Instituto de Botánica Darwinion
  • Darwin, Buenos Aires, Argentina
Recent publications
Auxin has a central role in determining tomato fruit growth and development, and most of its action is mediated by gibberellins (GAs). The diageotropica (dgt) mutant of tomato exhibits many physiological responses that are related to a defective auxin sensitivity. In this paper we investigated the effects of the dgt mutation on tomato gibberellin biosynthesis regulation during fruit-set and early growth of pollinated fruits. In spite of an initial accumulation of active GAs in dgt ovaries, their content is significantly reduced at later stages. Indeed, at the beginning of rapid fruit growth, dgt fruits display a lower amount of GA1 and its direct catabolite GA8. Consistently, transcripts of GA 20-oxidase genes (GA20ox1, GA20ox2, GA20ox3) are low in the mutant. Moreover, low expression of genes encoding GA catabolism enzymes (GA 2β-hydroxylases) does not lead to an increase in the amount of active GAs, supporting the hypothesis that GA 20-oxidase genes downregulation might bottleneck the synthesis of active GAs in dgt. Interestingly, exogenous GA3 application has little effect on dgt ovaries. GA3-treated fruits of the mutant are smaller than those of its wild type as a result of fewer and smaller pericarp cells. Consistently, GA3 treatment in the dgt ovaries produces negligible effects on cell endoreduplication revealed by a lower nuclear DNA content in pericarp and locular tissue cells. The lack of DELLA-mediated constraint on GA signal in the double mutant dgt pro did not cause an increase in size and weight in pollinated fruits, suggesting that GA signalling is unable to overcome the inhibition of growth caused by the dgt mutation.
The leaf morphology of Selaginella species from subtropical South America show differences in structure and ultrastructure that are useful for species identification. We studied the following epidermal traits: micromorphology of stomatal types, distribution patterns of silica cells, silica cells and silica bodies of Selaginella convoluta, S. microphylla, S. sellowii and S. sulcata, using light and scanning electron microscopy. Five stomatal types were observed, anomocytic, actinocytic, anisocytic, staurocytic and tetracytic and two additional variants, anomodiacytic and anomoparacytic. Five silica cell distribution patterns were identified, laminar, medial, medial-basiscopic, subcostal, and submarginal. Pyramidal silica bodies and conical bodies with concave base are described for the first time. In the studied species, silica bodies are pyramidal in S. convoluta and globular, conical and pyramidal in S. microphylla, whereas in S. sellowii and S. sulcata they are conical, with concave base of different sizes. Illustrations of the epidermal features, LM photographs, SEM micrographs and comparative tables are presented.
The Yabotí Biosphere Reserve (Prov. Misiones, Argentina) with 221,155 ha, represents one of the southernmost relicts of the Paranaense forest. Currently, a project is being developed in the area to inventory and describe the ferns and lycophytes. As a result of these studies, we identify a new species of Amauropelta, A. yabotiensis. Within this genus, it belongs to the group of species with uncinate hairs and presents a unique combination of diagnostic features, including the type of pubescence on the rhizome scales, the shape of the fronds and segments and type of venation. Here, we described and illustrated the species and we analyzed its taxonomic affi nities and geographic distribution. Additionally, we provided a distribution map and a key to distinguish it from other Amauropelta species from Misiones province. With this new fi nding, we highlighted the importance of the Yabotí Reserve as a reservoir of biodiversity in the region.
The Andean region is one of the most biodiverse areas, displaying high levels of endemism and spatial turnover of species. Tribe Eudemeae includes nine genera and 40 species distributed from the northern Andes in Colombia to the southernmost portion of the Andes in Argentina and Chile. Here, we generated a species-level phylogenetic tree to study their climatic niche evolution. We first analysed phylogenetic structure and evolutionary shifts among the main climatic spaces using model-based estimates. Second, we estimated climatic niches for each species and compared them in a phylogenetic context. In Eudemeae, three main groups of climatic spaces were found, mainly related to the northern and central Andes, the north-central portion of the southern Andes and the central-southern portion of the southern Andes. Results suggest that initial colonization of new climatic spaces in the evolution of the tribe appears to be promoted through shifts in adaptive regimes, whereas subsequent diversification of genera occurred predominantly under the same climatic regimes. This trade-off between niche conservatism and divergence appears to have modulated their diversification across the Andes and contributed to their current geographical distribution.
