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1.
Ann Bot ; 128(5): 577-588, 2021 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-34265043

RESUMO

BACKGROUND AND AIMS: The gymnosperm order Cycadales is pivotal to our understanding of seed-plant phylogeny because of its phylogenetic placement close to the root node of extant spermatophytes and its combination of both derived and plesiomorphic character states. Although widely considered a 'living fossil' group, extant cycads display a high degree of morphological and anatomical variation. We investigate stomatal development in Zamiaceae to evaluate variation within the order and homologies between cycads and other seed plants. METHODS: Leaflets of seven species across five genera representing all major clades of Zamiaceae were examined at various stages of development using light microscopy and confocal microscopy. KEY RESULTS: All genera examined have lateral subsidiary cells of perigenous origin that differ from other pavement cells in mature leaflets and could have a role in stomatal physiology. Early epidermal patterning in a 'quartet' arrangement occurs in Ceratozamia, Zamia and Stangeria. Distal encircling cells, which are sclerified at maturity, are present in all genera except Bowenia, which shows relatively rapid elongation and differentiation of the pavement cells during leaflet development. CONCLUSIONS: Stomatal structure and development in Zamiaceae highlights some traits that are plesiomorphic in seed plants, including the presence of perigenous encircling subsidiary cells, and reveals a clear difference between the developmental trajectories of cycads and Bennettitales. Our study also shows an unexpected degree of variation among subclades in the family, potentially linked to differences in leaflet development and suggesting convergent evolution in cycads.


Assuntos
Zamiaceae , Cycadopsida , Fósseis , Filogenia , Sementes
2.
Carbohydr Polym ; 261: 117831, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33766335

RESUMO

Arabinogalactan-proteins (AGPs), important signalling molecules of the plant cell wall, are structurally extensively investigated in angiosperms, but information on AGPs in gymnosperms is still limited. We characterized AGPs from the gymnosperms Ginkgo biloba, Ephedra distachya, Encephalartos longifolius and Cycas revoluta. The protein contents are comparable to that of angiosperm AGPs. Hydroxyproline is the site of linking the carbohydrate part and was detected in all AGPs with highest concentration in Cycas AGP (1.1 % of the AGP). Interestingly, with the exception of Cycas, all AGPs contained the monosaccharide 3-O-methylrhamnose not present in angiosperm polysaccharides. The carbohydrate moieties of Cycas and Ephredra showed the main components 1,3,6-linked galactose and terminal arabinose typical of angiosperm AGPs, whereas that of Ginkgo AGP was unique with 1,4-linked galactose as dominant structural element. Bioinformatic search for glycosyltransferases in Ginkgo genome also revealed a lower number of galactosyltransferases responsible for biosynthesis of the 1,3-Gal/1,6-Gal AGP backbone.


Assuntos
Parede Celular/química , Cycadopsida/química , Mucoproteínas/química , Evolução Biológica , Sequência de Carboidratos , Parede Celular/metabolismo , Biologia Computacional , Cycadopsida/classificação , Cycadopsida/metabolismo , Cycas/química , Cycas/metabolismo , Ephedra/química , Ephedra/metabolismo , Galactanos/química , Ginkgo biloba/química , Ginkgo biloba/metabolismo , Estrutura Molecular , Mucoproteínas/isolamento & purificação , Mucoproteínas/metabolismo , Proteínas de Plantas/química , Proteínas de Plantas/isolamento & purificação , Proteínas de Plantas/metabolismo , Conformação Proteica , Zamiaceae/química , Zamiaceae/metabolismo
3.
Phytochemistry ; 186: 112715, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33721794

RESUMO

Cycad cone thermogenesis and its associated volatiles are intimately involved in mediating the behavior of their obligate specialist pollinators. In eastern Australia, thrips in the Cycadothrips chadwicki species complex are the sole pollinators of many Macrozamia cycads. Further, they feed and reproduce entirely in the pollen cones. M. miquelii, found only in the northern range of this genus, is pollinated only by a C. chadwicki cryptic species that is the most distantly related to others in the complex. We examined the volatile profile from M. miquelii pollen and ovulate (receptive and non-receptive) cones to determine how this mediates pollination mechanistically, using GC-MS (gas chromatography-mass spectrometry) and behavioral tests. Monoterpenes comprise the bulk of M. miquelii volatile emissions, as in other Macrozamia species, but we also identified compounds not reported previously in any cycad, including three aliphatic esters (prenyl acetate and two of uncertain identity) and two aliphatic alcohols. The two unknown esters were confirmed as prenyl (3-methylbut-2-enyl) esters of butyric and crotonic ((E))-but-2-enoic) acids after chemical synthesis. Prenyl crotonate is a major component in emissions from pollen and receptive ovulate cones, is essentially absent from non-receptive cones, and has not been reported from any other natural source. In field bioassays, Cycadothrips were attracted only to those volatile treatments containing prenyl crotonate. We discuss M. miquelii cone odorants relative to those of other cycads, especially with respect to prenyl crotonate being a species-specific signal to this northern C. chadwicki cryptic species, and how this system may have diversified.


