The monospecific genus Aitchisonia (Rubiaceae), a suffrutescent plant endemic to Afghanistan, Iran, and Pakistan, was merged in the genus Plocama of the monogeneric tribe Putorieae sensu Backlund et al. (Spermacoceae alliance, subfamily Rubioideae). This decision was based on the phylogenetic placement of the specimen Rafei and Zangooei 25651 (FUMH) erroneously identified as Aitchisonia rosea in Plocama. This specimen was later correctly re-identified as Plocama dubia, rending the position of Plocama rosea (= Aitchisonia rosea) in Plocama (thus Putorieae) doubtful. We reconstructed a new phylogeny of Spermacoceae alliance based on trnL-F and nrITS sequence data and using the Bayesian method to: 1) assess the phylogenetic placement of P. rosea within Rubioideae, using new material from Iran; 2) pinpoint the phylogenetic positions of Plocama asperuliformis, P. crucianelloides, P. dezfulensis, P. ehrendorferi, P. kandaharensis, P. szowitsii, and P. vassilczenkoi; and 3) re-assess the monophyly of Plocama bruguieri and P. eriantha. The trnL-F and nrITS trees further support the monophyly of the Rubieae complex, but were not fully congruent. The trnL-F tree resolved Plocama rosea as sister to tribe Rubieae (including Kelloggia), while the nrITS tree was inconclusive. We described a new monogeneric tribe Aitchisonieae to accommodate P. rosea. Our nrITS analysis resolved Plocama crucianelloides in the Plocama Middle-Eastern clade and P. asperuliformis, P. dezfulensis, P. ehrendorferi, P. kandaharensis, P. szowitsii, and P. vassilczenkoi in the Plocama Central-Asian clade, both sensu Rincón-Barrado et al. The non-monophyly of P. bruguieri and P. eriantha is confirmed.
