Non-invasive determination of plant biomass with microwave resonators

Non-invasive and rapid determination of plant biomass would be beneficial for a number of research aims. Here, we present a novel device to non-invasively determine plant water content as a proxy for plant biomass. It is based on changes of dielectric properties inside a microwave cavity resonator induced by inserted plant material. The water content of inserted shoots leads to a discrete shift in the centre frequency of the resonator. Calibration measurements with pure water showed good spatial homogeneity in the detection volume of the microwave resonators and clear correlations between water content and centre frequency shift. For cut tomato and tobacco shoots, linear correlations between fresh weight and centre frequency shift were established. These correlations were used to continuously monitor diel growth patterns of intact plants and to determine biomass increase over several days. Interferences from soil and root water were excluded by shielding pots with copper. The presented proof of principle shows that microwave resonators are promising tools to quantitatively detect the water content of plants and to determine plant biomass. As the method is non-invasive, integrative and fast, it provides the opportunity for detailed, dynamic analyses of plant growth, water status and phenotype.     

Identification of vegetation and soil carbon pools out of equilibrium in a process model via eddy covariance and biometric constraints

Assumptions of steady‐state conditions in biogeochemical modelling are often invoked because knowledge on the development status of the modelling domain is generally unavailable. Here, we investigate the role of vegetation pool sizes on nonequilibrium conditions through model‐data integration approaches for a set of sites using eddy covariance CO₂ flux data. The study is based on the Carnegie–Ames–Stanford Approach (CASA) model, modified (CASA_G) in order to evaluate the sensitivity of simulated net ecosystem production (NEP) fluxes to vegetation pool sizes. The experimental design is based on the inverse model optimization of different parameter vectors performed at the measurement site level. Each parameter vector prescribes different simulation dynamics that embody different model structural assumptions concerning (non)steady‐state conditions in vegetation and soil carbon pools. We further explore the potential of assimilating biometric constraints through the cost function for sites where in situ information on aboveground biomass or wood pools is available. The integration of biometric data yields marked improvements in the simulation of vegetation C pools compared to single constraints with eddy flux data. Overall, it is necessary to relax both vegetation and soil carbon pools for consistency with the observed data streams. Multiple constraints approaches also leads to variable model performance among the different experimental setups and model structures. We identify and assess the limitations of various model structures and the role of multiple constraints approaches for tackling issues of equifinality. These studies emphasize the need for establishing consistent data sets of fluxes and biometric data for successful model‐data fusion.     

Genetic variation of early height growth traits at the xeric limits of Austrocedrus chilensis (Cupressaceae)

The study of the genetic variation of early height growth traits in seedlings helps to predict the possible outcomes of tree populations in the face of climate change. Second‐year height growth of 10 geographically marginal populations of Patagonian cypress (Austrocedrus chilensis (D. Don) Pic. Ser. et Bizzarri) (Cupressaceae) was characterized under greenhouse conditions. Variation among and within an average of 15 open‐pollinated families (comprising 21 seedlings per family) for each population was analysed for six size and timing traits obtained from fitted Boltzmann growth curves. The among‐family and among‐population variances were 4.03% and 2.74% of the total phenotypic variation, while the residual variance was 84.57% on average. Genetic differentiation among populations was low, except for the maximum growth rate (Q_ST = 0.35) and for growth initiation (Q_ST = 1). For most traits, genetic variation and heritability were variable across populations, except for growth initiation, which showed in general null intra‐population levels of genetic variance. Although no direct associations were found between the additive genetic variation and latitude or altitude, the north range of the distribution was more variable for the pool of the analysed traits. Although most extreme‐marginal populations of A. chilensis would be very limited in their ability to evolve if climate in north‐west Patagonia turns drier and warmer, their long‐term persistence could largely rely on a phenotypic diversification strategy.     

Cuticular lipid diversification in Lasiommata megera and Lasiommata paramegaera: the influence of species, sex, and population (Lepidoptera: Nymphalidae)

Numerous studies have investigated the presence and the effectiveness of volatile pheromones in Lepidoptera. Conversely, very few studies have focused on the composition and the perception of the relatively low volatile components of cuticular mixtures. Yet, cuticular lipids are implied in the recognition processes of several solitary and social insects. In the present study, the cuticular signatures of the satyrid butterflies Lasiommata megera and Lasiommata paramegaera were examined by gas chromatography. General linear model and discriminant analyses on chemical data clearly revealed large differences between sexes, which showed the same diversification pattern in both species. Moreover, a strong diversification between the two species was found, as were differences among populations. These results represent a first step in demonstrating the communicative function of cuticular compounds in the L. megera / paramegaera complex. Moreover, the discrimination among different species and populations on the basis of cuticular mixtures could represent a platform for studying chemotaxonomy and chemical biogeography in butterflies, as already found in several other insect groups.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 703–710.     