Assuntos
Tisanópteros , Zamiaceae , Animais , Austrália , Flores , Polinização , Simbiose
4.
New Phytol ; 227(6): 1872-1884, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32392621

RESUMO

Niche conservatism is the tendency of lineages to retain the same niche as their ancestors. It constrains biological groups and prevents ecological divergence. However, theory predicts that niche conservatism can hinder gene flow, strengthen drift and increase local adaptation: does it mean that it also can facilitate speciation? Why does this happen? We aim to answer these questions. We examined the variation of chloroplast DNA, genome-wide single nucleotide polymorphisms, morphological traits and environmental variables across the Dioon merolae cycad populations. We tested geographical structure, scenarios of demographic history, and niche conservatism between population groups. Lineage divergence is associated with the presence of a geographical barrier consisting of unsuitable habitats for cycads. There is a clear genetic and morphological distinction between the geographical groups, suggesting allopatric divergence. However, even in contrasting available environmental conditions, groups retain their ancestral niche, supporting niche conservatism. Niche conservatism is a process that can promote speciation. In D. merolae, lineage divergence occurred because unsuitable habitats represented a barrier against gene flow, incurring populations to experience isolated demographic histories and disparate environmental conditions. This study explains why cycads, despite their ancient lineage origin and biological stasis, have been able to diversify into modern ecosystems worldwide.


Assuntos
Zamiaceae , Ecossistema , Especiação Genética , Geografia , México , Filogenia
5.
Mol Phylogenet Evol ; 139: 106530, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31176968

RESUMO

Evidence suggests that past climatic fluctuations affected speciation of extant cycads. However, empirical genetic and morphological evidence explaining patterns and processes of species diversification are scarce. There are some explanations for the origin and evolution of the genus Ceratozamia, but with inconclusive results. To elucidate the evolution of Ceratozamia, we used genetic and phenotypic sources as empirical data, which were applied in a 'proximate-ultimate' framework (ecological and evolutionary scale, respectively). Our results suggested that the evolutionary mechanisms of speciation were shaped by deterministic (natural selection-adaptation) driven by climatic conditions associated to water stress, and probably enhanced by stochastic processes (gene drift and inbreeding). In general terms, punctuated evolution models were those that best explained the patterns of speciation throughout the phylogenetic history of the lineages encompassed in the genus Ceratozamia. Finally, we provide empirical evidence on the tempo and mode of the evolution of a 'living plant fossil'.


Assuntos
Evolução Biológica , Zamiaceae/anatomia & histologia , Animais , Fósseis , Especiação Genética , Fenótipo , Filogenia , Filogeografia , Tamanho da Amostra , América do Sul , Especificidade da Espécie , Fatores de Tempo , Zamiaceae/genética
6.
PLoS One ; 14(2): e0211271, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30726265

RESUMO

Cycads are among the few plants that have developed specialized roots to host nitrogen-fixing bacteria. We describe the bacterial diversity of the coralloid roots from seven Dioon species and their surrounding rhizosphere and soil. Using 16S rRNA gene amplicon sequencing, we found that all coralloid roots are inhabited by a broad diversity of bacterial groups, including cyanobacteria and Rhizobiales among the most abundant groups. The diversity and composition of the endophytes are similar in the six Mexican species of Dioon that we evaluated, suggesting a recent divergence of Dioon populations and/or similar plant-driven restrictions in maintaining the coralloid root microbiome. Botanical garden samples and natural populations have a similar taxonomic composition, although the beta diversity differed between these populations. The rhizosphere surrounding the coralloid root serves as a reservoir and source of mostly diazotroph and plant growth-promoting groups that colonize the coralloid endosphere. In the case of cyanobacteria, the endosphere is enriched with Nostoc spp and Calothrix spp that are closely related to previously reported symbiont genera in cycads and other early divergent plants. The data reported here provide an in-depth taxonomic characterization of the bacterial community associated with coralloid root microbiome. The functional aspects of the endophytes, their biological interactions, and their evolutionary history are the next research step in this recently discovered diversity within the cycad coralloid root microbiome.


