Eumachia DC., Prodr.

Taylor, Charlotte M., Razafimandimbison, Sylvain G., Barrabé, Laure, Jardim, Jomar G. & Barbosa, Maria Regina V., 2017, Eumachia expanded, a pantropical genus distinct from Psychotria (Rubiaceae, Palicoureeae), Candollea 72 (2), pp. 289-318 : 292-294

Eumachia DC., Prodr. 4: 478. 1830.

Ξ Psychotria sect. Eumachia A.C. Sm. in Bernice P. Bishop Mus. Bull. 141: 151. 1936 .

Typus: Eumachia carnea (G. Forst.) DC.

= Margaris Griseb., Cat. Pl. Cub. 134. 1866 [nom. illeg.] [not Margaris DC. ]. Ξ Margaritopsis C. Wright in Sauvalle in Anales Acad. Ci. Med. Habana 6: 146. 1869 [nom. nov]. Typus: Margaritopsis acuifolia C. Wright Ξ Eumachia acuifolia (C. Wright) Delprete & J.H. Kirkbr .

= Mapouria ser. Chaenotrichae Müll. Arg. in Flora 59: 496. 1876. Lectotypus (designated here): Mapouria chaenotricha (DC.) Müll. Arg. Ξ Eumachia chaenotricha (DC.) Razafim. & C.M. Taylor , syn. nov .

= Readea Gillespie in Bernice P. Bishop Mus. Bull. 74: 35. 1930. Typus: Readea membranacea Gillespie Ξ Eumachia membranacea (Gillespie) Delprete & J.H. Kirkbr.

= Chytropsia Bremek. in Recueil Trav. Bot. Néerl. 31: 291. 1934. Ξ Psychotria sect. Chytropsia (Bremek.) Steyerm. in Mem. New York Bot. Gard. 23: 484. 1972. Typus: Chytropsia astrellantha (Wernham) Bremek. Ξ Eumachia astrellantha (Wernham) Delprete & J.H. Kirkbr.

= Chazaliella E.M.A. Petit & Verdc. in Kew Bull. 30: 268. 1975. Typus: Chazaliella abrupta (Hiern) E.M.A. Petit & Verdc. Ξ Eumachia abrupta (Hiern) Delprete & J.H. Kirkbr.

Eumachia includes 83 species of shrubs and small trees found in seasonal to wet vegetation at low to middle elevations in most tropical regions ( Fig. 1 ; BARRABÉ et al., 2012: fig. 4). Eumachia is found widely in tropical continental Africa (20 species), the American tropics (27 species), southeast Asia, northeastern Australia, New Guinea, and numerous Pacific Islands (36 species). Eumachia apparently is absent in Madagascar and the Indian subcontinent ( RAZAFIMANDIMBISON et al., 2014). The number of species of Eumachia in Asia, New Guinea, and the Pacific region is higher than previously estimated, and moves the center of diversity of the genus to this region.

Eumachia is characterized by raphides in its tissues; a woody habit, as a shrub or sometimes small tree; a characteristic yellowish green drying color of the vegetative structures and inflorescence axes; opposite leaves; stipules that are interpetiolar or sometimes united around the stem, at least partially persistent, and often bear a caducous gland on the tip of each segment; terminal inflorescences that are basically cymose with the axes and bracts green to whitened; four- or five-merous flowers that are generally distylous; salverform to funnelform, white to cream or yellowish green corollas with valvate aestivation and usually barbate throats; bilocular ovaries with the ovules solitary and basal in each locule; drupaceous, ellipsoid to subglobose, orange to red fruits; pyrenes that are smooth to ribbed abaxially, plane to concave adaxially (i.e., without a longitudinal groove), and have hard walls that lack the ethanol-soluble pigment found in Psychotria and marginal PGS’s ( PIESSCHAERT, 2001); and seeds with the endosperm entire (i.e., not ruminate). The stipules vary morphologically among the species but all have a characteristic Eumachia form: they either become hard and yellowed to ocher with age and then slowly break off in fragments, or their top portion is deciduous and their basal portion persistent. The non-ruminate endosperm sometimes has a single T-shaped adaxial intrusion ( PIESSCHAERT, 2001). Most of these features are general characters of the tribe Palicoureeae , and thus as noted by ANDERSSON (2001) Eumachia is not easy to diagnose morphologically. Dried specimens are generally recognizable by the combination of their yellowish green color, yellowed to ocher fragmented stipules, terminal inflorescences, small to medium-sized white flowers with usually barbate corolla throats, orange to red drupaceous fruits, and raphides in the tissues.

Several morphological features vary widely in Eumachia , and significantly more variation is found among the Pacific species than in other regions. The stipules range in all regions from triangular to bilobed on each interpetiolar side, and in a few species they are initially entire and later split longitudinally to become bilobed; additionally some Pacific species have stipules that are fused into a tube with two short apical lobes [e.g., E. archboldiana (Fosberg) Barrabé et al. ]. Most Eumachia species have somewhat flattened stems with a medial longitudinal ridge on each interpetiolar side ( TAYLOR, 2005: 174, Fig. 1 ), but some have rounded smooth internodes. Species that grow in seasonal vegetation in all regions often develop corky stems. The inflorescences of Eumachia show similar variation to many other Rubiaceae genera, with the arrangement basically dichasially cymose and ranging from lax [e.g., E. cymuligera (Müll. Arg.) Razafim. & C.M. Taylor, E. leptothyrsa (Miq.) Barrabé et al. ] to short or contracted into a subcapitate head [e.g., E. cephalantha (Müll. Arg.) Delprete & J.H. Kirkbr. , E. kappleri (Miq.) Delprete & J.H. Kirkbr. ]. The corollas range from 2 mm long to around 2 cm long. As documented by BARRABÉ et al. (2012), the pyrenes of all the species have PGS’s located on their margins, and some species additionally have abaxial PGS’s. A few specimens show all of the characters of Eumachia except they dry blackened rather than yellowish green; similar variation in drying color is found in some other genera of Rubiaceae (e.g., Palicourea Aubl. ).

