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The reproductive phenology in plants consists of successive life cycle phases leading to reproductive success. In seed plants, cycads and other dioecious groups have complex reproductive systems, where individuals require synchronizations among two sexes and populations of the same species. Here, we analyzed phenology between populations of three geographically close species in the cycad genus Ceratozamia Brongn. We described the lifespan of pollen and ovulate strobili and their morphological changes throughout ontogeny and evaluated synchrony among reproductive events, focusing on the timing and abundance of the receptivity and open pollen phases. Our results showed that the reproductive timing in the three species was highly synchronous, and that the overlap between the receptivity and open pollen phases could point to gene flow among populations of different species. We identified a correlation between the reproductive patterns and the temperature and precipitation regimes. Pollen and ovulate strobili were produced during the rainy season, whereas the period of synchrony between receptivity and pollen occurred during the dry season. The seed release occurred during the rainy season, which could contribute to keep the seed moist and prevent the embryo from drying out. Finally, we highlight the utility of studies in wild populations for the ecological and evolutionary understanding of phenological patterns in cycads. 

Ceratozamia (Zamiaceae, Cycadales), is a member one of the most endangered seed plant groups. Species of Ceratozamia grow from near sea level up to 2,100 meters in Mexico and Mesoamerica. We present a modern taxonomic treatment of Ceratozamia , based on fieldwork combined with detailed study of herbarium specimens in and from Mexico and Central America. This new revision is based on incorporation of morphological, molecular and biogeographic data that have been previously published in circumscriptions of species complexes by our group. Detailed morphological descriptions of the 36 species of Ceratozamia are provided and relevant characters for the genus are discussed and described. A majority are endemic to Mexico and are concentrated at high elevations in mountainous areas. Synonymies, lectotypifications, etymologies, taxonomic notes, distribution maps, illustrations and detailed species-level comparisons are included, as well as a dichotomous key for identification of all species. Data on distributional ranges and habitats of all species are summarized. Ceratozamia osbornei D.W.Stev., Mart.-Domínguez & Nic.-Mor., sp. nov. is described from evergreen tropical forests of Belize and we highlight new populations and distributional ranges for C. subroseophylla Mart.-Domínguez & Nic.-Mor. and C. vovidesii Pérez-Farr. & Iglesias in the Mesoamerican region.