Assuntos
Bactérias Fixadoras de Nitrogênio/classificação , Análise de Sequência de DNA/métodos , Zamiaceae/microbiologia , Biodiversidade , DNA Ribossômico/genética , Endófitos/classificação , Endófitos/genética , Endófitos/isolamento & purificação , Bactérias Fixadoras de Nitrogênio/genética , Bactérias Fixadoras de Nitrogênio/isolamento & purificação , Filogenia , Raízes de Plantas/microbiologia , RNA Ribossômico 16S/genética , Rizosfera , Zamiaceae/classificação
7.
J Ethnobiol Ethnomed ; 15(1): 4, 2019 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-30658655

RESUMO

BACKGROUND: This study documents cycad-human relationships in Mexico, Belize, Guatemala, El Salvador, and Honduras over the last 6000 years. The impetus was acute need for a better understanding of previously undocumented uses of cycads in this region, and the need to improve cycad conservation strategies using ethnobotanical data. We hypothesized that cycads are significant dietary items with no long-term neurological effects, are important to religious practice, and contribute to cultural identity and sense of place, but that traditional knowledge and uses are rapidly eroding. Guiding questions focused on nomenclature, food and toxicity, relationships to palms and maize, land management issues, roles in religious ceremony, and medicinal uses, among others, and contributions of these to preservation of cycads. METHODS: From 2000 to 2017, the authors conducted 411 semi-structured ethnographic interviews, engaged in participant-observation in Mexican and Honduran communities, and carried out archival research and literature surveys. RESULTS: We documented 235 terms and associated uses that 28 ethnic groups have for 57 species in 19 languages across 21 Mexican states and 4 Central American nations. Carbohydrate-rich cycads have been both famine foods and staples for at least six millennia across the region and are still consumed in Mexico and Honduras. Certain parts are eaten without removing toxins, while seed and stem starches are detoxified via several complex processes. Leaves are incorporated into syncretic Roman Catholic-Mesoamerican religious ceremonies such as pilgrimages, Easter Week, and Day of the Dead. Cycads are often perceived as ancestors and protectors of maize, revealing a close relationship between both groups. Certain beliefs and practices give cycads prominent roles in conceptions of sense of place and cultural heritage. CONCLUSIONS: Cycads are still used as foods in many places. Though they do not appear to cause long-term neurological damage, their health effects are not fully understood. They are often important to religion and contribute to cultural identity and sense of place. However, because most traditional knowledge and uses are rapidly eroding, new community-based biocultural conservation efforts are needed. These should incorporate tradition where possible and seek inspiration from existing successful cases in Honduras and Mexico.


Assuntos
Etnobotânica , Zamiaceae , Belize , Culinária , El Salvador , Grupos Étnicos , Guatemala , Honduras , Humanos , Entrevistas como Assunto , México , Plantas Comestíveis , Plantas Medicinais , Terminologia como Assunto
8.
Pak J Biol Sci ; 22(10): 477-485, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31930837

RESUMO

BACKGROUND AND OBJECTIVE: Cycas revoluta and Zamia encephalartoides were commercially ornamental palms. Butterfly, Chilades pandava was an important pest of ornamental palms either cycas or zamia. Impact factors on C. pandava infestations on cycas and zamia palms were studied. MATERIALS AND METHOD: Two field experiments were carried out during the period from 1st January-15th December, 2018 in a private palm nursery at Abu-Ghaleb village, Giza, Egypt to study the infestation of C. pandava on cycas and zamia palms and also, provided its control strategies. RESULTS: The infested percent of C. pandava was recorded the highest values at 1st week of May and September, 2018 with 63.89 % on cycas palms. Whereas, the high value of the infestation percent was 66.67% on zamia palms. A positive effect was reported with maximum and minimum temperatures but a negative effect was recorded with average RH% on C. pandava infestations. The increasing of the C. pandava infestations decreased these 2 plant enzymes, peroxidase and phenoloxidase. The average reduction percentages of the tested 9 pesticides against C. pandava infestations on cycas palms were markedly higher in case of sulfur 70% SC and fipronil 80% WG being 69.88 and 61.30% reductions than other treatments after 3 sequential applications throughout 3 months, respectively. CONCLUSION: Chilades pandava infestation was higher on cycas palms than zamia palms. Sulfur and Fipronil were more efficacy pesticides against this pest.


