Croton guianensis Aublet (1775: 882)

Burilli, Nicolas Giovanny, Pereira, Amanda Da Paixão Noronha & Caruzo, Maria Beatriz Rossi, 2025, Synopsis of Croton section Barhamia subsection Barhamia (Euphorbiaceae), Phytotaxa 705 (2), pp. 162-172 : 165-166

8. Croton guianensis Aublet (1775: 882) .— Croton subluteus Lamarck (1786: 210) , nom. illeg.— Oxydectes guianensis (Aublet) Kuntze (1891: 611) . Type:—FRENCH GUYANA. Cayenne, s.dat., J.B.C.F. Aublet s.n. (lectotype designated here, BM 015177111!; isolectotypes, W 0356899! [photo F 32528!], S-R-10522!).

Croton tafelbergicus Croizat (1948: 401) . Type:— SURINAME. Sipaliwini: Tafelberg, south of East Ridge , 900 m altitude, 1 September 1944, B. Maguire 24582 (holotype, A 00047445!; isotypes, K 000254412!, NY 00262963!, U 0145910!, US 00109771!).

Croton guianensis is a shrubby to arborescent species, found in Brazil (Roraima, Amapá), French Guyana, Guyana, Suriname, and Venezuela. It occurs from 80 to 710 m elevation in the Amazon domain, typically on sandstone and moist soil.

Notes:— In accordance with Article 9.12 of International Code of Nomenclature (Turland et al. 2018), the designation of a lectotype is required. We have selected the specimen BM 015177111, as it is the one that most accurately represents the species morphologically and given that it is housed in the herbarium where Aublet’s original collection is deposited. This specimen was used for both original species description and its illustration.

Although section Barhamia is characterized by the absence of glands at the acropetiolar region ( van Ee et al. 2011), Croton guianensis has stipitate glands at the base of the leaves, a feature clearly visible in the original illustration and cited in the protologue of the species. Due to the presence of this characteristic, we could have chosen to exclude the species from the group. However, one of the phylogenetic studies with molecular data carried out with the genus Croton has sampled a specimen of C. guianensis, Berry 5535 (MICH 1544158, MO 1370537; accession numbers AY971215 , AY971303 , respectively), and the species emerged among others from section Barhamia ( Berry et al. 2005) . Furthermore, the species share morphological characteristics with members of the section Barhamia (e. g. stellate indumentum, serrate margins, pinnate venation, glandular stipules, terminal and bisexual inflorescences, sepals of pistillate flowers glandular, and tetrafid styles). Therefore, we decide provisionally to maintain this species in the section until further studies are carried out on the systematics and evolutionary history of the group.

Representative specimens:— GUYANA. Dadanawa: Rupununi, 2º49’N, 59º 31’W, 6 June 1995, M.J. Jansen- Jacobs, B.J.H. ter Welle, C. Gustafsson & V.James 3947 (K 004622729!, MBM 223992!, MO 1370533!, NY 03979189!, US 00602113!).