Bol.Soc.Bot.Méx. 83: 53-76 (2008) TAXONOMÍA Y FLORÍSTICA PLANT DIVERSITY ASSESSMENT IN THE Y AXCHILÁN NATURAL MONUMENT, CHIAPAS, MEXICO JORGE A. MEAVE1, 4, MARCO A. ROMERO-ROMERO1, ANDRÉS V ALLE-DOMÉNECH1, 2, ARMANDO RINCÓN-GUTIÉRREZ1, ESTEBAN MARTÍNEZ3 AND CLARA H. RAMOS3 1Departamento de Ecología y Recursos Naturales, Facultad de Ciencias, Universidad Nacional Autónoma de México, México 04510, D.F., México. 2Present address: El Colegio de la Frontera Sur, Unidad Villahermosa, Villahermosa, Tabasco, México. 3Departamento de Botánica, Instituto de Biología, Universidad Nacional Autónoma de México, México 04510, D.F, México. 4Author for correspondence. E-mail:
[email protected] Abstract: We assessed the diversity of vascular plants in the Yaxchilán Natural Monument, a nature protection area located in Chi- apas State, southern Mexico. A checklist including 547 species (337 genera, 102 families) was produced by combining information derived from three sources: (1) an initial list derived from an ecological study on forest structure; (2) a systematic survey conducted over an 18-month period; and (3) an extra visit to the site as part of a more ambitious project covering the entire Lacandon rain forest region. February was the month in which the largest number of fertile vouchers was collected in two consecutive years. The families with greatest richness were Fabaceae (47 species), Orchidaceae (34), Rubiaceae (23), and Asteraceae (22). The most spe- ciose genera were Piper (13 species), Psychotria (9), Adiantum and Peperomia (8). Trees were the largest growth form group (203 species), followed by terrestrial herbs (129). Most species (459) were encountered in primary, closed forest, but secondary vegeta- tion contributed 125 species.