Assuntos
Borboletas/fisiologia , Cycas/fisiologia , Inseticidas , Zamiaceae/fisiologia , Animais , Egito , Peroxidases/metabolismo , Controle de Pragas/métodos , Doenças das Plantas , Estações do Ano , Enxofre
9.
Zootaxa ; 4508(2): 151-178, 2018 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-30485971

RESUMO

Ceratophila new genus (Erotylidae: Pharaxonothinae) inhabiting male cones of the Mesoamerican cycad genus Ceratozamia Brongniart (Zamiaceae) is described for seven new species and compared to other genera of the Pharaxonothinae. Ceratophila differs from other genera of the Pharaxonothinae in many characters, most notable of which are: lateral pronotal carina thicker anteriorly in lateral view; head with supraocular and transverse occipital lines; elytra lacking a basal bead; and stridulatory files at base of head narrowly separated. Ceratophila has the male genitalia laterally compressed with a short median lobe and flagellum, similar to other Erotylidae. In comparison, the most superficially similar pharaxonothine genus Pharaxonotha Reitter has: lateral pronotal carina thin along entire length; head lacking supraocular lines, but with transverse occipital lines; elytra with distinct basal bead; stridulatory files at base of head widely separated; and unique male genitalia that are dorsoventrally flattened with a long median lobe and flagellum. Ceratophila contains two subgenera, which differ most notably in external characters and sexual dimorphism. Members of Ceratophila (Ceratophila), the nominal subgenus, have: more cylindrical bodies, pronotum evenly convex dorsally; the pronotum lacking basal longitudinal grooves on disc; metatibiae that are distinctly triangularly dilated toward apex; and no apparent external sexual dimorphism. In comparison, members of Ceratophila (Vovidesa) new subgenus have: dorsoventrally flattened bodies; the pronotum explanate (concave) along lateral margins; the pronotum with basal longitudinal grooves on disc; metatibiae weakly or not dilated toward apex; and with all tibiae in males showing strong sexual dimorphism. Four new species are described within the subgenus Ceratophila: C. (C.) chemnicki, C. (C.) gregoryi, C. (C.) picipennis, C. (C.) sanchezae; and three new species are described within the subgenus Vovidesa: C. (V.) chiapensis, C. (V.) mixeorum, C. (V.) vazquezi. Keys to genera, subgenera and species of known adults based on morphology are provided.


Assuntos
Besouros , Zamiaceae , Distribuição Animal , Estruturas Animais , Animais , Tamanho Corporal , Cycadopsida , Masculino , Tamanho do Órgão
10.
Am J Bot ; 105(9): 1512-1530, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30229556

RESUMO

PREMISE OF THE STUDY: Recent estimates of crown ages for cycad genera (Late Miocene) challenge us to consider what processes have produced the extant diversity of this ancient group in such relatively little time. Pleistocene climate change has driven major shifts in species distributions in Mexico and may have led to speciation in the genus Dioon by forcing populations to migrate up in elevation, thereby becoming separated by topography. METHODS: We inferred orthologs from transcriptomes of five species and sequenced these in 42 individuals representing all Dioon species. From these data and published plastid sequences, we inferred dated species trees and lineage-specific diversification rates. KEY RESULTS: Analyses of 84 newly sequenced nuclear orthologs and published plastid data confirm four major clades within Dioon, all of Pleistocene age. Gene tree analysis, divergence dates, and an increase in diversification rate support very recent and rapid divergence of extant taxa. CONCLUSIONS: This study confirms the Pleistocene age of Dioon species and implicates Pleistocene climate change and established topography in lineage spitting. These results add to our understanding of the cycads as evolutionarily dynamic lineages, not relicts or evolutionary dead ends. We also find that well-supported secondary calibration points can be reliable in the absence of fossils. Our hypothesis of lineage splitting mediated by habitat shifts may be applicable to other taxa that are restricted to elevation specific ecotones.


