DNA barcoding and molecular phylogeny indicate that three members of the "morning glory" (Ipomoea nil species complex) are conspecific

The Ipomoea nil species complex, commonly known as "morning glories", are common and economically important weeds throughout the world. However, their confusing taxonomy can limit their further utilization and management. Here, DNA barcoding analyses were performed based on ITS and rbcL regions of 64 samples, covering almost all morphological variants of this species complex, to test whether the named species can be distinguished from each other. Multiple phylogenetic analyses, including parsimony, maximum likelihood and Bayesian inference were also carried out to assess their relationships. Our results showed that none of the nominal species can be successfully identified because none of them are exclusive lineages. We propose that I. hederacea, I. nil and I. purpurea belong to a single biological species. In consideration of their diverse habitats and phenotypic plasticity, we suggest that I. hederacea, and I. purpurea should be at the best regarded as two ecotypes.