The pollen of Eumachia has been documented for only a few species, and is variously aperturate or inaperturate. ANDERSSON (2001) initially reported the pollen of this genus to be aperturate based on the species studied by him and by JOHANSSON (1992). JOHANSSON (1992) considered the aperturate pollen of the species of Eumachia that he studied to differ in form, and classified it variously in his type XII (2 spp.), type XVI (5 species), and type XIX (1 sp.). However BARRABÉ et al. (2012) found that Psychotria leptothyrsa Miq. also belongs to Eumachia , and JOHANSSON documented the pollen of this species as inaperturate and included it in his type XX. Two other species with inaperturate pollen have been suggested to be related to species of Eumachia , but these other species are not included in this genus here. One other species that JOHANSSON classified as having type XX pollen, Psychotria hunteri (Horne ex Baker) A.C. Sm. , was considered by SMITH & DARWIN (1988) to be related to Eumachia carnea but more recent study (BARRABÉ, pers. obs.) finds that this species is related instead to a Fijian group of Psychotria . Inaperturate pollen of JOHANSSON’S type XXI was documented in another species that Steyermark included in the Chytropsia group, Psychotria spiciflora Standl. , but that species belongs to Palicourea ( TAYLOR, 2015) .

Fig. 1. – Photographs of Eumachia DC. A, B. Eumachia lyciiflora (Baill.) Barrabé, C.M. Taylor & Razafim. ; C. Eumachia microdon (DC.) Delprete & J.H. Kirkbr. ; D. Eumachia boliviana (Standl.) Delprete & J.H. Kirkbr. ; E, F. Eumachia depauperata (Müll. Arg.) M.R. Barbosa & M.S. Pereira ; G. Eumachia oleoides (Baill.) Barrabé, C.M. Taylor & Razafim.

[A: Barrabé & Barriole 747; B: Barrabé 589; C: Coronado 6251; D: Araujo 1247; E-G: Unvouchered photos] [Photos: A, B: L. Barrabé; C: O.M. Montiel; D: C. Davidson; E, F: J. Jardim; G: H. Vandrot]

Study of the secondary chemistry of the tribes Psychotrieae and Palicoureeae is just beginning (MARTINS & NUNEZ, 2015), but BERGER (2012) surveyed several species of Palicoureeae . He suggested for the first time that some chemical constituents, in particular cyclotryptamine alkaloids, may be another characteristic of Eumachia that distinguishes it from other genera of Palicoureeae , which appear to lack these compounds. His study was complicated by limited species sampling and lack of clarification as to which Psychotria species should be classified in Eumachia , particularly among the Pacific species where more chemical variation was found, so further study will be needed to confirm this.

A synoptic treatment of the African species of Eumachia , including a key and nomenclatural synonymy, was presented by VERDCOURT (1977; as Chazaliella ). A comparable synoptic treatment of the Neotropical species was presented by TAYLOR (2005; as Margaritopsis ). The Asian, Australian, New Guinean, and Pacific species of Eumachia have never been treated together before now. Lectotypifications for several Neotropical names were made by DELPRETE & KIRKBRIDE (2015).

Most of the 12 species included in Mapouria ser. Chaenotrichae ( MÜLLER, 1881: 416-422) have been more recently classified in Margaritopsis ( TAYLOR, 2005; some of them as synonymous names). No types were designated by MÜLLER (1876, 1881) for his infrageneric groups. Based on the general characterization of Mapouria ser. Chaenotrichae and the name Müller gave it, M. chaenotricha is here designated as the lectotype for this series. Two species originally classified in this series, M. riedeliana Müll. Arg. and M. mandiocana Müll. Arg. , belong to Psychotria ; nine of the original species belong to Eumachia ; and the identity of the remaining name, Mapouria vestita (Presl) Müll. Arg. , is not yet clear.

Figures

Fig. 1. – Photographs of Eumachia DC. A, B. Eumachia lyciiflora (Baill.) Barrabé, C.M. Taylor & Razafim.; C. Eumachia microdon (DC.) Delprete & J.H. Kirkbr.; D. Eumachia boliviana (Standl.) Delprete & J.H. Kirkbr.; E, F. Eumachia depauperata (Müll. Arg.) M.R. Barbosa & M.S. Pereira; G. Eumachia oleoides (Baill.) Barrabé, C.M. Taylor & Razafim. [A: Barrabé & Barriole 747; B: Barrabé 589; C: Coronado 6251; D: Araujo 1247; E-G: Unvouchered photos] [Photos: A, B: L. Barrabé; C: O.M. Montiel; D: C. Davidson; E, F: J. Jardim; G: H. Vandrot]