Assuntos
Zamiaceae , Biodiversidade , Evolução Biológica , Mudança Climática/história , História Antiga , Camada de Gelo , Zamiaceae/genética , Zamiaceae/fisiologia
11.
Ann Bot ; 121(3): 535-548, 2018 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-29293877

RESUMO

Background and Aims: Biogeographic transition zones are promising areas to study processes of biogeographic evolution and its influence on biological groups. The Mexican transition zone originated due to the overlap of Nearctic and Neotropical biota, which promoted great biological diversification. However, since most previous studies in this area were focused on revealing the phylogeography of Nearctic plants, how historical biogeographic configuration influenced the expansion and diversification of the Neotropical flora remains almost unknown. Using the cycad genus Dioon (Zamiaceae), this study aimed to test whether the biogeographic provinciality of the Mexican transition zone reflects the history of diversification of Neotropical plants. Methods: Two chloroplast DNA (cpDNA) regions were analysed from 101 specimens of 15 Dioon species to reveal the distribution of haplogroups. In addition, genome-wide single nucleotide polymorphisms (SNPs) from 84 specimens were used to test the concordance between phylogenetic clusters and the biogeographic provinces. An ultrametric tree was constructed from the sequences containing SNPs to reconstruct the biogeographic events of vicariance and dispersal of Dioon across the Neotropical biogeographic provinces. Key Results: Four Dioon lineages with strong phylogeographic structures were recognized using both cpDNA and SNP data. The lineages correspond to two clades that originated from a common ancestor in Eastern Mexico. One clade expanded and diversified in South-east Mexico and Central America. Another clade diversified into three lineages that dispersed to North-east, South and North-west Mexico. Each lineage was biogeographically delimitated. Biogeographic provinces might have provided disparate ecological conditions that facilitated speciation in Dioon since the Miocene. Conclusions: The current genetic structure and species diversity of Dioon depict the history of expansion and diversification of the northernmost Neotropical provinces. Past biogeographic connectivities were favoured by elevated topographies, since mountain systems served as corridors for the migration of Dioon and as refugia of tropical communities that diversified during the formation of modern Neotropical forests.


Assuntos
Zamiaceae/genética , América Central , DNA de Cloroplastos/genética , Variação Genética/genética , Haplótipos/genética , México , Filogenia , Filogeografia , Polimorfismo de Nucleotídeo Único/genética , Zamiaceae/anatomia & histologia
12.
Plant Biol (Stuttg) ; 20(3): 579-590, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29281847

RESUMO

Heat and odour production can have profound effects on pollination in cycads. It is therefore expected that these traits would co-vary geographically with pollinator assemblages. Such intraspecific variation, may lead to the evolution of pollination ecotypes, which can be an early stage of pollinator-mediated speciation. We measured cone temperatures using miniature temperature data loggers and examined the composition of cone volatile odours using headspace sampling and analysis with gas chromatography-mass spectrometry in four populations spanning the range of the African cycad Encephalartos ghellinckii. Pollinator assemblages were also investigated in three populations. Male and female cones were thermogenic at pollen shed and receptive stages, respectively, but patterns of thermogenesis did not vary among populations. Scent emissions from cones in populations in the Drakensberg Mountains were characterised by cis-ß-ocimene, ß-myrcene and (3E)-1,3-octadiene, while camphene and α-pinene were characteristic of scent emissions from cones in populations closer to the coast. These differences in volatile blends corresponded with differences in insect assemblages. These results confirm intraspecific variation in volatile emissions of E. ghellinckii and support the predictions that intraspecific variation in volatile emissions will be associated with shifts in pollinator assemblages. While further work needs to be done to test for local adaptation in this system, this preliminary evidence is consistent with the formation of pollination ecotypes in the E. ghellinckii species complex.


Assuntos
Insetos/fisiologia , Polinização/fisiologia , Zamiaceae/fisiologia , Animais , Biodiversidade , Flores/anatomia & histologia , Flores/fisiologia , Cromatografia Gasosa-Espectrometria de Massas , Odorantes , África do Sul , Termogênese/fisiologia , Compostos Orgânicos Voláteis/análise , Compostos Orgânicos Voláteis/metabolismo , Zamiaceae/anatomia & histologia
13.
J Hered ; 109(4): 438-445, 2018 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-29206927

