Study on the Population Genetics of Indigofera decora Complex Based on cpDNA and nrDNA ITS Sequences

To address questions of interspecific genetic variability and explore the mechanism of speciation in the Indigofera decora complex, a phylogenetic analysis of the complex distributed in eastern and neighboring regions of China was conducted based on cpDNA (ndhJ-trnF and trnD-trnT) and nrDNA (ITS) sequences, including 185 individuals from 24 populations.Results suggested that the Indigofera decora complex had high haplotype diversity and low genetic diversity (cpDNA: H_d=0.778,π=0.00123; ITS: H_d=0.909,π=0.01290).Anhui and Zhejiang were suggested to be the centers of genetic diversity based on the population diversity index.Most genetic variation in the complex was confined to among-population differentiation rather than within-population variation.Intraspecific differentiation among populations was high (cpDNA: F_ST=0.848; ITS: F_ST=0.787), while gene flow was low (cpDNA: Nm=0.228; ITS: Nm=0.241), which showed that isolation-by-distance (genetic shift) or habitat fragmentation promoted species diversification of the complex.Incomplete reproduction isolation of the species resulted in shared haplotypes among species by introgression.The populations of I.kirilowii were diverged from other populations and had no shared haplotypes with other species, thus its taxonomic status should be kept.However, further study is needed on the taxonomic status of other species of the complex.