of 2,217 positions in the final dataset. The best substitution model of each partition was estimated using default parameters of IQ-TREE (Trifinopoulos et al, 2016). Phylogenetic tree was reconstructed on the IQ-TREE. Values at the branches represent SH-aLRT support (%), aBayes support,.ultrafast bootstrap support (%), respectively.

Fig. 5 Phylogenetic tree of Chlorellaceaen species based on the sequences of 72 plastid proteins. If there was a corresponding Chinese name in the Latin name, see Table 1 and Appendix 1. The amino acid sequences of each of 72 proteins were individually aligned, trimmed, concatenated and model selected using PhyloSuite v1.2.2 (Zhang et al, 2020). There was a total of 16,872 positions in the final dataset. Phylogenetic tree was reconstructed on the IQ-TREE (Trifinopoulos et al, 2016). Values at the branches represent SH-aLRT support (%), aBayes support, ultrafast bootstrap support (%), respectively.

Fig. 6 Phylogenetic tree of Chlorellaceaen species based on the sequences of 32 mitochondrial proteins. The amino acid sequences of each of 32 proteins were individually aligned, trimmed, concatenated and model selected using PhyloSuite v1.2.2 (Zhang et al, 2020). There was a total of 7,665 positions in the final dataset. Phylogenetic tree was reconstructed on the IQ-TREE (Trifinopoulos et al, 2016). Values at the branches represent SH-aLRT support (%), aBayes support, ultrafast bootstrap support (%), respectively.