RESUMO

Genetic diversity is key in providing the variation needed to face stochastic change. Increased habitat loss alters population size and dynamics posing serious threats to the conservation of wild species. Colombia has undergone massive deforestation over the last century, but harbors extraordinary high species diversity of genus Zamia (Cycadales); however, most of the species are under threat. In this study, we targeted the largest accessible remaining populations of 2 closely related species growing as endemics in the Magdalena Valley region of Colombia. We successfully transferred the SSR loci used in previous Zamia studies to these species. In total, we amplified 13 microsatellite loci in 3 wild populations, aiming at: 1) assessing genetic diversity and 2) understanding if the structure found between the 3 populations reflected species and population boundaries due to ecological and historical genetic isolation. We found that the actual population size does not reflect population genetic diversity with a small population (Perales) harboring the highest genetic diversity. In addition, all populations are highly structured regardless of species containment, all showing signs of genetic isolation. Given the high degree of ecological threat, and the inherent biological traits of Cycads, we provide information regarding the prioritization of populations for ex situ management.


Assuntos
Variação Genética , Genética Populacional , Repetições de Microssatélites/genética , Zamiaceae/genética , Colômbia , Conservação dos Recursos Naturais , Ecossistema , Espécies em Perigo de Extinção , Filogenia
14.
Ann Bot ; 121(1): 47-60, 2018 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-29155921

RESUMO

Background and Aims: Aridification is considered a selective pressure that might have influenced plant diversification. It is suggested that plants adapted to aridity diversified during the Miocene, an epoch of global aridification (≈15 million years ago). However, evidence supporting diversification being a direct response to aridity is scarce, and multidisciplinary evidence, besides just phylogenetic estimations, is necessary to support the idea that aridification has driven diversification. The cycad genus Dioon (Zamiaceae), a tropical group including species occurring from humid forests to arid zones, was investigated as a promising study system to understand the associations among habitat shifts, diversification times, the evolution of leaf epidermal adaptations, and aridification of Mexico. Methods: A phylogenetic tree was constructed from seven chloroplast DNA sequences and the ITS2 spacer to reveal the relationships among 14 Dioon species from habitats ranging from humid forests to deserts. Divergence times were estimated and the habitat shifts throughout Dioon phylogeny were detected. The epidermal anatomy among Dioon species was compared and correlation tests were performed to associate the epidermal variations with habitat parameters. Key Results: Events of habitat shifts towards arid zones happened exclusively in one of the two main clades of Dioon. Such habitat shifts happened during the species diversification of Dioon, mainly during the Miocene. Comparative anatomy showed epidermal differences between species from arid and mesic habitats. The variation of epidermal structures was found to be correlated with habitat parameters. Also, most of the analysed epidermal traits showed significant phylogenetic signals. Conclusions: The diversification of Dioon has been driven by the aridification of Mexico. The Miocene timing corresponds to the expansion of arid zones that embedded the ancestral Dioon populations. As response, species in arid zones evolved epidermal traits to counteract aridity stress. This case study provides a robust body of evidence supporting the idea that aridification is an important driver of biodiversity.


Assuntos
Evolução Biológica , Mudança Climática , Zamiaceae/genética , Biodiversidade , Clima Desértico , Ecossistema , Filogenia , Epiderme Vegetal/anatomia & histologia , Chuva , Zamiaceae/anatomia & histologia
15.
Am J Bot ; 104(5): 757-771, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28515078

RESUMO

PREMISE OF THE STUDY: The Bahamas archipelago is formed by young, tectonically stable carbonate banks that harbor direct geological evidence of global ice-volume changes. We sought to detect signatures of major changes on gene flow patterns and reconstruct the phylogeographic history of the monophyletic Zamia pumila complex across the Bahamas. METHODS: Nuclear molecular markers with both high and low mutation rates were used to capture two different time scale signatures and test several gene flow and demographic hypotheses. KEY RESULTS: Single-copy nuclear genes unveiled apparent ancestral admixture on Andros, suggesting a significant role of this island as main hub of diversity of the archipelago. We detected demographic and spatial expansion of the Zamia pumila complex on both paleo-provinces around the Piacenzian (Pliocene)/Gelasian (Pleistocene). Populations evidenced signatures of different migration models that have occurred at two different times. Populations on Long Island (Z. lucayana) may either represent a secondary colonization of the Bahamas by Zamia or a rapid and early-divergence event of at least one population on the Bahamas. CONCLUSIONS: Despite changes in migration patterns with global climate, expected heterozygosity with both marker systems remains within the range reported for cycads, but with significant levels of increased inbreeding detected by the microsatellites. This finding is likely associated with reduced gene flow between and within paleo-provinces, accompanied by genetic drift, as rising seas enforced isolation. Our study highlights the importance of the maintenance of the predominant direction of genetic exchange and the role of overseas dispersion among the islands during climate oscillations.


