This article explains how the use of the four plastid regions were used on the molecular level to display the phylogeny of Tricalysia and relations to similar genera. Also how the Genus Empogona has diverged from being a subgenus of Tricalysia and into a genus of its own. Tricalysia is the largest genera of tribe Rubiaceae, found in continental Africa. The four plastid regions used were: (trnL-F intron and spacer, rpL16 intron, accD-psal spacer, and Pet-D) From the plastid regions used all were low in genetic variability between the groups that were used in the study with the exception of the accD-psal spacer was high in genetic varability that is AT-rich, (highly repetitive). Both Genus Tricalysia and Genus Empogona “share a 250 base pair deletion in the accD-psal region.”
Tosh, James, Aaron P. Davis, and Steven Dessein. “Phylogeny of Tricalysia (Rubiaceae) and its Relationships w/ Allied Genera Based on Plastid DNA Data: Resurrection of the Genus Empogona.” Annals of the Missouri Botanical Garden 96.1 Mar. (2009): 194-213.