Search Results (57)

Phyllosphere microbial communities influence the growth and productivity of plants, particularly in epiphytic plants, which are disconnected from nutrients available in the soil. We characterized the phyllosphere of 30 individuals of the epiphytic cycad, Zamia pseudoparasitica, collected from three forest sites during the rainy and dry seasons in the Republic of Panama. We used DNA metabarcoding to describe the total bacteria community with the 16S rRNA gene and the diazotrophic community with nifH gene. Common taxa included members of the Rhizobiales, Frankiales, Pseudonocardiales, Acetobacteriales, and the diazotrophic community was dominated by Cyanobacateria. We observed similar patterns of alpha diversity across sites and seasons, and no community differences were seen within sites between the rainy and dry seasons for either the 16S rRNA or nifH genes. However, pairwise comparisons showed some statistically significant differences in community composition between sites and seasons, but these explained only a small portion of the variation. Beta diversity partitioning indicated that communities were more phylogenetically closely related than expected by chance, indicative of strong environmental or host filtering shaping these phyllosphere communities. These results highlight the influence of host-driven selection and habitat stability in shaping phyllosphere microbiota, offering new insights into microbial assembly in tropical canopy ecosystems. Full article

Knowledge of propagation methods is crucial for conserving endangered plant species. Cycads are highly threatened, and propagation protocols using seeds and stem cuttings are well-understood. No air layer technique has been developed for cycad propagation, so the objective of this study was to develop a working protocol for adding this technique for cycad conservation. We opened wounds on mature Cycas edentata de Laub. stems to expose cortex and vascular tissue then installed an air layer medium to determine if adventitious roots would form. In one experiment, the peripheral vascular cylinder was exposed from 90° to 360°; in a second experiment, the use of auxin-promoting root stimulants was compared with a control group with no stimulants; and in a third experiment, the interior vascular cylinders were exposed in addition to the peripheral vascular cylinder. Every replication in every experiment developed adventitious roots beginning about 8 weeks and were ready to harvest with 10 cm roots by 14 weeks. The robust roots were about 1 cm in diameter, geotropic, and restricted to the outermost vascular cylinder exposed on the upper surface of the wounds. The number of roots and total root length per propagule increased by more than 300% as the percentage of exposed vascular tissue increased from 90° to 360°. Air layer techniques can be added to the cycad conservation toolbox, and its use may aid in conserving this threatened group of plants. Full article

Cycads, renowned as “living fossils”, are among the most ancient extant seed plants, playing a crucial role in understanding plant evolution and sex differentiation. Despite their importance, research on their genetics and sex differentiation remains scarce. This study investigates three species, represented by six samples, collected from various regions in Fujian Province, China, using whole-genome resequencing on the Illumina platform. The sequence data underwent rigorous quality control, alignment, and variant detection, focusing on SNP and InDel distribution and annotation. Among the studied species, Cycas revoluta exhibited the highest number of SNPs and the greatest heterozygosity values. Based on SNP data, phylogenetic trees and principal component analysis revealed distinct clusters, with the three C. revoluta samples forming one cluster, while the two C. szechuanensis samples and the C. taiwaniana sample were grouped separately. Gene function using COG and GO annotations, and KEGG enrichment analysis, all highlighted differences in genomic structure and functional gene distribution between male and female cycads. Notably, genes associated with sex differentiation, such as MADS-box and auxin-responsive protein genes, were shown, while other transcription factors showed distinct annotations and enrichment patterns based on sex. This study improves our understanding of genetic variation, evolutionary relationships, and gene enrichment in cycads, providing a foundation for conservation, cultivation, and insights into sex differentiation mechanisms in these ancient plants. Full article

The living gymnosperms include about 1200 species in five major groups: cycads, ginkgo, gnetophytes, Pinaceae (conifers I), and cupressophytes (conifers II). Molecular phylogenetic studies have yet to reach a unanimously agreed-upon relationship among them. Moreover, cytonuclear phylogenetic incongruence has been repeatedly observed in gymnosperms. We collated a comprehensive dataset from available genomes of 17 gymnosperms across the five major groups and added our own high-quality assembly of a species from Podocarpaceae (the second largest conifer family) to increase sampling width. We used these data to infer reconciled nuclear species phylogenies using two separate methods to ensure the robustness of our conclusions. We also reconstructed organelle phylogenomic trees from 42 mitochondrial and 82 plastid genes from 38 and 289 gymnosperm species across the five major groups, respectively. Our nuclear phylogeny consistently recovers the Ginkgo–cycads clade as the first lineage split from other gymnosperm clades and the Pinaceae as sister to gnetophytes (the Gnepines hypothesis). In contrast, the mitochondrial tree places cycads as the earliest lineage in gymnosperms and gnetophytes as sister to cupressophytes (the Gnecup hypothesis) while the plastomic tree supports the Ginkgo–cycads clade and gnetophytes as the sister to cupressophytes. We also examined the effect of mitochondrial RNA editing sites on the gymnosperm phylogeny by manipulating the nucleotide and amino acid sequences at these sites. Only complete removal of editing sites has an effect on phylogenetic inference, leading to a closer congruence between mitogenomic and nuclear phylogenies. This suggests that RNA editing sites carry a phylogenetic signal with distinct evolutionary traits. Full article

