Ceratozamia is a genus of cycads occurring in eastern Mexico and Central America. In this study, we describe a new species from the Pacific region of Mexico in Guerrero state. This locality represents the most northwestern Mexico distribution for the genus. We focus the comparison of this species with the most geographically proximate and phenotypically relevant lineages for this taxon. We followed an integrative taxonomy approach to evaluate the classification of these species, including geographic location, morphology, DNA barcoding and phenology as primary sources of systematic data. Within the morphological dataset, reproductive structures are described in detail and new characters are proposed for microsporophylls. The comparative morphology of these structures facilitated the elucidation of differences in forms and species for identification. The two chosen DNA barcoding markers – namely, the chloroplast genome coding region matK and the nuclear ribosomal internal transcribed spacer (ITS) region – had low divergence, allowing only 61% of species identification, suggesting slow molecular evolutionary rates. Besides employing these three basic sources of evidence, we introduced phenology as additional information for species circumscription. In addition, this work includes a brief review of the genus at the species-level. This is therefore the most recent review for Ceratozamia across its full geographic range (latitudinal and elevational). Overall, this work further contributes to a comprehensive framework for systematic studies in Mexican cycads.

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A new species, from the montane region of Los Tuxtlas (state of Veracruz, Mexico), Ceratozamia subroseophylla, is proposed in accordance with the integrative taxonomy framework and through application of the taxonomic circle rationale. Our identification of this new species is the result of a thorough re-evaluation of four formerly described Ceratozamia species, namely: (1) C. miqueliana, with which it overlaps geographically; (2) C. mexicana; (3) C. robusta, which has also been previously seen as morphologically similar to C. miqueliana; and (4) C. brevifrons, which was at the center of a controversy concerning the morphological and geographic limits when compared to C. mexicana. Even though there are morphometric affinities of C. subroseophylla with this set of species, there are apomorphies in qualitative morphological characters and diagnostic nucleotidic variants established through character-based DNA barcoding to allow the recognition of this new species. The implications that our integrative taxonomy-based assessment of systematic diversity in Ceratozamia species from Veracruz have for evaluating the overall taxonomic status of the genus are discussed.

Taxonomía y sistemática Conceptos taxonómicos, fenología y epifitismo: el caso de Ceratozamia tenuis (Zamiaceae) Taxonomic concepts, phenology and epiphytism: the case of Ceratozamia tenuis (Zamiaceae)

The genus Ceratozamia is revised for the Sierra Madre Oriental in Mexico. This region is one of the biogeographic areas with the greatest diversity of species in this genus. These species are highly variable morphologically and this variability has led to a complex taxonomic history with many synonyms, particularly with reference to C. mexicana. We present a comprehensive taxonomic revision with history of nomenclature and the morphology, relationships, distribution and use of these species. We also introduce a key for their identification, descriptions, full synonymy, nomenclatural notes, etymologies and neotypes as well as taxonomic comments describing relevant taxonomic changes. We recognise fourteen species in this biogeographic province: C. brevifrons, C. chamberlainii, C. decumbens, C. delucana, C. fuscoviridis, C. hildae, C. kuesteriana, C. latifolia, C. mexicana, C. morettii, C. sabatoi, C. tenuis, C. totonacorum and C. zaragozae. This study provides a foundation for future taxonomic work in Neotropical species of Ceratozamia.