Volume 11 NOVONNumber 22001Three New Infraspecific Taxa of Manihot (Euphorbiaceae) from the Brazilian Neotropics Antonio C. Allem Embrapa Recursos Geneticos e Biotecnologia, C.P. 02372, 70849-970 Brasilia, DF, BrasilA RSTRACT. Manihot caerulescens subsp. I(aeis, M.carthaginensis subsp. hahnii, and M. dichotomavar. undulata, all three assigned herein to sectionGlaziorianae, are described and illustrated. laoni-hot carthaginensis subsp. hahnii appears endemicto northern and northwestern portions of Minas(erais. Manihot dichotoma var. undulata and M.caerulescens subsp. laeris are endemic to Brazil'snortheastern semiarid phytogeographic regionknown as caatinga. A new combination is providedfor M1. glaziovii, which is submerged as a subspe-cies in the expanded circumscription of M. car-thaginensis. Key words: Brazil. Euphorbiaceae. Manihot. Neotropics. Recent taxonomic studies of the genus Manihotin Brazil have disclosed a number of new speciesand taxa (Allem. 1989a. 19891), 1999). In the lastmonograph (Rogers & Appan. 1973) 98 specieswere recognized. all confined to the New Worldl.The economic importance of the genus resides inthe root crop cassava (Manihot esculents Crantzsubsp. esculenta). a major staple for rural and in-digenous populations in much of the Neotropicsand Paleotropics. Rogers and Appan (1973) as-signed ca. 80 species to Brazil. Recent reassess-ment of the Brazilian species yielded a more rea-sonable estimate of 45 species (Allem. 2001).However, at least two more new species will jointhe Brazilian taxa in the near future. Manihot is adifficult genus on account of the extensive infra-specific vegetative and floral variation; this explainsthe high levels of inflation recorded for the genus(e.g.. Rogers & Appan (1973) recognized 98 spe-cies out of 170 published prior to 1973). Croizat(1943) was of the opinion that the sections createdby Pax (1910) were unworkable from a practicalstanldpoint. Likewise. many of the sections recog-nize(d by Rogers and Appan (1973) were consideredtoo artificial to serve any practical purpose by Al-len) (2001). Sixteen groups of related taxa were pro-posed, with 45 species; group VI in particular, theManihot esculenta group, has already been exten-sively studied using genetic markers, and the mo-lecular results have coincided with the pheneticclassification (a comprehensive review of this bib-liography appears in Allem, 2001). Some authors(e.g.. Second et al.. 1997) have noted the large dis-crepancies existing between Rogers and Appan's(1973) treatment and Allem's more cohesive ,delim-itations of species. I)uring preparation of a treatment on section G(a-ziorianae Pax emend. Rogers & Appan. a grouplargely confined to caatinga vegetation in north-eastern Brazil, it was necessary to describe threenew taxa to document infraspecific variation: Ma-nihot caerulescens subsp. laeris. M. carthaginensissubsp. hahnii, and M. dichotoma var. undulata. Inaddition, because the names M. carthaginensis and11. glaziorii represent the same variable and wide-spread taxon within Manihot, a new combinationand status are provided for the latter. A key to all species and infraspecific taxa of therevised section Glaziovianae will appear in a forth-coming article by the author.M ATtEIAi.S ANI METHOD)S In this treatment the ranks "subspecies" and"variety" correspond to allopatry and sympatry, re-NOV)N 11: 157-165. 2001.