The Dzungaria Basin is located north of Xinjiang and is one of the largest inland basins in China. The eastern coalfields in the Dzungaria Basin contain a large amount of coal resources, and the thickness of the coal seams is significant. Therefore, the aim of this study was to classify the paleovegetation types and develop paleoclimate succession models of the extra-thick coal seams. We conducted the sampling, separation, and extraction of spores and pollen and carried out microscopic observations in the Wucaiwan mining area of the eastern coalfields in the Dzungaria Basin. The vertical vegetation succession in the thick seam (Aalenian Stage) in the study area was divided into three zones using the CONISS clustering method. The results show that the types of spore and pollen fossils belong to twenty families and forty-five genera, including twenty-three fern, twenty gymnosperm, and two bryophyte genera. The types of paleovegetation in the study area were mainly Lycopodiaceae and Selaginellaceae herb plants, Cyatheaceae, Osmundaceae, and Polypodiaceae shrub plants, and Cycadaceae and Pinaceae coniferous broad-leaved trees. The paleoclimate changed from warm–humid to humid–semi-humid and, finally, to the semi-humid–semi-dry type, all within a tropical–subtropical climate zone. The study area was divided into four paleovegetation communities: the nearshore wetland paleovegetation community, lowland cycad and Filicinae plant community, slope broad-leaved and coniferous plant mixed community, and highland coniferous tree community. This indicates that there was a climate warming event during the Middle Jurassic, which led to a large-scale lake transgression and regression in the basin. This resulted in the transfer of the coal-accumulating center from the west and southwest to the central part of the eastern coalfields in the Dzungaria Basin. Full article

Experimental manipulations of the balance between leaves as source organs and reproductive structures as sink organs have contributed greatly to our understanding of the assimilate partitioning and regulation of leaf photosynthesis. In order to add cycads to this research agenda, the full range in natural variation in leaf:seed ratio and incident light level of in situ Cycas micronesica was augmented with the experimental manipulation of leaf:seed ratios of C. micronesica and Cycas edentata in Guam and the Philippines. In every study, individual seed size and concentrations of megagametophyte carbon, starch, and sugars were not influenced by leaf:seed ratio. The leaf net photosynthesis (Pn) and operational efficiency of photosystem II were also quantified for the in situ studies, and leaf:seed ratio did not influence these leaf physiology traits. The natural variation in incident light revealed increased net Pn for C. micronesica trees receiving greater levels of light, but the sink traits of seeds were not influenced by these differences in source strength. The findings indicated that the size and sink activity of individual cycad seeds are constitutive traits that are not influenced by the relative balance between leaf source and seed sink size at the individual plant level. The results also reveal that upregulation or downregulation of cycad leaf Pn is not influenced by sink size or source:sink ratio. The massive amounts of nonstructural carbohydrates in cycad stems and roots may explain these findings, as these organs may be the primary source for strobilus and seed growth independently from leaf Pn. Full article

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

Recent technological advancements in conservation genetics and genomics have resulted in diverse tools for aiding the conservation of species. The precision and resolution of high throughput sequencing technologies provide valuable insights to aid conservation decisions, but these technologies are often financially unfeasible or unavailable in resource constrained countries. Inter-Simple Sequence Repeat (ISSR) markers, when combined with sensitive automated detection systems, provide a simple, cheap means to investigate genetic diversity and discriminate closely related species. Here, we apply this technology to assess genetic diversity and taxonomic delimitation in the Encephalartos eugene-maraisii species complex, a highly threatened, taxonomically dubious group of cycads in South Africa. Our analyses support the taxonomic singularity of E. dyerianus, E. dolomiticus and E. eugene-maraisii. Relationships between E. nubimontanus and E. cupidus remain uncertain. E. middelburgensis samples showed no clustering but had poor amplification success. This study demonstrates the suitability of automated ISSR fingerprinting as a method for plant conservation studies, especially in resource-constrained countries, and we make recommendations as to how this methodology can be effectively implemented. Full article

