COMMUNITY STUDIES IN POLLINATION ECOLOGY IN THE HIGH TEMPERATE ANDES OF CENTRAL CHILE. I. POLLINATION MECHANISMS AND ALTITUDINAL VARIATION

Pollination mechanisms and pollinators are reported for a total of 137 species (75% of the non-abiotically pollinated flora) as they occur at three altitudinal levels (subandean scrub: 2,200–2,600 m; cushion-plant zone: 2,700–3,100 m; subnival feldfield: 3,200–3,600 m) in the Andean (alpine) zone on the Cordon del Cepo (33°17'S) in central Chile as part of community oriented research in reproductive biology in the high temperate Andes of South America. Only around 4% of the species studied failed to be visited by potential pollinators. Hymenopterans (principally bees) are important pollinators of 50% of the biotically pollinated flora, butterflies of 24% and flies of 46%. Other vectors include beetles, moths, and hummingbirds. An estimated 17% of the flora is anemophilous. Bee species-richness, specialist feeding, and melittophily reach maxima in the subandean scrub; thereafter, bees diminish rapidly in number, with bees pollinating only 13% of the subnival flora as contrasted with 68% of the subandean flora. Although fly and butterfly species-richness also decline with increasing altitude, the proportions of species pollinated by these vectors actually increases. High-altitude populations of melittophilous species with broad altitudinal ranges are invariably serviced by fewer bee species as compared with lower populations. The rich bee fauna at the lower end of the Andean zone in central Chile appears to have resulted from upward colonization from that of the subtending lowland Mediterranean sclerophyllous woodland vegetation. Altitudinal variation in pollination spectra is discussed in relation to contrasting life history characteristics and different modes of thermoregulation in the insect groups involved.     

A protein kinase gene complements the lytic phenotype of Saccharomyces cerevisiae lyt2 mutants

By genetic analysis of a thermosensitive autolytic mutant whose phenotype was complemented by osmotic stabilization with sorbitol, we identified gene LYT2 of Saccharomyces cerevisiae, which is probably involved in cell wall formation. A yeast gene complementing lyt2 strains was cloned and shown to carry an open reading frame coding for a 484-amino-acid protein exhibiting all the characteristic domains of serine/threonine protein kinases and highly homologous to other yeast protein kinases involved in control of the mitotic cycle. Mutants disrupted in the cloned gene also displayed an autolytic phenotype complemented by osmotic stabilization with sorbitol. However, genetic comparison of lyt2 mutants and disruptants of the protein kinase gene revealed that the cloned gene is not the structural gene LYT2 but a suppressor of the lytic phenotype, named gene SLT2, that was mapped to chromosome V. The product of gene SLT2 is the first protein kinase to be described in relation to the yeast cell-wall functions.     

Breeding systems in a montane tropical cloud forest in Venezuela

The breeding systems, reproductive efficacies and population densities of 75 species of trees, shrubs, perennial herbs and vines in a montane tropical cloud forest in Venezuela are investigated. 56.96% and 44.32% of the trees, versus the other life forms considered, respectively possess obligate outbreeding mechanisms. Two shrubs are non-pseudogamous apomicts. The percentage of dioecy among tree species (31%) is among the highest recorded in tropical forests. Reproductive efficacy is similar under all breeding systems in the forest interior. Obligately outbred taxa are slower recolonizers of a disturbed border as compared with non-obligate outbreeders. Explanations are advanced for the high incidence of dioecy combined with a low level of self-incompatibility among hermaphroditic species. It is concluded that the breeding system spectrum reflects an unpredictable pollination pattern, rather than insufficient pollinator servicing.     

Cytological aberrations produced by methotrexate in mouse ascites tumours

The cytological effects have been studied of methotrexate administered in single doses on a hypertriploid ascites tumour in the mouse, which seems to be sensitive to this drug. The drug produced almost total stoppage of the mitotic index, which was maintained for 50 h after administration. The occurrence of fractures in both chromosomes and chromatids in metaphase was the most frequently observed anomaly, sometimes reaching an incidence of 100%. Chromosomal bridges were found in the anaphase in up to 60% of the cells.     

