Swartzia mexicana (Fabaceae, Swartzieae), a New Species from Oaxaca, Mexico Mario Sousa S. Departalnento de Botanica, Institut dte Biologia, Universidad Nacional Aut6noma de Mexico. Apdo. Postal 70-367, 04510 Mexico, D.F. Mexico. [email protected] Rosaura Grether Departamnento de Biologia. Divisi6n de Ciencias Biol6gicas y de la Salud, Universidad Aut6noma Metropolitana-lztapalapa, Apdo. Postal 55-535, 09340 Mexico, D.F. Mexico. [email protected] STI \t :T. Swartzia mexicana, a new legumespecies from the State of Oaxaca. Mexico,. is de-scribed and illustrated. It is presently known onlyfrom the districts of Ixtlhn and Tuxtepec. The newspecies belongs to section Suartzin. subsectionSwartzia, and is assigned to series Tbunatene. With-in that series, it is closely related to S. sumorumby the leaflets not prominently reticulate, the styleuncinate. and the stigma truncate, as well as by thelegume elliptic in shape. A key to distinguish thenew species fromn S. sumorum and S. wuirdackii isprovided.RIE:S Ml:N. Se describe e ilustra Swatrtzi mexi-canat. uiia especie de leguminosas nueva para laciencia. del estado de Oaxaca. Mexico. Hasta ahorase conoee sl6o de los distritos de lxtlan y Tuxtepec.La especie nueva corresponde a la sect. Swartzia,subsect. Swartzia v se incluve en la serie Touna-teae. Dentro de esa serie, se relaciona estrecha-mente con S. sumorum por los foliolos sin nervacionreticulata prominente, el estilo uncitnado y el es-tigma truncado, asi como por la legulmbre de formaelfptica. Se presenta una clave para distinguir a laespecie nueva de S. sumorum v de S. wurdackii. Key words: Fabaceae, Mesoamerica. Mexico,Oaxaca. series Tounateae, Swartzia. Swarlzia is a neotropical genus of about 155 spe-cies. most of them found in South America. Onlytwo species are known to occur elsewhere, in trop-ical Africa. according to Cowan (1981). Species ofthe genus vary from small trees or shrubs (1.5-)3-18 m high. such as S. in/renusnta arneby and S.alato-sericea Barneby, to large trees up to 35-40 mihigh, such as S. gigantea R. S. Cowan and S. po-lyphylt I)DC. Some slender trees, such as S. pal-ustris Barneby. have occasionally sarmentosebranches. but the only species with a clamberinghabit is S. froesii K. S. Cowan. The genus is a com-mon component of lowland forests. especially alongrivers and in swampy forests. but in the Andeanarea it can be found from sea level up to 2100 melevation, as S. amplifodia Harms var. colombianaR. S. Cowan (Cowan, 1968: rarneby. 1991. 1996). In Mexico. Swartzia is found from Nayarit toChiapas along the Pacific slope, and it extendseastward to Veracruz, Tabasco. and the YucaadnPeninsula. Swartzia habitats include tropical rain-forests, semideciduous and deciduous forests, aswell as cloud forests. Besides Swartzia nexiucna.three other species of the genus are known to occurin Mexico: S. cubensis (Britton & V ilson) P. (.Standlev (Chiapas. Tabasco. Campeche. Yucatan.and Quintana Roo). S. myrtifolia J. E. Smith (\e-racruz, Oaxaca. Chiapas. Tabasco). and S. simplex(Swartz) Sprengel (Nayarit. Jalisco. Michoacan.Guerrero, Veracruz, Oaxaca. and Chiapas). In theState of Oaxaca, the latter two are allopatric to thenew species; they are found along the Pacific slopein the districts of Jamiltepec, Pochutla, and Juchi-tan, growing mainly in lowland forests. 200 to 78(m.s.m., although S. simplex has been collected upto 1660 m elevation in the District of Pochutla. Swurtzia cubensis also belongs to series i7ouna-tae; it is distinguished from S. mexicana by its mar-ginate to winged leaf rachis, shorter inflorescences.and yellow to orange, long stipitate, subglobose orovate, rostrate fruits. Swarizia myrtifolia and S. sim-plex are members of series Possir. T'heyI are dis-tinguished from the new species by their petalif-erous flowers, by the narrowly margined or wingedpetiole and leaf rachis, and by the subglobose oroblong fruits, very similar to those of S. cubensis. Mesoamerica is a more diverse region: alout 9to 12 species of Suartzia have been found fromnnorthern Oaxaea and the Isthmus of Tehuantepec. NoVON 12: 115-119. 2002.