Genetic Relationships and Ancestral Character State Reconstructions of Psychotria L. Sect. Straussia (a. Gray) Fosberg (Rubiaceae).

Abstract

Taxonomic classifications based on morphology and molecular studies of members in Psychotria sect. Straussia have been problematic leaving a number of species identities’ in doubt. Also, previous phylogenetic studies showed that Psychotria hawaiiensis may represents multiple taxa currently circumscribed under a single species. To resolve the identity of the taxa currently included in this species two nuclear and two chloroplast markers were used and analyzed using Maximum Likelihood and Bayesian Inference. Additionally, two morphological characters were examined in BayesTraits to elucidate relationships among taxa. The molecular analyses reveal that P. hawaiiensis is polyphyletic and varieties hillebrandii and scoriacea are not closely related to variety hawaiiensis and they may represent distinct species. Variation in domatia size and leaf venation are consistent with this interpretation of P. hawaiiensis and its lack of monophyly, but future work should investigate their taxonomic value within this sect. Straussia. Nomenclatural changes that may be needed in the future include reducing P. hawaiiensis var. hawaiiensis to varietal rank of P. mariniana. In addition, recognizing P. hawaiiensis var. hillebrandii and var. scoriacea as separate distinct species. Also, many of the recognized taxa are not well differentiated suggesting that other methods such as next-generation sequencing (NGS) technique should be pursed to disentangle the relationships of these taxa.