Complete plastid genomes have recently been proposed as ”super-barcodes” for genetic identification and delineation in plants, for which standard DNA barcodes may fail. However, relatively few studies have fully considered the genetic mechanisms inherent to the taxonomic complexity of specious genera and how this may affect species resolution via complete plastome barcodes. Pedicularis is a highly diversified group of plants whose floral traits have undergone rapid radiation in the Himalaya-Hengduan Mountains, which can complicate identification and classification within the group based on morphological traits alone. In this study, we analyzed 292 plastomes representing 96 species of Pedicularis to compare species discrimination rates with those based on standard DNA barcodes. The results show that the traditional standard barcode (nrITS+matK+rbcL+trnH-psbA) and the large single copy (LSC) region of the plastid genome share the highest discrimination rates (80.21%), followed by the plastid genome, the supermatrixes of protein-coding genes and high variable regions (79.17%), and the matK gene and ycf1 gene alone could discriminate 78.13% of species. Further, we found that the sequence length and percentage of parsimony-informative sites significantly influence species discrimination rates, and genes with higher species discrimination rates are more likely to be conservative in selection. Given the extra costs and time required for generating such “super-barcodes” to try to discern species in taxonomically complex genera, this study questions their use and calls for more efforts to explore nuclear markers that may improve discrimination rates in future studies with relatively low-cost and effort.

We aimed to infer the phylogenetic relationships of populations of Lobelia columnaris using chloroplast genomes and estimate the divergence time to reconstruct its historical colonization on the sky islands of Bioko and Cameroon. Specifically, we aim to answer the following questions: (1) What is the phylogenetic relationship among Bioko Island and Cameroon populations? (2) Are the older populations found on the older sky islands? (3) Does the colonization history reflect the age of the sky islands? We assembled novel plastomes from 20 individuals of L. columnaris from five mountain systems. The plastome data was explored with phylogenetic analyses using Maximum likelihood and Bayesian Inference. The complete plastome size varied from 164,609 bp to 165,368 bp. The populations of L. columnaris have a monophyletic origin, subdivided into three plastome-geographic clades. The plastid phylogenomic results and age of the sky islands indicate that L. columnaris colonized first along the Cameroon Volcanic Line’s young sky islands. The earliest divergent event (1.54 Ma) split the population in South Bioko from those on the mainland and North Bioko. The population of South Bioko was likely isolated during cold and dry conditions in forest refugia. Presumably, the colonization history occurred during the middle-late Pleistocene from South Bioko’s young sky island to North Bioko and the northern old sky islands in Cameroon. Furthermore, the central depression with lowland forest between North and South Bioko is a current geographic barrier that keeps separate the populations of Bioko from each other and the mainland populations. The Pleistocene climatic oscillations led to the divergence of the Cameroon and Bioko populations into three clades. L. columnaris colonized the older sky island in mainland Cameroon after establishing South Bioko’s younger sky islands. The biogeography history was an inverse progression concerning the age of the Afromontane sky islands.