Characteristics of patients with atrial fibrillation prescribed edoxaban in Belgium and the Netherlands: insights from the ETNA-AF-Europe study

BackgroundStudies on the use of non-vitamin K antagonist oral anticoagulants in unselected patients with atrial fibrillation (AF) show that clinical characteristics and dosing practices differ per region, but lack data on edoxaban.MethodsWith data from Edoxaban Treatment in routiNe clinical prActice for patients with AF in Europe (ETNA-AF-Europe), a large prospective observational study, we compared clinical characteristics (including the dose reduction criteria for edoxaban: creatinine clearance 15–50 ml/min, weight ≤60 kg, and/or use of strong p‑glycoprotein inhibitors) of patients from Belgium and the Netherlands (BeNe) with those from other European countries (OEC).ResultsOf all 13,639 patients in ETNA-AF-Europe, 2579 were from BeNe. BeNe patients were younger than OEC patients (mean age: 72.3 vs 73.9 years), and had lower CHA₂DS₂-VASc (mean: 2.8 vs 3.2) and HAS-BLED scores (mean: 2.4 vs 2.6). Patients from BeNe less often had hypertension (61.6% vs 80.4%), and/or diabetes mellitus (17.3% vs 23.1%) than patients from OEC. Moreover, relatively fewer patients in BeNe were prescribed the reduced dose of 30 mg edoxaban (14.8%) than in OEC (25.4%). Overall, edoxaban was dosed according to label in 83.1% of patients. Yet, 30 mg edoxaban was prescribed in the absence of any dose reduction criteria in 36.9% of 30 mg users (5.5% of all patients) in BeNe compared with 35.5% (9.0% of all patients) in OEC.ConclusionThere were several notable differences between BeNe and OEC regarding clinical characteristics and dosing practices in patients prescribed edoxaban, which are relevant for the local implementation of dose evaluation and optimisation.Trial registration{"type":"clinical-trial","attrs":{"text":"NCT02944019","term_id":"NCT02944019"}}NCT02944019; Date of registration 24 October 2016Electronic supplementary materialThe online version of this article (10.1007/s12471-020-01518-7) contains supplementary material, which is available to authorized users.     

Floral nectary structure and nectar composition in Eccremocarpus scaber (Bignoniaceae), a hummingbird-pollinated plant of central Chile

Surface features, anatomy, and ultrastructure of the floral nectary of Eccremocarpus scaber (Bignoniaceae), pollinated predominantly by the largest-known hummingbird (Patagona gigas gigas), were studied together with nectar sugar content and secretion rate. The annular disk nectary comprises epidermis, secretory and ground parenchyma with intercellular spaces, and branched vascular bundles terminating in the secretory parenchyma where only phloem is found. Amyloplasts and vacuoles increase in size throughout development, the latter becoming sites of organelle degradation. Transferlike cells in nectary phloem and P-proteinlike fibrillar material in phloem parenchyma were observed. Flowers produced around 32 μl of nectar (mostly after anthesis) with 11 mg of sugar composed of fructose, glucose, sucrose, and maltose in a ratio of 0.34:0.32:0.17:0.17. Morphological studies as well as the presence of maltose and glucose in nectar suggest storage of the originally phloem-derived sugars as starch with its subsequent hydrolysis. The low sucrose/hexose ratio (0.25) and high nectary secretion force (nectar per flower biomass) observed places E. scaber close to large-bodied bat-pollinated plants. A hypothesis based on nectar origin and nectar secretion is advanced to explain pollinator-correlated variation in sucrose/hexose ratio.     

