Search Results (8)

Ceratozamia chinantlensis sp. nov., a new cliff-dwelling cycad species from Sierra de La Chinantla, Oaxaca, Mexico, is described and compared with its congeners. The species is morphologically similar to Ceratozamia zoquorum and Ceratozamia santillanii, two geographically distant species, yet it is effortlessly distinguishable from its most proximally geographic congeners. Ceratozamia chinantlensis can be recognized based on several qualitative traits, such as its very coriaceous, long, linear to oblanceolate leaflets. Also, it has bronze-colored emerging leaves and mature leaves with articulations of a light copper color. Compared with C. zoquorum and C. santillanii, C. chinantlensis has significantly longer and wider leaflets. C. chinantlensis should be considered a critically threatened species due to its limited number of populations and individuals. Habitat destruction—historically through the extraction of Dioscorea mexicana and Vanilla planifolia, along with ongoing coffee and corn plantations—is an ongoing threat that narrows its distribution range. Full article

Heterocyte-forming cyanobacteria form symbiotic relationships with several lineages of plants. Here, twenty (20) strains of endosymbiotic cyanobacteria (cyanobionts) with Nostoc-like morphologies were isolated from the highly specialized coralloid roots of five host species in Cycadales—Cycas debaoensis, C. fairylakea, C. elongata, Ceratozamia robusta, and Macrozamia moorei. Molecular phylogeny based on the 16S rRNA gene placed these strains into seven different taxa within the Nostocaceae, specifically under the genera Desmonostoc and Dendronalium. The percent dissimilarity and unique patterns in the secondary structures of the D1-D1′, Box-B, V2, and V3 helices, which were based on the 16S–23S rRNA internal transcribed spacer (ITS) regions, supported three distinct species in Desmonostoc. These three morphologically distinct novel species are described in this report: Desmonostoc debaoense sp. nov., Desmonostoc meilinense sp. nov., and Desmonostoc xianhuense sp. nov. Other investigated strains were phylogenetically identified as members of the recently discovered genus Dendronalium and represent the first report of association of that genus with cycads. Our findings suggest that the order Cycadales hosts diverse species of cyanobionts in their coralloid roots and that many potential unreported or novel taxa are present in cycads occurring in their natural habitat and await discovery. Full article

Ceratozamia Brongn. is one of the species-rich genera of Cycadales comprising 38 species that are mainly distributed in Mexico, with a few species reported from neighboring regions. Phylogenetic relationships within the genus need detailed investigation based on extensive datasets and reliable systematic approaches. Therefore, we used 30 of the known 38 species to reconstruct the phylogeny based on transcriptome data of 3954 single-copy nuclear genes (SCGs) via coalescent and concatenated approaches and three comparative datasets (nt/nt12/aa). Based on all these methods, Ceratozamia is divided into six phylogenetic subclades within three major clades. There were a few discrepancies regarding phylogenetic position of some species within these subclades. Using these phylogenetic trees, biogeographic history and morphological diversity of the genus are explored. Ceratozamia originated from ancestors in southern Mexico since the mid-Miocene. There is a distinct distribution pattern of species through the Trans-Mexican Volcanic Belt (TMVB), that act as a barrier for the species dispersal at TMVB and its southern and northern part. Limited dispersal events occurred during the late Miocene, and maximum diversification happened during the Pliocene epoch. Our study provides a new insight into phylogenetic relationships, the origin and dispersal routes, and morphological diversity of the genus Ceratozamia. We also explain how past climatic changes affected the diversification of this Mesoamerica-native genus. Full article

Ceratozamia schiblii (Zamiaceae), a new species endemic to the highlands of eastern Oaxaca, Mexico, is described. The new species is part of the C. robusta species complex, which is a group of closely related species with very similar morphology. Among them, the new species can be distinguished by its brown leaflets in emerging leaves, a very long peduncle in seed cones, and the green color of mature pollen cones. Compared with the other species in the C. robusta species complex, C. schiblii has one of the longest rachides, and the highest number of leaflet pairs. The recognition of C. schiblii apparently resolves the total number of species within the C. robusta species complex. The region where C. schiblii populations occur coincides with the Neogene refugia areas of the Neotropical flora, which adds evidence to the importance of the mountain systems from Oaxaca and Chiapas, Mexico, in the diversification history of cycads. Full article