Stachytarpheta is one of the most speciose genera of Verbenaceae in Brazil with a high rate of endemism. Stachytarpheta olearyana P.H.Cardoso and S. vianae P.H.Cardoso, two new species endemic to the Espinhaço Range in the state of Minas Gerais, eastern Brazil, are here described and illustrated. Both species have a restricted distribution and are assessed as Critically Endangered (CR). Detailed diagnosis, morphological comparisons, ecological data, and a distribution map are provided for each species.
Full plastome sequences for land plants have become readily accessible thanks to the development of Next Generation Sequencing (NGS) techniques and powerful bioinformatic tools. Despite this vast amount of genomic data, some lineages remain understudied. Full plastome sequences from the highly diverse (>1,500 spp.) subfamily Tillandsioideae (Bromeliaceae, Poales) have been published for only three (i.e., Guzmania, Tillandsia, and Vriesea) out of 22 currently recognized genera. Here, we focus on core Tillandsioideae, a clade within subfamily Tillandsioideae, and explore the contribution of individual plastid markers and data categories to inform deep divergences of a plastome phylogeny. We generated 37 high quality plastome assemblies and performed a comparative analysis in terms of plastome structure, size, gene content and order, GC content, as well as number and type of repeat motifs. Using the obtained phylogenetic context, we reconstructed the evolution of these plastome attributes and assessed if significant shifts on the evolutionary traits’ rates have occurred in the evolution of the core Tillandsioideae. Our results agree with previously published phylogenetic hypotheses based on plastid data, providing stronger statistical support for some recalcitrant nodes. However, phylogenetic discordance with previously published nuclear marker-based hypotheses was found. Several plastid markers that have been consistently used to address phylogenetic relationships within Tillandsioideae were highly informative for the retrieved plastome phylogeny and further loci are here identified as promising additional markers for future studies. New lineage-specific plastome rearrangements were found to support recently adopted taxonomic groups, including large inversions, as well as expansions and contractions of the inverted repeats. Evolutionary trait rate shifts associated with changes in size and GC content of the plastome regions were found across the phylogeny of core Tillandsioideae.
One of the main intoxications to livestock in the Patagonia region of Argentina is the tremorgenic disease “Mal de Huecú", attributed to the consumption of the native grasses Poa huecu and/or Festuca argentina. In this report, five outbreaks of spontaneous intoxications were investigated.Several indole-diterpene alkaloids were identified in Poa huecu and Festuca argentina including the known tremorgen terpendole C and are likely the cause of “Mal de Huecú" disease.
Verbenaceae are a distinctive element from the Americas, and even when there are numerous useful species in the family until now they have not been listed. In line with this, we present the first checklist of Verbenaceae employed for food purposes in the continent. Seventy two bibliographical sources mentioning at least one edible Verbenaceae were selected from more than 500 references analyzed; as a result, 46 edible species have been registered. The family stands in the Americas regarding the use of aromatic plants. In fact, ca. 40% of the edible species are employed because of their aromatic traits, followed by edible fruits (ca. 33%). This collaborative effort represents a baseline for future research on this valuable lineage of flowering plants. Available at http://www.ojs.darwin.edu.ar/index.php/darwiniana/article/view/1023
This article is the first contribution to the characterization of monofloral honeys from the Dry and Humid Chaco that combines palynological and physicochemical parameters. The study focuses on the most represented honeys. Physicochemical parameters such as color, electrical conductivity, moisture, acidity and pH were analyzed for a total of 116 honeys classified as monofloral by pollen analysis. All the parameters considered were within the accepted range. Color and electrical conductivity were the most distinctive features, as stressed by multivariate (cluster analysis (CA) and principal component analysis (PCA)) and correlation analysis. The darkest honeys (i.e. black, dark amber and amber) were those from Tessaria integrifolia, Schinopsis balansae, S. lorentzii and Baccharis–Eupatorium-type pollen, and the lightest honeys (i.e. light amber and extra light amber) were those from Cynophalla retusa, Eugenia uniflora, Copernicia alba, Prosopis alba and Helianthus annuus. Mean values for electrical conductivity ranged from 0.4 to 0.8 mS cm−1, with the highest values detected in the darkest honeys, which are mainly produced in the Dry Chaco. The intense color of these honeys also suggests the presence of antioxidants. Thus, the color, electrical conductivity and antioxidant properties are important factors for future research to consider, to obtain a reliable authentication of the botanical and geographical features of these honeys.