Gymnosperms originated in the Middle Devonian and have experienced a long evolutionary history with pulses of speciation and extinction, which resulted in the four morphologically distinct extant groups, i.e., cycads, Ginkgo, conifers and gnetophytes. For over a century, the systematic relationships within the extant gymnosperms have been debated because different authors emphasized different characters. Recent phylogenomic studies of gymnosperms have given a consistent topology, which aligns well with extant gymnosperms classified into three classes, five subclasses, eight orders, and 13 families. Here, we review the historical opinions of systematics of gymnosperms with special reference to several problematic taxa and reconsider the evolution of some key morphological characters previously emphasized by taxonomists within a phylogenomic context. We conclude that (1) cycads contain two families, i.e., the Cycadaceae and the Zamiaceae; (2) Ginkgo is sister to cycads but not to conifers, with the similarities between Ginkgo and conifers being the result of parallel evolution including a monopodial growth pattern, pycnoxylic wood in long shoots, and the compound female cones, and the reproductive similarities between Ginkgo and cycads are either synapomorphic or plesiomorphic, e.g., the boat-shaped pollen, the branched pollen tube, and the flagellate sperms; (3) conifers are paraphyletic with gnetophytes nested within them, thus gnetophytes are derived conifers, and our newly delimited coniferophytes are equivalent to the Pinopsida and include three subclasses, i.e., Pinidae, Gnetidae, and Cupressidae; (4) fleshy cones of conifers originated multiple times, the Podocarpaceae are sister to the Araucariaceae, the Cephalotaxaceae and the Taxaceae comprise a small clade, which is sister to the Cupressaceae; (5) the Cephalotaxaceae are distinct from the Taxaceae, because the former family possesses typical female cones and the fleshy part of the seed is derived from the fleshiness of integument, while the latter family has reduced female cones and preserves no traces of the seed scale complexes. Full article

It has been observed that the leaves of some Zamia species undergo a kind of “reverse ripening”; that is, they change from their original brown color to green during development. We assumed that this strange color change was due to the change in carotenoid composition, so we followed the changes for several weeks. The detailed carotenoid composition and content at different stages of development of the leaves was determined with HPLC-DAD focusing on the changes in red and yellow carotenoids. The total and relative amounts of red and yellow carotenoids were determined simultaneously from one measurement from a saponified and/or unsaponified extract. At the beginning of development, the concentration of red carotenoids was higher than that of the yellow ones; it decreased drastically until 22 days and continued to decrease slowly until they completely disappeared. The concentration of yellow carotenoids decreased at the beginning as well, but after 22 days it started to increase. The amount of red carotenoids started to decrease when the leaflet stopped growing. Lutein is the main component in old leaflets, which is not a red carotenoid precursor. Red carotenoids can always be found in their esterified form in the leaves. These findings support the hypothesis that red and yellow carotenoid accumulation are independent and probably have different functions in the leaflet. The strange color change was explained based on the compartmentalization of red and yellow carotenoids and on the changing activity of the enzyme capsanthin–capsorubin synthase responsible for the synthesis of red carotenoids capsorubin and capsanthin. Full article

Information on how bacteria in plants and soil, along with extracellular enzymes, affect nutrient cycling in Encephalartos villosus growing in phosphorus deficient and acidic scarp forests is lacking. Bacteria in coralloid roots, rhizosphere, and non-rhizosphere soils were isolated to determine the potential role of soil bacterial communities and their associated enzyme activities in nutrient contributions in rhizosphere and non-rhizosphere soils. The role of soil characteristics and associated bacteria on E. villosus nutrition and nitrogen source reliance was investigated. Encephalartos villosus leaves, coralloid roots, rhizosphere, and non-rhizosphere soils were collected at two scarp forests. Leaf nutrition, nitrogen source reliance, soil nutrition, and extracellular enzyme activities were assayed. A phylogenetic approach was used to determine the evolutionary relationship between identified bacterial nucleotide sequences. The clustering pattern of isolated bacterial strains was primarily dictated by the ecological niches from which they originated (rhizosphere soil, non-rhizosphere soil, and coralloid roots), thus indicating that host-microbe interactions may be a key driver of this pattern, in line with the hologenome theory. There were insignificant differences in the phosphorus and nitrogen cycling enzyme activities in E. villosus rhizosphere and non-rhizosphere soils in both localities. Significantly positive correlations were recorded between nitrogen and phosphorus cycling enzymes and phosphorus and nitrogen concentrations in rhizosphere and non-rhizosphere soils. Additionally, more than 70% of the leaf nitrogen was derived from the atmosphere. This study challenged the conventional expectation that environmental filters alone dictate microbial community composition in similar habitats and revealed that host-microbe interactions, as proposed by the hologenome theory, are significant drivers of microbial community structuring. The isolated bacteria and their plant growth promoting traits play a role in E. villosus nutrition and nitrogen source reliance and secrete nutrient cycling enzymes that promote nutrient availability in rhizosphere and non-rhizosphere soils. Full article

