Reestablishment of Zamia lawsoniana (Zamiaceae, Cycadales), an endemic species of Mexico, with first description of the ovulate strobilus

Background and Aims: Zamia, with 86 species, is the most diverse Neotropical cycad genus. In Mexico, 18 species occur, of which 15 are endemics. These taxa are distributed from sea level to 1200 m a.s.l. Recently, the phenology of Zamia in wild populations from southern Veracruz and Tabasco was studied to evaluate the morphological patterns of reproductive structures. While these records have been considered as Z. loddigesii, a species with a wide distribution along the Gulf of Mexico, different populations do possess morphological differences. Based on these data, we reevaluated the synonymy of Z. lawsoniana, which was described in 1884 and synonymized with Z. loddigesii in 1995. Methods: Botanical material was collected from three populations in Tabasco, ten in Veracruz and two in Oaxaca previously considered part of Z. loddigesii. Reproductive structures were measured at maturity in habitat. Populations were visited during 2022 and 2023 to record reproductive phenology. Herbarium specimens of Zamia lawsoniana and morphologically similar species (Z. loddigesii, Z. spartea and Z. stenophyllidia) were examined. A morphological description and an illustration for Z. lawsoniana were prepared. In addition, an identification key that included related species in terms of morphology, geography and phylogenetics was made. Key results: Zamia lawsoniana is removed from synonymy and some taxonomic clarifications are made. In this context, we provide a complete description of pollen strobili, including the microsporophylls, range of vegetative morphological variation, and a botanical illustration. Additionally, the ovulate strobilus is described for the first time and a preliminary conservation status is proposed. Conclusions: Based on morphological evidence of reproductive structures and vegetative characters, we propose the reestablishment of Zamia lawsoniana and its removal from synonymy with Z. loddigesii.