Assuntos
Biodiversidade , Filogenia , Zamiaceae/genética , Bahamas , Variação Genética , Ilhas , Repetições de Microssatélites , Filogeografia
16.
Rev Biol Trop ; 65(1): 305-19, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29466646

RESUMO

The Ceratozamia norstogii complex from Southern Mexico is made up of four closely related taxa and occurs in similar habitats (Quercus forest). All have linear-lanceolate leaflets with great similarity between them, especially in juvenile stages, but differentiate with age. There has been debate regarding delimitation of species due to character loss in herbarium specimens. The aim of this study was to determine the genetic variation, and to measure genetic similarity between the four taxa. We studied populations in Cintalapa (Chiapas) for C. alvarezii and C. norstogii; the Sierra Atravesada (Oaxaca) for C. chimalapensis, and Villa Flores (Chiapas) for C. mirandae. One population for each taxon was sampled (only one population is known for C. alvarezii) 11-15 randomly chosen adult individuals were sampled. Twenty-eight primers were tested of which five were polymorphic using the RAPD'S technique. The data were analyzed using Bayesian methods. Results revealed low genetic diversity, and a differentiation was found between species, suggesting a recent divergence. A previous morphological and anatomical study on the complex has found the taxa to be distinct. However, the results of this study have shown that the C. norstogii species complex is in a divergence process, probably through genetic drift and founder effects.


Assuntos
Variação Genética , Dispersão Vegetal , Zamiaceae/genética , Teorema de Bayes , Biodiversidade , Marcadores Genéticos , México , Técnica de Amplificação ao Acaso de DNA Polimórfico/métodos , Valores de Referência , Especificidade da Espécie
17.
J Chem Ecol ; 42(11): 1142-1150, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27704314

RESUMO

Plants have multiple strategies, including phytochemicals that protect their vulnerable tissues against pathogens and herbivores. Dioon edule, like all cycads, possess unique azoxy-type compounds, azoxyglycosides (AZGs) as a chemical defense; however, the ontogenetic variability of these compounds in this long-lived cycad is unknown. Here, we investigated the effects of plant age, sex, genotype and individual heterozygosity on AZG levels in mature leaves of wild D. edule populations from eastern Mexico. Individuals were divided into three ontogenetic stages: seedlings, juveniles and adults. We established overall leaf quality by quantifying pigments associated with photosynthesis; chlorophylla, chlorophyllb and lutein. Leaf chlorophylla levels were higher in seedlings compared to adult cycads. Plants were genotyped using 11 microsatellite markers and foliar AZG levels were quantified by HPLC. AZG levels do not correlate with plant genotype or the individual's heterozygosity. Genetic analysis identified a distinction between lowland and highland individuals; foliar AZG levels were higher in lowland adult cycads compared to highland individuals. In both populations, the highest AZG levels were found in seedlings compared to adult cycads. These young cycads are highly reliant on their few leaves since seedlings bear one or two leaves for the first years of their life and, thus, are unlikely to recover from defoliation. The results suggest that cycad leaves with a greater nutritive content and a higher value for long-term survival are better protected with higher AZG levels. Female adult cycads have higher AZG levels compared to males, suggesting that the benefits of defense could also be linked to reproductive costs.


Assuntos
Glicosídeos/metabolismo , Folhas de Planta/metabolismo , Zamiaceae/crescimento & desenvolvimento , Zamiaceae/metabolismo , Ontologias Biológicas , Heterozigoto , Pigmentos Biológicos/metabolismo , Zamiaceae/genética
18.
Plant Cell Environ ; 39(7): 1588-600, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26924274

RESUMO

An important outcome of plant thermogenesis is increased emissions of volatiles that mediate pollinator behaviour. We investigated whether the large increase in emissions, mainly the monoterpene ß-myrcene (>90%), during daily thermogenic events of Macrozamia macleayi and lucida cycad cones are due solely to the influence of high cone temperatures or are, instead, a result of increased respiratory rates during thermogenesis. We concurrently measured temperature, oxygen consumption and ß-myrcene emission profiles during thermogenesis of pollen cones under typical environmental temperatures and during experimental manipulations of cone temperatures and aerobic conditions, all in the dark. The exponential rise in ß-myrcene emissions never occurred without a prior, large increase in respiration, whereas an increase in cone temperature alone did not increase emissions. When respiration during thermogenesis was interrupted by anoxic conditions, ß-myrcene emissions decreased. The increased emission rates are not a result of increased cone temperature per se (through increased enzyme activity or volatilization of stored volatiles) but are dependent on biosynthetic pathways associated with increased respiration during thermogenesis that provide the carbon, energy (ATP) and reducing compounds (NADPH) required for ß-myrcene production through the methylerythritol phosphate (MEP) pathway. These findings establish the significant contribution of respiration to volatile production during thermogenesis.


