The omnivorous triggerfish Melichthys niger is a functional herbivore on an isolated Atlantic oceanic island

This study evaluated the functional role of the highly generalist omnivore Melichthys niger in the remote St. Peter and St Paul's Archipelago (SPSPA), Brazil, where grazing herbivorous fishes are very scarce. We analysed patterns of distribution from zero to 30 m deep during three time intervals during the day and sampled different aspects of their feeding behaviour, including diel feeding rate, feeding substrate and diet. The density of M. niger increased with depth (26–30 m) and decreased by the end of the day. Although M. niger did not present a typical herbivore diel feeding pattern, they targeted the epilithic algal matrix as their primary feeding substrate, ingesting predominantly algae and detritus. The characteristic Caulerpa racemosa var. peltata from SPSPA was ingested only as detached fronds. We suggest that in the isolated SPSPA, the single species M. niger may perform a unique role as a link between benthic primary production and higher levels. Further studies on the trophic ecology of omnivorous species are necessary to better understand their roles in a reef system, especially in impoverished areas where they are likely to play a crucial role.     

A field portable method for the semi‐quantitative estimation of dehydration tolerance of photosynthetic tissues across distantly related land plants

Desiccation tolerant (DT) plants withstand complete cellular dehydration, reaching relative water contents (RWC) below 30% in their photosynthetic tissues. Desiccation sensitive (DS) plants exhibit different degrees of dehydration tolerance (DHT), never surviving water loss >70%. To date, no procedure for the quantitative evaluation of DHT extent exists that is able to discriminate DS species with differing degrees of DHT from truly DT plants. We developed a simple, feasible and portable protocol to differentiate between DT and different degrees of DHT in the photosynthetic tissues of seed plants and between fast desiccation (< 24 h) tolerant (FDT) and sensitive (FDS) bryophytes. The protocol is based on (1) controlled desiccation inside Falcon tubes equilibrated at three different relative humidities that, consequently, induce three different speeds and extents of dehydration and (2) an evaluation of the average percentage of maximal photochemical efficiency of PSII (F_v/fm) recovery after rehydration. Applying the method to 10 bryophytes and 28 tracheophytes from various locations, we found that (1) imbibition of absorbent material with concentrated salt‐solutions inside the tubes provides stable relative humidity and avoids direct contact with samples; (2) for 50 ml capacity tubes, the optimal plant amount is 50–200 mg fresh weight; (3) the method is useful in remote locations due to minimal instrumental requirements; and (4) a threshold of 30% recovery of the initial F_v/fm upon reaching RWC ≤ 30% correctly categorises DT species, with three exceptions: two poikilochlorophyllous species and one gymnosperm. The protocol provides a semi‐quantitative expression of DHT that facilitates comparisons of species with different morpho‐physiological traits and/or ecological attributes.     

Phosphorus–zinc interactions in cotton: consequences for biomass production and nutrient‐use efficiency in photosynthesis

The fragmentary information on phosphorus (P) × zinc (Zn) interactions in plants warrants further study, particularly in plants known for their high P and Zn requirements, such as cotton (Gossypium hirsutum L.). The objective of this study was to investigate the effect of P × Zn interactions in a modern cultivar of cotton grown hydroponically. Biomass, mineral nutrition and photosynthetic parameters were monitored in plants receiving contrasting combinations of P and Zn supply. Root biomass, length and surface area were similar in plants with low P and/or low Zn supply to those in plants grown with high P and high Zn supply, reflecting an increased root/shoot biomass quotient when plants lack sufficient P or Zn for growth. Increasing P supply and reducing Zn supply increased shoot P concentrations, whilst shoot Zn concentrations were influenced largely by Zn supply. A balanced P × Zn supply (4 mM P × 4 μM Zn) enabled greatest biomass accumulation, while an imbalanced supply of these nutrients led to Zn deficiency, P toxicity or Zn toxicity. Net photosynthetic rate, stomatal conductance, transpiration rate and instantaneous carboxylation efficiency increased as P or Zn supply increased. Although increasing P supply reduced the P‐use efficiency in photosynthesis (PUEP) and increasing Zn supply reduced the Zn‐use efficiency in photosynthesis (ZnUEP), increasing Zn supply at a given P supply increased PUEP and increasing P supply at a given Zn supply increased ZnUEP. These results suggest that agricultural management strategies should seek for balanced mineral nutrition to optimize yields and resource‐use efficiencies.     