Ceratozamia dominguezii (Zamiaceae), a new species endemic to the lowland karstic tropical rainforests of southeastern Veracruz, Mexico, is described. The new species is part of the C. robusta species complex, a group of closely related species that share unique characteristics in the genus, such as robust trunks, large strobili, and long leaves. Compared with the other species in the complex (i.e., C. robusta, C. leptoceras, C. aurantiaca and C. subroseophylla), C. dominguezii has the longest rachides, and is characterized by having papyraceous leaflets, a unique caramel color in emerging leaves, and a dark-violet color in the central portion of distal faces of male and female sporophylls. Ceratozamia dominguezii occurs within the Uxpanapa floristic refuge, which is hypothesized to have sheltered a numerous group of tropical elements during the Neogene glaciations. The recognition of C. dominguezii contributes to clarifying the present diversity of cycads in the genus Ceratozamia, and adds discussion on the role of floristic refugia in the divergence of Neotropical plants in Mexico. Full article

Ceratozamia aurantiaca, a new cycad species from Oaxaca, Mexico, is described. The new species is endemic to lowland karst tropical rainforests of the northern mountains (Sierra Norte region). This species is related to C. subroseophylla and C. robusta, together considered part of the C. robusta species complex due to their shared characteristics: robust, upright trunk; large and long leaves with densely armed petioles and linear to subfalcate leaflets; and large megastrobili. Ceratozamia aurantiaca, as the epithet suggests, is easily distinguished from other species by the orange color of its emerging leaves, a trait unique in the genus. Additionally, C. aurantiaca is distinguished from C. subroseophylla and C. robusta by having significantly shorter petioles, wider spacing between leaflets, and wider median leaflets. The taxonomic recognition of this species represents a step toward clarifying species delimitation in the C. robusta complex. Full article

The literature containing which chemical elements are found in cycad leaves was reviewed to determine the range in values of concentrations reported for essential and beneficial elements. We found 46 of the 358 described cycad species had at least one element reported to date. The only genus that was missing from the data was Microcycas. Many of the species reports contained concentrations of one to several macronutrients and no other elements. The cycad leaves contained greater nitrogen and phosphorus concentrations than the reported means for plants throughout the world. Magnesium was identified as the macronutrient that has been least studied. Only 14 of the species were represented by data from in situ locations, with most of the data obtained from managed plants in botanic gardens. Leaf element concentrations were influenced by biotic factors such as plant size, leaf age, and leaflet position on the rachis. Leaf element concentrations were influenced by environmental factors such as incident light and soil nutrient concentrations within the root zone. These influential factors were missing from many of the reports, rendering the results ambiguous and comparisons among studies difficult. Future research should include the addition of more taxa, more in situ locations, the influence of season, and the influence of herbivory to more fully understand leaf nutrition for cycads. Full article

Two major lineages of beetles inhabit cycad cones in the New World: weevils (Curculionoidea) in the subtribe Allocorynina, including the genera Notorhopalotria Tang and O’Brien, Parallocorynus Voss, Protocorynus O’Brien and Tang and Rhopalotria Chevrolat, and beetles in the family Erotylidae, including the genus Pharaxonotha Reitter. Analysis of the 16S ribosomal RNA (rRNA) mitochondrial gene as well as cladistic analysis of morphological characters of the weevils indicate four major radiations, with a probable origin on the cycad genus Dioon Lindl. and comparatively recent host shifts onto Zamia L. Analysis of the 16S rRNA gene for erotylid beetles indicates that an undescribed genus restricted to New World Ceratozamia Brongn. is the most early-diverging clade, and this lineage is sister to a large radiation of the genus Pharaxonotha onto Zamia, with apparent host shifts onto Dioon and Ceratozamia. Analysis of beetles are in accord with current models of continental drift in the Caribbean basin, support some proposed species groupings of cycads, but not others, and suggest that pollinator type may impact population genetic structure in their host cycads. Full article