Assuntos
Monoterpenos/metabolismo , Termogênese , Compostos Orgânicos Voláteis/metabolismo , Zamiaceae/metabolismo , Monoterpenos Acíclicos , Respiração Celular , Oxigênio/metabolismo , Temperatura
19.
Proc Biol Sci ; 282(1816): 20152053, 2015 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-26446814

RESUMO

Brood-site mutualisms represent extreme levels of reciprocal specialization between plants and insect pollinators, raising questions about whether these mutualisms are mediated by volatile signals and whether these signals and insect responses to them covary geographically in a manner expected from coevolution. Cycads are an ancient plant lineage in which almost all extant species are pollinated through brood-site mutualisms with insects. We investigated whether volatile emissions and insect olfactory responses are matched across the distribution range of the African cycad Encephalartos villosus. This cycad species is pollinated by the same beetle species across its distribution, but cone volatile emissions are dominated by alkenes in northern populations, and by monoterpenes and a pyrazine compound in southern populations. In reciprocal choice experiments, insects chose the scent of cones from the local region over that of cones from the other region. Antennae of beetles from northern populations responded mainly to alkenes, while those of beetles from southern populations responded mainly to pyrazine. In bioassay experiments, beetles were most strongly attracted to alkenes in northern populations and to the pyrazine compound in southern populations. Geographical matching of cone volatiles and pollinator olfactory preference is consistent with coevolution in this specialized mutualism.


Assuntos
Besouros/fisiologia , Polinização , Simbiose , Compostos Orgânicos Voláteis/metabolismo , Zamiaceae/fisiologia , Animais , Evolução Biológica , Geografia , Odorantes/análise , Percepção Olfatória , África do Sul
20.
Am J Bot ; 102(7): 1061-72, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26199364

RESUMO

UNLABELLED: • PREMISE OF THE STUDY: Spatiotemporal features of microsporogenesis may provide important clues about the evolution of microsporogenesis in seed plants. One cellular feature that attracts special attention is advance cell wall ingrowths (ACWIs) at future cytokinetic sites in microsporocytes since they have been found only in species of an ancient lineage of angiosperms, Magnolia, and in much less detail, of an ancient lineage of gymnosperms, cycads. Further investigation into microsporogenesis in a cycad species may yield knowledge critical to understanding the establishment of ACWIs as an important feature for comparative studies of microsporogenesis in seed plants.• METHODS: Bright-field and epifluorescence microscopy, confocal laser scanning microscopy, and transmission electron microscopy were used to investigate the microsporogenic process in Macrozamia communis, a species in the Zamiaceae family of cycads.• KEY RESULTS: In prophase-II microsporocytes in M. communis, ACWIs form as a callose ring between the newly formed nuclei and are not accompanied by cytokinetic apparatuses such as mini-phragmoplasts, wide tubules, or wide tubular networks. Shortly after the second nuclear division, new ACWIs, albeit thinner than the previous ACWIs, form between the newly formed nuclei. Subsequent cell plate formation in the planes of the ACWIs typically results in tetragonal tetrads.• CONCLUSIONS: Cytokinesis at the cell periphery is initiated earlier than cell plate formation in the cell interior in microsporogenesis in M. communis. The cellular features uncovered in M. communis may serve as useful reference features for comparative studies of microsporogenesis in plants.


Assuntos
Citocinese , Gametogênese Vegetal , Sementes/fisiologia , Zamiaceae/fisiologia , Evolução Biológica , Parede Celular/metabolismo , Parede Celular/ultraestrutura , Células Germinativas Vegetais/fisiologia , Células Germinativas Vegetais/ultraestrutura , Glucanos/metabolismo , Sementes/ultraestrutura , Análise Espaço-Temporal , Zamiaceae/ultraestrutura
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