Arceo-Gómez, G. (Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Ave., Pittsburgh, PA, USA), M. L. Martínez (Red de Ecología Funcional, Instituto de Ecología A. C. carretera antigua a Coatepec N° 351 El Haya, Xalapa Veracruz, México C.P. 91070), V. Parra-Tabla (Departamento de Ecología Tropical, Campus de Ciencias Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Km. 15.5 carretera Mérida-Xmatkuil, Mérida, Yucatán, México), and J. G. García-Franco (Red de Ecología Funcional, Instituto de Ecología A. C. carretera antigua a Coatepec N° 351 El Haya, Xalapa Veracruz, México C.P. 91070). Floral and reproductive biology of the Mexican endemic Chamaecrista chamaecristoides (Fabaceae). J. Torrey Bot. Soc. 139: 260–269. 2012.—Chamaecrista chamaecristoides is an enantiostylous shrub endemic to the coast of Mexico that is being heavily impacted by human activities along the Gulf of Mexico. Chamaecrista chamaecristoides is considered a key species of the sand dune communities, particularly for its role as a nurse species and in dune stabilization. While certain aspects of its population biology have been well studied, others, such as its reproductive biology, have been overlooked. Understanding the factors that contribute to the successful reproduction of this species is crucial for its maintenance in natural populations. In this study, we examine the floral and reproductive biology of C. chamaecristoides. Specifically, we evaluate flower morphology and phenology, the breeding system and the identity and foraging patterns of floral visitors. Our results show that flower morphs are morphologically identical; however, position, size, and pollen production vary between stamens within each flower, suggesting functional differentiation. Furthermore, plants differ in their proportion of right- and left-styled flowers over the flowering season. While this could promote cross-fertilization by favoring pollen transfer among individuals with opposite floral-morph ratios, the presence of a stamen adjacent to the style, its self-compatibility and the absence of inbreeding depression all compromise the role of enantiostyly as an outcrossing strategy in this species. Finally, even though flowers are visited by at least ten different floral visitors, reproduction of C. chamaecristoides depends heavily on only three species that together account for more than 70% of the total number of visits. Overall, our results suggest that C. chamaecristoides is highly dependent on a small subset of the community of floral visitors and that it has evolved floral strategies to reduce pollen loss and enhance the efficiency of pollen transfer. For these reasons, future conservation strategies must also consider the preservation of suitable habitat for the somewhat limited pollinator community of this species.