3.2 Phylogenetic relationships based on mitogenome sequences
In the phylogenetic trees constructed based on mitogenome sequences, four distinct lineages were represented among diploids (Figure 2a). They followed a pattern of geographical origin for the native samples, with the invasive individuals from Tibet belonging to two of the lineages. The first lineage (A) mainly contained 24 invasive individuals and source individuals from the lower Yangzte River (TH and CL) and Huai River (RR and HZL). The single individual from SC and one individual from DQ also belonged to lineage A. The second lineage (B) was composed of the remaining seven invasive individuals and source individuals from the mid Yangzte River (SS and ZDL). The third lineage (C) contained eight native individuals from the Songhua River (DQ and JPL), and the single individual from Fujian separately formed the fourth lineage (D).
For triploids, four lineages E, F, G and H were observed with 59, 15, 3 and 1 individuals being included, respectively (Figure 2b). However, the phylogenetic pattern of triploids was not related to geographical origin, with each large lineage containing individuals from different river systems and including invasive individuals. By combining diploids and triploids together, four lineages were found with A, B, E and H being clustered into one super lineage, C and F into another big lineage, D and G into single lineages (Figure S2). Hence, the phylogenetic pattern was not associated with the ploidy level.