Psychotria, BREMEKAMP, 1934

Taylor, Charlotte M., 2020, Overview of Psychotria in Madagascar (Rubiaceae, Psychotrieae), and of Bremekamp’s foundational study of this group, Candollea 75 (1), pp. 51-70 : 54-55

Psychotria

Morphology and identity of Bremekamp’s Malagasy Psychotria BREMEKAMP (1934, 1961 , 1963) circumscribed Psychotria based primarily on pyrene characters, along with some other features he did not explicitly list. He diagnosed Psychotria ( BREMEKAMP, 1934, 1963) by its pyrenes that adaxially have a flat face with two shallow longitudinal grooves that lie on each side of a medial ridge (Bremekamp described this diagnostic pyrene form as a shallow longitudinal excavation divided in two by a medial ridge, but as noted by PIESSCHAERT (2001: 327 –328), most taxonomists see the alternative condition, a plane face with two longitudinal furrows). Bremekamp’s Psychotria ( BREMEKAMP, 1934, 1961, 1963) was also diagnosed, in practice, by a lack of the features that diagnosed his other genera, i.e., consistently deciduous stipules ( Mapouria ), pseudoaxillary or axillary inflorescences ( Notopleura (Benth.) Bremek. , Ronabea Aubl. ), capitate inflorescences with each flower involucrate ( Cephaelis Sw. ), multilocular ovaries ( Psathura , Nonatelia Aubl. ), dehiscent fruits ( Cremocarpon , Pyragra ), and pyrenes that are flat on the adaxial face ( Mapouria , Gamotopea Bremek. ). Bremekamp’s diagnosis of Psychotria is problematic, however, because his diagnostic pyrene characters have been shown to vary without any apparent systematic pattern and there is no other feature that diagnoses his group by its presence (i.e., no apomorphy).

PETIT (1964) and PIESSCHAERT (2001) surveyed Psychotria pyrenes in Africa and world-wide, respectively, and found continuous variation in the form of the pyrenes’ adaxial walls, and no correlation of pyrene form with any other characters or systematic groupings. Additionally, Bremekamp’s characterization here is partially inaccurate, because the form of the adaxial pyrene wall varies within some species and even in different fruits of a single plant. Bremekamp’s diagnostic feature for Psychotria is, thus, not diagnostic, and the species grouped in Psychotria by BREMEKAMP (1963) are heterogenous morphologically and difficult to characterize as a group. The only features that seem to be consistent within Bremekamp’s Malagasy Psychotria are not unique to it: the mature fruits are blue or white, and PIESSCHAERT (2001) found all the

[A: Antilahimena 6104; B: Razanatsima et al. 1660; C: Ratovoson 1707] [Photos: A: P. Antilahimena; B: A. Razanatsima; C: F. Ratovoson]

species included here have pyrenes that lack PGS’s and have an alchohol-soluble red pigment. The characterization of a genus by its lack of the diagnostic features of other groups results in a classification that with genera variously diagnosed by shared derived features (synapomorphies) and genera that are residual, paraphyletic assemblages that have the ancestral features of the group. This was a common approach to classification in Bremekamp’s time, but it is not in accordance with most current plant taxonomy. Modern systematic approaches to classification emphasize the consistent separation of groups that comprise entire lineages and have shared derived features ( RAZAFIMANDIMBISON et al., 2014). BREMEKAMP (1963) recognized seven informal species groups in Psychotria based on leaf size and form, stipule form, drying color of the specimens, inflorescence form, and the presence of bacterial nodules. He designated these groups informally with numbers, and called each a “Group” in his key but a “Taxon” in his species treatment.

Bremekamp’s Malagasy Psychotria analyzed with molecular data ANDERSSON (2002) did not study any Malagasy or Comoran species classified by BREMEKAMP (1963) in Psychotria . RAZAFIMANDIMBISON et al. (2014) ’s molecular analysis included 13 species from this region that BREMEKAMP (1963) classified in Psychotria , and found these placed on two clades. The species here without bacterial nodules were grouped with species of Bremekamp’s Mapouria , Apomuria , and Psathura .The species with bacterial nodules were grouped with other species of Apomuria and some nodulated African species; here the Malagasy species were grouped on one subclade, and separated from the Comoran species. RAZAFIMANDIMBISON et al. (2014) concluded that Psychotria as circumscribed by Bremekamp in Africa and the western part of the Indian Ocean was paraphyletic without the inclusion of Apomuria , Cremocarpon , Mapouria , Psathura , Pyragra , and Trigonopyren . The extensive morphological heterogeneity of Bremekamp’s Psychotria is mirrored by the extensive polyphyly they found in this group. In the results of RAZAFIMANDIMBISON et al. (2014), all of Bremekamp’s Malagasy Psychotria species groups are paraphyletic.