The available taxonomic literature on the Argentinian species of Johnstonella is far from reflecting the phylogenetic relationships of the lineage as they are known today. For this reason, an updated taxonomic treatment of the genus in Argentina is reported in this contribution. As a result, a complete synonymy is provided for the accepted species, as well as morphological descriptions, geographical distribution maps, an identification key, uses, illustrations, photographs, and estimates of their conservation status. Additionally, lectotypes are designated for the names Cryptantha capituliflora var. compacta, Cryptantha hossei, Cryptantha modesta, Eritrichium falcatum, and Myosotis albida, as well as a second-step lectotype for Eritrichium axillare.
Cortesia is a halophytic and monotypic genus endemic to Argentina that belongs to Ehretiaceae (Boraginales). It is morphologically distinct from the other members of the family in having cuneate leaves with a 3-dentate apex, an involucrum of fused bracts, spatulate calyx lobes, and white drupes with a two-parted endocarp. Its single species, Cortesia cuneifolia, is here treated and illustrated based on the study of numerous herbarium collections. Additionally, a lectotype is designated for the name to assure its reliable application. Furthermore, the species is recorded for the first time in Tucumán province. Available at http://www.ojs.darwin.edu.ar/index.php/darwiniana/article/view/1034/1259
Turnera sidoides (x=7) is one of the few well-studied South American autopolyploid complexes. Since polyploidy has played a prominent role within this complex, ongoing studies in T. sidoides focus on understanding the mechanisms involved in the origin and the establishment of polyploids using integrative approaches. This paper synthesises the results of more than 20 years of research on this topic. Cytogenetics analysis provided evidences for the production of unreduced male and female gametes, supporting the hypothesis of bilateral sexual polyploidization as the mechanism of origin of polyploids in T. sidoides. The finding of viable triploids suggested that unilateral sexual polyploidization could also be an important mechanism for the origin of tetraploids in T. sidoides. The occurrence of plants continuously forming many unreduced gametes would play a key role in the establishment of neopolyploids in natural populations. Also, the higher number of propagules that tetraploids contribute to subsequent generations, the ability to multiply asexually by rhizomes, and the occurrence of occasional cases of self-compatibility and successful illegitimate crosses in polyploids increase the likelihood that a low frequency of neopolyploids can be maintained in natural populations of T. sidoides. In addition, integration of cytogeographic and genetic divergence data together with past niche modelling provided further insights supporting the hypothesis that historical climatic and geomorphological events provided favourable conditions for the establishment of autopolyploids, with the wider distribution of tetraploids of T. sidoides being the result of their range expansion. Key words: cytogeography, establishment, origin, polyploidy, unreduced gametes
The genus Cardionema (Caryophyllaceae) is native to the New World and it comprises six species of perennial herbs, with spiny leaves and sepals, membranous stipules and bracts, and reduced petals. This study aims to update the richness, morphology and distribution of Cardionema in Argentina, based on the study of herbarium specimens. Four species of Cardionema are accepted for the Flora of Argentina; a description of each taxon, an identification key, illustrations and pictures, a comparative-morphology based table, and distribution maps are included. Two lectotypes are also designated.
