Comparison of ITS versus COI DNA barcodes in species–level identification.

Panel A and B refer to ITS and COI respectively. Dark grey shading indicates intraspecific distances whereas light grey interspecific distances. Y axis shows percentage of named species and genera that fall into pairwise distance categories (X-axis). Both A and B share same X-axis. Although both ITS and CO1 barcodes fall within the 0–0.02% range, note how ITS has a sizeable gap in genetic distance within species compared to between species, that is lacking for COI marker. In this study 2% or less PWD between strains was used as a species cut off, which encompassed 94% of strains. Abbreviations: Sym: Symbiodinium and Sym gp. A? refers to unknown group A Symbiodinium sp.; Karl.: Karlodinium; K. ven.: Karlodinium veneficum; C.sp.: Cryptoperidiniopsis sp.; Scr.: Scrippsiella; S.troch.: Scrippsiella trochoidea.