How well do single samples reflect rotifer species diversity? A test based on interannual variation of rotifer communities in Big Bend National Park (Texas,USA)

Studies of rotifer community composition and dynamics often rely on limited sampling regimes. To determine how well species richness is reflected in these studies, we examined interannual variation of rotifer species richness and monogonont community structure from 10 aquatic systems comprising four habitat types—springs, rock pools (tinajas), former cattle tanks, and artificial ponds—in Big Bend National Park (Texas, USA). Planktonic, littoral, and benthic samples were collected from all sites at about the same date for each of five summers (2001–2005). Our survey yielded 15 monogonont families including 30 genera and 84 species. Two bdelloid taxa also were designated. Species richness varied widely among these four habitats: range, 1–32; mean (±1 SD), 11.2 ± 8.0. Total Species richness in the habitats also varied considerably: springs (54 taxa) > artificial ponds (35 taxa) > tinajas (19 taxa) > cattle tanks (15 taxa). Sessile species comprised ≈13% of the taxa in our samples. Species turnover indices (STI) of these systems indicate low overall relatedness: mean (±1 S.D.) = 85.2 ± 7.1%. The relative frequency of encounter of most taxa in the four systems was low, with 79 taxa (≈92%) having values ≤2.0%. Singleton rates were quite high, ranging from 46.7 to 71.4%, with an overall mean ≈65.1%. Most importantly, we found that both species richness and STI varied considerably among habitat type. Species richness varied by 2–10× between consecutive years and STI ranged from 64 to 89% over the entire study. Our results indicate that rotifer community composition fluctuates greatly over time, and that rotifer community structure may be more labile than is generally believed. Species richness and thus biodiversity may be dramatically underestimated using single sampling or short-term strategies that are often employed in studies of zooplankton community structure. Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont & R. Rico-Martínez Advances in Rotifer Research     

A cypovirus from the South American oil-palm pest Norape argyrrhorea and its potential as a microbial control agent

Norape argyrrhorea, Hubner (Lep.:Megalopygidae), is becoming the most importantdefoliator for oil-palm plantations in Peru(South America). Apart from direct damage,feeding of the larvae also causes wounds thatprovide sites for entry for a complex ofphytopathogenic fungi. Chemical control of N. argyrrhorea is costly and results in theparallel reduction of the populations ofseveral predator and parasitoid insect speciesthat previously limited proliferation of thispest. For this reason, alternative controlmethods are being investigated. Apreviously undescribed occluded virus has beenfound responsible for fast and massivemortality among wild populations of the pest.Based on morphology, protein analysis andnucleic acids, this virus named NoarCPV,belongs to the family Reoviridae. Results ofthe first applications of NoarCPV in anoil-palm plantation demonstrated rapidmortality to population densities below damagethresholds.     

Distribution and δ 13C Values of Portulacaceae Species of the High Andes in Northern Chile

The distribution of species of Portulacaceae in the northern Andes of Chile was recorded during the late growing season along altitudinal transects from 1500 m up to the vegetation limit. The transects were located towards the east of the towns of Arica (18 °S) and Vallenar (28 °S). Whole plants were analysed for δ ¹³C values to examine the occurrence of different photosynthetic pathways. Three species of Calandrinia (C. thyrsoidea, C. spicata and C. grandiflora) and two species of Philippiamra (P. amaranthoides and P. celosioides) were found to have δ ¹³C values indicative of CAM. Portulaca philippi was the only C4 plant in the sample. The CAM species tend to occupy the lower altitudinal levels, which are also relatively drier. All the C3 species occur in the Andean belt, with more favourable water supply. Their δ ¹³C values averaged ?25.1 ‰, a value significantly lower than the average of lowland C3 Calandrinia species reported elsewhere or the general average for lowland C3 plants of ?28.8 ‰. CAM species are also limited to the western slope of the Andean range, while C3 species occur at both sides, but often have discontinuous distributions north or south of the driest section of the Andes (21–24 °S) indicating that their migration along the western side has probably been prevented by extreme aridity. The C3 species occurring on both sides of the aridity barrier are also annual in habit.