Trigonopyren

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 : 60

Trigonopyren

Bremekamp’s Trigonopyren

BREMEKAMP (1963) also separated Trigonopyren based on pyrene and endosperm characters, and his circumscription and characterization of this genus are also problematic morphologically. He diagnosed this genus by endosperm without ruminations or furrows, and pyrenes that are trigonous in crosssection and have smooth thin-textured walls ( Fig. 4K–P ). Bremekamp included here eight species from Madagascar and one from the Comores that share a set of additional features: costate internodes ( Fig. 4K–M ), a distinctive stipule form and dehiscence scar ( Fig. 4K–M ), pedunculate cymose inflorescences, four- or five-merous flowers, and a generally green or grayish green drying color. He also diagnosed Trigonopyren by its apparently monomorphic (i.e., not distylous) flowers with the stigmas exserted and the anthers partially exserted. These species are morphologically recognizable as a group, but his diagnostic characters are not unique in Psychotria and some of them vary within this group. As noted above, the presence and pattern of endosperm rumination is variable across Psychotria without evident systematic pattern. Trigonous smooth pyrenes are found as occasional developmental variants in Psychotria species with abaxially rounded pyrenes, so this form is not unique to this group, and the pyrenes of the Trigonopyren species actually vary from this form to abaxially rounded and adaxially furrowed and ridged. The walls of Trigonopyren ’s pyrenes are distinctive in being relatively thin, but similarly thin pyrene walls are found widely in Psychotria in Madagascar and elsewhere. The other characters BREMEKAMP (1963) used to characterize Trigonopyren , the unusual stipules and floral biology, are not unique either in Psychotria plus his descriptions were not completely accurate. The stipule form of Trigonopyren is distinctive, but is also found in some species of Bremekamp’s Psychotria (e.g., P. perrieri Bremek. ). Monomorphic flowers are found in occasional species of Psychotria , and at least some species of Trigonopyren are actually distylous. Trigonopyren was provisionally synonymized with Psychotria by SCHATZ (2001), but was recognized by other authors ( PIESSCHAERT, 2001; DAVIS et al., 2007).

Bremekamp’s Trigonopyren analyzed with molecular data

A N DE R S S ON (2 0 0 2) d i d n o t e v a l u a t e Tr igonopyren . RAZAFIMANDIMBISON et al. (2014) studied four samples of Trigonopyren , with three of them identified to species. Their analysis found these grouped together on a clade nested in Psychotria , and they synonymized Trigonopyren .

Figures

Fig. 4. – Some morphological features of Psychotria L. in Madagascar. A–B. Apomuria, Psychotria biloba (Bremek.) A.P. Davis & Govaerts: A. Fruiting branch; B. Cross-section of seed (removed from pyrene). C–D. Apomuria, Psychotria punctata Vatke: C. Fruit; D. Cross-section of seed. E. Psychotria kirkii Hiern, cross-section of seed. F–G. Psathura, Psychotria borbonica (J.F. Gmel.) Razafim. & B. Bremer: F. Fruit; G. Cross-section of fruit, with four pyrenes. H–I. Psathura, Psychotria batopedina (Verdc.) Razafim. & B. Bremer: H. Fruit; I. Cross-section of fruit, with five pyrenes. J. Unusual stipules in Malagasy Psychotria L. (TAYLOR, in press). K–N. Trigonopyren, Psychotria tsiandroi Razafim. & B. Bremer.: K. Node near stem apex with developed stipule, unbroken and with glandular projections; L. Node below the node shown in K, with aging stipule that is falling off in fragments; M. Node in lower part of stem, with old stipule that has fallen off except for persistent basal part of sheath; N. Cross-section of pyrene. O–P. Trigonopyren, Psychotria bealanensis Razafim. & B. Bremer: O. Fruit; P. Cross-section of fruit, with two pyrenes.