Translocation of endangered plant species and facilitating in situ regeneration require knowledge of the factors that define suitable habitat characteristics. Four approaches were employed to define how antecedent and contemporary plant identity influenced Cycas seedling growth and survival in Guam, Yap, and the Philippines. Cycas micronesica K.D. Hill or Cycas nitida K.D. Hill & A. Lindstr. seedlings growing beneath the canopy of the maternal parent tree reached 100% mortality in 4 to 8 year. Cycas micronesica seedlings planted beneath a conspecific male adult tree reached 68% mortality in two years while seedlings planted away from a conspecific individual exhibited 100% survival. Cycas micronesica seedlings planted beneath monostands of invasive Leucaena leucocephala (Lam.) de Wit or Vitex parviflora Juss. reached 40% mortality in two years while seedlings planted in adjacent native forest cover exhibited 100% survival. Cycas micronesica seedlings planted in soil conditioned for 9 months by conspecifics, heterospecific native species, Carica papaya L., L. leucocephala, or V. parviflora exhibited the greatest growth in the soils conditioned by heterospecific natives and the least growth in the soils conditioned by the three invasive species. The seedlings growing in soil conditioned by conspecifics exhibited the most coralloid roots and the greatest shoot:root ratio. These studies confirmed that the identity of antecedent and competitive plants strongly influenced the longevity and growth of Cycas seedlings. Conservationists may improve outcomes by avoiding degraded forests that have experienced invasive plant species when positioning translocation projects. Planting Cycas seedlings in biodiverse native forest but away from a conspecific individual may lead to the greatest success in population recovery. Full article

Stem cuttings are often exploited for asexual propagation of cycad plants, and impaired health of the source plants may reduce success. A reliable procedure that screens potential source plants for predicted success would benefit conservationists. The cut surfaces of Cycas revoluta stem cuttings obtained from source plants that had endured 0–39 weeks of Aulacaspis yasumatsui herbivory were stained with potassium triiodide to determine if this visual test could predict asexual propagation success. The stem cuttings were sorted into three groups based on stain intensity, then specific gravity and starch concentration of pith and cortex tissue were measured. The cuttings were maintained in a propagation nursery for 27 weeks, then root growth was quantified as dry weight. Specific gravity ranged from 1.01 to 1.11 and scaled linearly with starch concentration, which ranged from 16 to 195 mg·g⁻¹. The group of cuttings with the darkest stain intensity exhibited 100% propagation success with 23 g of roots per cutting, and the group with the least stain intensity exhibited 30% success with 2 g of roots per cutting. The group of stems with intermediate stain intensity exhibited intermediate values of every metric. These results indicated that cycad cuttings may be stained with iodine to estimate starch content in the field to provide an accurate instantaneous visual test for selection of the source plants that reliably generate the greatest level of asexual propagation success. 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

Cycads are the most threatened group in the plant kingdom. Fire is identified as one of the major factors heightening cycad extinction risk. However, compared to South American cycads, we know little about how fire negatively affects the demography of African cycads. Here, we collected a snapshot of demographic data on the largest known population of South Africa’s cycad species, Encephalartos lanatus, in unburnt and regularly burnt habitats. We fitted several statistical models to investigate the effects of fire on the population structure of E. lanatus. First, we found that the population follows a ‘J’ structure with more adults than any other life stage. Contrary to popular belief, this ‘J’ structure may not necessarily imply the future of the population is at risk, given that E. lanatus is a long-lived species. Second, we found that the abundance of adults explains 25% of the abundance of seedlings but does not predict the abundance of suckers, perhaps suggesting the adults ensure preferential seedling rather than clonal recruitment. Third, irrespective of life stages, the subpopulation in fire-prone habitats is, in term of size, proportionately lower than the subpopulation in unburnt areas, suggesting that fire may negatively affect the dynamic of the population. However, fire is not linked to differences in sex ratio across the population; not only do fire-prone subpopulations have more cones, but they also tend to have more damaged cones than unburnt populations. Overall, although we raised some limitations of the present study, we also inferred that fire may shape the observed ‘J’ structure of the population of E. lanatus, but, contrary to traditional belief, the ‘J’ structure is not enough to raise concern about the future of the population. A population dynamics study is required to determine if the future of the population is at risk. Full article