RESUMEN
BACKGROUND AND AIMS: The size and shape of reproductive structures is especially relevant in evolution because these characters are directly related to the capacity of pollination and seed dispersal, a process that plays a basic role in evolutionary patterns. The evolutionary trajectories of reproductive phenotypes in gymnosperms have received special attention in terms of pollination and innovations related to the emergence of the Spermatophytes. However, variability of reproductive structures, evolutionary trends and the role of environment in the evolution of cycad species have not been well documented and explored. This study considered this topic under an explicitly phylogenetic and evolutionary approach that included a broad sampling of reproductive structures in the genus Ceratozamia. METHODS: We sampled 1400 individuals of 36 Ceratozamia species to explore evolutionary pattern and identify and evaluate factors that potentially drove their evolution. We analyzed characters for both pollen and ovulate strobili within a phylogenetic framework using different methods and characters (i. e., molecular and both quantitative and qualitative morphological) to infer phylogenetic relationships. Using this phylogenetic framework, evolutionary models of trait evolution for strobilar size were evaluated. In addition, quantitative morphological variation and its relation to environmental variables across species were analyzed. KEY RESULTS: We found contrasting phylogenetic signals between characters of pollen and ovulate strobili. These structures exhibited high morphological disparity in several characters related to size. Results of analyses of evolutionary trajectories suggested a stabilizing selection model. In regards to phenotype-environment, the analysis produced mixed results and differences for groups in the vegetation type where the species occur; however, a positive relationship with climatic variables was found. CONCLUSIONS: The integrated approach synthesized reproductive phenotypic variation with current phylogenetic hypotheses and provided explicit statements of character evolution. The characters of volume for ovulate strobili were the most informative, which could provide a reference for further study of the evolutionary complexity in Ceratozamia. Finally, heterogeneous environments, which are under changing weather conditions, promote variability of reproductive structures.
RESUMEN
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. Ceratozamiaosbornei 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.
RESUMEN
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.
RESUMEN
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.
RESUMEN
A DNA barcoding study was conducted to determine the optimal combination of loci needed for successful species-level molecular identification in three extant cycad genera-Ceratozamia, Dioon, and Zamia-that occur in Mexico. Based on conclusions of a previous multigene study in representative species of all genera in the Cycadales, we tested the DNA barcoding performance of seven chloroplast coding (matK, rpoB, rpoC1, and rbcL) and non-coding (atpF/H, psbK/I, and trnH-psbA) regions, plus sequences of the nuclear internal transcribed spacer. We analysed data under the assumptions of the "character attributes organization system" (CAOS), a character-based approach in which species are identified through the presence of 'DNA diagnostics'. In Ceratozamia, four chloroplast regions and one nuclear region were needed to achieve > 70% unique species identification. In contrast, the two-gene combination atpF/H + psbK/I and the four-gene combination atpF/H + psbK/I + rpoC1 + ITS2 were needed to reach 79% and 75% unique species identification in Dioon and Zamia, respectively. The combinations atpF/H + psbK/I and atpF/H + psbK/I + rpoC1 + ITS2 include loci previously considered by the international DNA barcoding community. However, none of the three combinations of potential DNA barcoding loci found to be optimal with a character-based approach in the Mexican cycads coincides with the 'core barcode' of chloroplast markers (matK + rbcL) recently proposed for universal use in the plant kingdom.
RESUMEN
BACKGROUND AND AIMS: With the recent proposal of matK and rbcL as core plant DNA barcoding regions by the Consortium for the Barcoding of Life Plant Working Group, the construction of reference libraries in the botanical DNA barcoding initiative has entered a new phase. However, in a recent DNA barcoding study in the three Mexican genera of the gymnosperm order Cycadales, we found that neither matK nor rbcL allow high levels of molecular identification of previously established species. MATERIALS AND METHODS: Our data analysis in that study rested on the "Characteristic Attributes Organization System" (CAOS), a character-based algorithm for the definition of "DNA diagnostics." Here, we use CAOS to analyze a population-level molecular data set in Zamia, one of the three cycad genera occurring in Mexico, whose populations display contrasting biogeographic patterns. Our population-level study, which includes all species in the region formally known as Megamexico, is restricted to the genome region, which showed the best single-locus molecular identification performance in our previous study-namely, the noncoding intergenic chloroplast spacer psbK-I. RESULTS: Our comparison of single-individual vs. population-level psbK-I datasets in Zamia indicates that CAOS analyses are sensitive to slight alignment changes, which in turn derive from the different amounts of molecular variation present in each matrix type. CONCLUSION: We, therefore, suggest that character-based studies that involve population-level data should contemplate this type of comparison between data matrices, before a set of DNA diagnostics in a given DNA barcoding reference library is considered definitive.
