Phylogeny and generic limits in the sister tribes Psychotrieae and Palicoureeae (Rubiaceae): Evolution of schizocarps in Psychotria and origins of bacterial leaf nodules of the Malagasy species

Sylvain G Razafimandimbison; Charlotte M Taylor; Niklas Wikström; Thierry Pailler; Anbar Khodabandeh; Birgitta Bremer

doi:10.3732/ajb.1400076

Phylogeny and generic limits in the sister tribes Psychotrieae and Palicoureeae (Rubiaceae): Evolution of schizocarps in Psychotria and origins of bacterial leaf nodules of the Malagasy species

Am J Bot. 2014 Jul;101(7):1102-1126. doi: 10.3732/ajb.1400076. Epub 2014 Jul 20.

Authors

Sylvain G Razafimandimbison¹, Charlotte M Taylor², Niklas Wikström¹, Thierry Pailler³, Anbar Khodabandeh¹, Birgitta Bremer¹

Affiliations

¹ The Bergius Foundation at The Royal Swedish Academy of Sciences and Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
² Missouri Botanical Garden, P. O. Box 299, St. Louis, Missouri 63166-0299 USA.
³ UMR C53, Peuplements végétaux et Bioagresseurs en milieu tropical, Faculté des Sciences et Technologies, Université de La Réunion, 15 Avenue Réné Cassin, BP 7151 97715 Saint-Denis Cedex 9, La Réunion, France.

PMID: 25049266
DOI: 10.3732/ajb.1400076

Abstract

• Premise of the study: The pantropical, species-rich Psychotrieae and Palicoureeae are sister tribes of mostly drupe-bearing and nonbacterial leaf-nodulating species with problematic generic limits. This problem is more complicated in Psychotrieae due to the paraphyly of the genus Psychotria, the lack of diagnostic characters for some major lineages, and the poor sampling from some biodiversity hotspots. Schizocarps and bacterial leaf nodules have been used for recognizing formal groups in Psychotrieae, but their evolution and taxonomic value have not been studied using a robust phylogeny of the tribe.• Methods: We analyzed 287 samples from the entire ranges of the tribes, with particular emphasis on the Western Indian Ocean region, with the Bayesian Markov chain Monte Carlo method.• Key results: All allied Psychotria genera investigated are nested within a paraphyletic Psychotria. Schizocarps evolved independently two times within Psychotria, and one reversal back to the drupaceous condition is inferred. The Malagasy leaf-nodulated Psychotrieae (except Apomuria bullata) and the Comorian non-leaf-nodulated Psychotria conocarpa are nested within the (African) leaf-nodulated clade. Within Palicoureeae, Chassalia is paraphyletic with respect to Geophila sensu stricto, and the Malagasy Geophila gerrardii and the African Hymenocoleus are closely related.• Conclusions: A widely circumscribed Psychotria encompassing the entire Psychotrieae is supported. Within Psychotria, two separate origins of schizocarps from drupes, one reversal back to the drupaceous condition, and two independent origins of the Malagasy leaf-nodulated species are inferred. A new genus Puffia is described to accommodate Geophila gerrardii, and a narrow circumscription of Chassalia is adopted. Thirty-two new combinations, two lectotypifications, and 25 new names are presented.

Keywords: Madagascar; Psychotrieae alliance; Rubiaceae; Western Indian Ocean region; bacterial nodules; schizocarp; systematics; taxonomy.