A NEW DERCETID FISH (NEOTELEOSTEI: AULOPIFORMES) FROM THE TURONIAN OF THE PELOTAS BASIN, SOUTHERN BRAZIL

Abstract:  Dercetid fishes are common in Tethyan marine deposits of Europe, Asia and Africa. In this paper, we describe a South American dercetid fish, Brazilodercetis longirostris gen. et sp. nov., based on juvenile and adult specimens found in core samples at c. 4000 m sediment depth in the Atlântida Formation (Pelotas Basin, southern Brazil). Brazilodercetis longirostris is a slender, elongate fish recognized on the basis of the following features: prominent snout; contact between mesethmoid and frontals very anterior to the orbit; mesethmoid separating the premaxillae for half of their length; juvenile specimens bearing wedge-like teeth on the anterior third of maxilla; long and shallow crest crossing epioccipital, parietal and posterior border of frontal; a pipe-like preopercle; and reduced neural spine at the middle point of neural arch. Brazilodercetis shares a number of features with the other dercetids, including a pointed snout that is longer than the lower jaw (with Rhynchodercetis and Hastichthys ), a medioparietal skull roof (with Cyranichthys and Benthesikyme ), an unroofed posttemporal fossa (with Dercetoides , Rhynchodercetis and Pelargorhynchus ), a flange on the anguloarticular (with Dercetoides , Hastichthys , Rhynchodercetis and Cyranichthys ), untoothed premaxillae (with Hastichthys and probably Rhynchodercetis ), and a single row of teeth on the maxillae (with Dercetis , Benthesikyme , Rhynchodercetis , Pelargorhynchus , Dercetoides and Hastichthys ).     

El Niño events,the lean versus fat scenario,and long‐term guild dynamics of vertebrate predators in a South American semiarid ecosystem

Abstract Predator assemblages are complex systems in which asynchrony in the dynamics of resources and consumers, and the idiosyncratic perception of environmental conditions by the predators may obscure the detection of expected patterns. We disentangle the specific effects of these variables on the guild structure of a vertebrate predatory assemblage in a semiarid ecosystem of western South America. Over 16 years, this system faced dramatic fluctuations in prey availability associated with four El Niño events. After controlling for other sources of variation, we tested if increased resource availability is associated with higher niche overlaps, as expected from the lean/fat scenario. We determined the existence of two trophic guilds of predators (specialized mammal‐eaters and omnivorous species with emphasis on arthropods) and found that they responded to increased productivity both at the guild and whole assemblage levels. However, the population response of arthropod prey (almost simultaneous) and of different small mammal prey (delayed by 1 or 2 years) to productivity imposed a degree of asynchrony in prey availability and in the response of predators. This resulted in the between‐guilds exchange of predator species depending on mammal prey scarcity or abundance. As a consequence, the observed pattern was an apparent lack of response at the assemblage level. Despite differences in the perception of prey levels by predators, we conclude that each one of them responded accordingly to theoretical predictions following a simple rule: if prey resources are not limiting, predators behave opportunistically converging over the most abundant resources, thus increasing niche overlap; if prey shortages occur, predators specialize on those prey resources that they gather most efficiently, thus lowering niche overlap; if resources become even scarcer, all predators converge again upon the few prey resources still available, thus increasing overlap – out of necessity.     

Checklist and one new species of Bromeliaceae from Pico do Itambé, Minas Gerais,Brazil

A checklist of the 11 genera and 16 species of Bromeliaceae from the Parque Estadual do Pico do Itambé in Santo Antônio do Itambé and Serra Azul de Minas, Minas Gerais, south‐eastern Brazil, is presented. Bromelioideae is the most diverse subfamily and is concentrated in forested areas. Tillandsioideae and Pitcairnioideae are most abundant in elevated areas of campo rupestre vegetation. Vriesea medusa Versieux, a new night‐blooming species belonging to section Xiphion (E.Morren) E.Morren ex Mez, was found in the area and is described and illustrated. It appears to be an endemic species distinguished from Vriesea nanuzae Leme by a combination of the usually larger dimensions in the rosette, the curved inflorescence which has lateral peduncles bearing up to five sterile bracts, the larger number of flowers, floral bracts and sepals that become dark purplish‐brown towards the apex and the coloration of the leaves. Dyckia glandulosa L.B.Sm. & Reitz and Vriesea densiflora Mez, previously poorly known, were rediscovered and are depicted in their habitat for the first time. Vriesea procera var. tenuis L.B.Sm. is a new record for the state. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 709–715.     

International NeuroAIDS: prospects of HIV-1 associated neurological com-plications

INTRODUCTION AND NEUROEPIDEMIO- LOGY OF HIV/AIDS AIDS was first recognized as a new and distinct clini- cal entity in 1981 [1] and the HIV-1 as their casual agent in 1983 [2]. Since then, the HIV/AIDS epidemic has reached epidemic proportions with a total accumulative number of more than 60 million people, according to the Joint United Nations Programme on HIV/AIDS (UNAIDS) and WHO. The extensive spread of HIV-1 epidemics in Asia was not appreciated in the 1980s,…     

Commentary on “Prevalence and evolution of drug resistance HIV-1 variants in Henan, China“

Critical to the implementation and scale-up of successful antiretroviral therapy worldwide is an understanding of the efficacy, toxicities and durability of antiretroviral regimens in the specific populations, which they are utilized. In order to obtain this information monitoring and evaluation or operational research must be done in each country or population.The article by Li et al in this issue represents an outstanding example of the importance of data obtained in the populations treated [1].……