Most Neotropical Malpighiaceae species are characterized by having zygomorphic flowers and oil glands in the sepals called elaiophores; these floral characteristics are associated with a particular pollination syndrome through oil-collecting bees. This work proposes a study about the structural characteristics of elaiophores in 18 species of Malpighiaceae present in Argentina. The main objectives are to describe the morphology and anatomy of the elaiophores, to detect variation in the number of glands, to compare similarities or differences in elaiophores of species belonging to different lineages, and to know about the potential pollinators and their association with the structural traits of the elaiophores. The morphology and the anatomy were studied using traditional methods of scanning electron and bright-field microscopes. Field trips were carried out to capture oil-collecting bee species on flowers, in different natural populations. Different measurements were taken in the flowers, elaiophores, and oil-collecting bees and were statistically analyzed. Although elaiophores showed a common pattern, some particularities in number, morphology, and anatomy were detected; few of these seem to be restricted to some groups of species phylogenetically related. As regards pollinators, a positive tendency was observed between the size of the flowers, elaiophores, and oil-collecting bees. However, the thickness of the cuticle presented a negative association with the size of the elaiophore and consequently with the floral diameter, which could be presumably related to the foraging behavior and/or the structure of oil-collecting apparatus of the bee species.
Grasses are widespread on every continent and are found in all terrestrial biomes. The dominance and spread of grasses and grassland ecosystems have led to significant changes in Earth’s climate, geochemistry, and biodiversity. The abundance of DNA sequence data, particularly chloroplast sequences, and advances in placing grass fossils within the family allows for a reappraisal of the family's origins, timing, and geographic spread and the factors that have promoted diversification. We reconstructed a time-calibrated grass phylogeny and inferred ancestral areas using chloroplast DNA sequences from nearly 90% of extant grass genera. With a few notable exceptions, the phylogeny is well resolved to the subtribal level. The family began to diversify in the Early–Late Cretaceous (crown age of 98.54 Ma) on West Gondwana before the complete split between Africa and South America. Vicariance from the splitting of Gondwana may be responsible for the initial divergence in the family. However, Africa clearly served as the center of origin for much of the early diversification of the family. With this phylogenetic, temporal, and spatial framework, we review the evolution and biogeography of the family with the aim to facilitate the testing of biogeographical hypotheses about its origins, evolutionary tempo, and diversification. The current classification of the family is discussed with an extensive review of the extant diversity and distribution of species, molecular and morphological evidence supporting the current classification scheme, and the evidence informing our understanding of the biogeographical history of the family.
Loasaceae subfam. Loasoideae are a nearly exclusively American plant group with a center of diversity in Peru. Numerous new taxa have been described over the past decades; one of the most striking discoveries was that of the narrowly endemic Xylopodia with the single species Xylopodia klaprothioides in Peru, Dpto. Cajamarca in 1997. Surprisingly, field studies in the past years have resulted in the discovery of material clearly belonging to the same genus in both Bolivia and northern Argentina, approximately 1500 km SE of the next known population of Xylopodia in Contumazá, Peru. A closer examination shows that Argentinian and Bolivian material belongs to a single species, clearly different from Xylopodia klaprothioides. We here describe Xylopodia laurensis and the entire genus is revised. Both species are illustrated, all aspects of their biology and ecology are portrayed and their threat status is discussed.
Plants belonging to the genera Astragalus, Oxytropis, Ipomoea, Sida and Swainsona often contain the toxin swainsonine (SW), which causes a neurological disorder in livestock. It has been demonstrated that SW is produced by a symbiont fungus associated with these plants. In Ipomoea carnea, the fungus belongs to the ascomycetes of the order Chaetothyriales and grows ectopically on the adaxial surface of leaves. In this study, the presence of the symbiont fungus in different organs of I. carnea is investigated using imaging techniques to understand the process of endophyte transmission. In I. carnea plants with whitish mycelia on the leaf surface, SW could be detected in seeds. Inside the seeds, the mycelium was located on the surface of the cotyledons and on the inner side of the seed coat. We corroborate that the presence of this fungus is a prerequisite for the presence of SW in I. carnea. The demonstration of the localization of the fungus within the seed strongly suggests that this endophyte is vertically transmitted. Our observations verify that the SW-producing fungus in I. carnea is an endosymbiont with epibiotic behavior.
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Information
Address
Larbardén 200, B1642HYD , Darwin, Buenos Aires, Argentina
Head of institution
Fernando O. Zuloaga
Website
www.darwin.edu.ar
Phone
(5411) 4743-4800, 4742-8534, 4747-4748.