Phenotypic plasticity to photon flux density of physiological,anatomical and growth traits in a modern Criollo cocoa clone

Cocoa grows under shade, but some cultivars develop successfully in full sunlight. In order to characterize the response to photosynthetic photon flux density (PPFD) of a Modern Criollo cocoa clone, gas exchange, photochemical activity and leaf traits, and their relation to growth were measured in seedlings growing in a greenhouse at three different values of PPFD, as well as in adults in full sunlight and shade in the field. Plants showed changes in physiological, biochemical, and morpho‐anatomical traits in response to the different light conditions, and in the phenotypic plasticity of these variables. Seedlings subjected to high PPFD in the greenhouse showed decreases in photosynthetic rate, apparent quantum yield of CO₂ fixation and photochemical quenching, and increases in non‐photochemical quenching, suggesting down‐regulation of PSII. In contrast, trees under full sunlight in the field showed a marked reduction in maximum quantum yield of PSII, indicating photoinhibition and supporting that cocoa is a shade tolerant crop. Cocoa showed higher plasticity of physiological and biochemical variables than morpho‐anatomical variables in response to PPFD. Effects of time under treatment in the greenhouse and plant age (greenhouse vs field) on plasticity were observed. The acclimation observed in some of the variables studied after 6 months in high light did not represent a particular advantage to seedlings, since relative growth rate was lower than in low‐ and medium‐light seedlings.     

Spontaneous meningoencephalitis by Staphylococcus aureus in an infant golden‐headed lion tamarin (Leontopithecus chrysomelas)

Non‐human primates are susceptible to many bacteria, some of which bear zoonotic potential. We report the pathologic features of spontaneous fulminating meningoencephalitis by Staphylococcus aureus in a captive infant golden‐headed lion tamarin (Leontopithecus chrysomelas) from Brazil.     

Description of a new Brazilian species of Mycodrosophila (Diptera,Drosophilidae) with emphasis on the morphology of phallic sclerites

Mycodrosophila is a cosmopolitan genus of Drosophilidae that comprises approximately 130 species with mycophagous habitats. In this study, we described a new species of Mycodrosophila based on morphological traits and included details of the male terminalia. The holotype is from Eugênio Lefévre, locality in Campos do Jordão municipality, SP, Brazil, located in the Atlantic rainforest biome and was sampled in the 1930s.     

Soil carbonate drives local adaptation in Arabidopsis thaliana

High soil carbonate limits crop performance especially in semiarid or arid climates. To understand how plants adapt to such soils, we explored natural variation in tolerance to soil carbonate in small local populations (demes) of Arabidopsis thaliana growing on soils differing in carbonate content. Reciprocal field‐based transplants on soils with elevated carbonate (+C) and without carbonate (?C) over several years revealed that demes native to (+C) soils showed higher fitness than those native to (?C) soils when both were grown together on carbonate‐rich soil. This supports the role of soil carbonate as a driving factor for local adaptation. Analyses of contrasting demes revealed key mechanisms associated with these fitness differences. Under controlled conditions, plants from the tolerant deme A1_(+C) native to (+C) soil were more resistant to both elevated carbonate and iron deficiency than plants from the sensitive T6_(?C) deme native to (?C) soil. Resistance of A1_(+C) to elevated carbonate was associated with higher root extrusion of both protons and coumarin‐type phenolics. Tolerant A1_(+C) also had better Ca‐exclusion than sensitive T6_(?C). We conclude that Arabidopsis demes are locally adapted in their native habitat to soils with moderately elevated carbonate. This adaptation is associated with both enhanced iron acquisition and calcium exclusion.