Hexaploid sweetpotato (Ipomoea batatas (L.) Lam.) may not be a true type to either auto- or allopolyploid
Fig 7
The most-parsimonious species tree embodying the two hybridization networks.
The gray-shaded outline represents the most parsimonious species tree that could be reconciled with the two hybridization networks. The two hybridization networks minus their outgroups were fitted in the gray-shaded species tree trunks, having matching partition-color-coded splits, numbered nodes and hybridization events (H1 to H4 in blue) as those in the two redrawn color-coded hybridization networks minus their outgroups at the bottom left and right for comparison. The three pairs of sweetpotato COSII lineages fitted in the species tree and their corresponding taxa in the two hybridization networks were labeled as br, bt, bl and b4 for trifida-like, tenuissima-like, littoralis-like and sweetpotato-specific COSII lineages, respectively, in black (first network) and green (second network) color circles. The reference COSII lineages in the three sweetpotato relatives and their corresponding taxa in the two hybridization networks were labeled as tr or tk, t, and L for those from the two I. trifida lines, I. tenuissima, and I. littoralis, respectively, with subscripted number 1 or 2 indicating the first and second network in respective partition-color circles. The tree sections predicting ancestral species (diploid Ip-N1, -N2, -N3 and -N7, tetraploid Ip-Tn, -Lt and -Hb) to sweetpotato were delimited by dashed lines. The H1 and H4 hybridizations were modeled as intraspecific introgression (IS) in I. trifida. The br (IB_Itr/Itrk_C2) and b4 (IB_Hp4_C2) lineages (light-blue and pink colored, respectively) in the second network were modeled as outcomes of incomplete lineage sorting (ILS) in the tree. The dotted light-purple lines mark an additional predicted COSII lineage (btr) in sweetpotato and the trifida and tenuissima-like one (Ltr) in I. littoralis, which would have descended from an ancestral linage branched at the node N1/1’. The three color-gradient blocks underneath the subgenome designations were used to emphasize that only parts of these diploid subgenomes were differentiated as represented by the differentiated multi-gene COSII lineages.