The dependence of respiration on photosynthetic substrate supply and temperature: integrating leaf, soil and ecosystem measurements

Interactions between photosynthetic substrate supply and temperature in determining the rate of three respiration components (leaf, belowground and ecosystem respiration) were investigated within three environmentally controlled, Populus deltoides forest bays at Biosphere 2, Arizona. Over 2 months, the atmospheric CO₂ concentration and air temperature were manipulated to test the following hypotheses: (1) the responses of the three respiration components to changes in the rate of photosynthesis would differ both in speed and magnitude; (2) the temperature sensitivity of leaf and belowground respiration would increase in response to a rise in substrate availability; and, (3) at the ecosystem level, the ratio of respiration to photosynthesis would be conserved despite week‐to‐week changes in temperature. All three respiration rates responded to the CO₂ concentration‐induced changes in photosynthesis. However, the proportional change in the rate of leaf respiration was more than twice that of belowground respiration and, when photosynthesis was reduced, was also more rapid. The results suggest that aboveground respiration plays a key role in the overall response of ecosystem respiration to short‐term changes in canopy photosynthesis. The short‐term temperature sensitivity of leaf respiration, measured within a single night, was found to be affected more by developmental conditions than photosynthetic substrate availability, as the Q₁₀ was lower in leaves that developed at high CO₂, irrespective of substrate availability. However, the temperature sensitivity of belowground respiration, calculated between periods of differing air temperature, appeared to be positively correlated with photosynthetic substrate availability. At the ecosystem level, respiration and photosynthesis were positively correlated but the relationship was affected by temperature; for a given rate of daytime photosynthesis, the rate of respiration the following night was greater at 25 than 20°C. This result suggests that net ecosystem exchange did not acclimate to temperature changes lasting up to 3 weeks. Overall, the results of this study demonstrate that the three respiration terms differ in their dependence on photosynthesis and that, short‐ and medium‐term changes in temperature may affect net carbon storage in terrestrial ecosystems.     

The energetic importance of terrestrial arthropod inputs to three warm-water streams

1. Inputs of terrestrial arthropods (number and mass m^–2 d^–1) from riparian corridors to three streams representing different orders were highly variable among seasons and sites, with significantly greater ( P < 0.05) inputs at the headwater stream during summer months, compared with other sites and seasons.
2. No significant differences in estimates of stream retention of terrestrial arthropods (number and mass m^–2 d^–1) were observed among sites; however, retention of terrestrial arthropods at all sites was significantly greater during summer months, compared with other periods.
3. The gravimetric proportion of terrestrial arthropods present in the stomachs of redbreast sunfish ( Lepomis auritus ) and bluegill ( L. macrochirus ) was equivalent among sites. However, estimates of the dietary importance of terrestrial arthropods at all study sites were significantly greater in the summer, compared with other seasons.
4. Estimates of the potential annual energetic contribution (kJ m^–2 d^–1) of terrestrial arthropod inputs to the stream system were comparable with published rates of total annual production of aquatic macroinvertebrates in other Virginia headwater streams.
5. Results of this study supported the hypothesis that terrestrial arthropods represented an important energetic subsidy to stream fish during periods of low aquatic macroinvertebrate availability, and suggest that this component of allochthonous input is a potentially significant, but poorly understood energetic linkage between riparian landscapes and stream ecosystems.     

Phytogeny of the nematocerous families of Diptera (insecta)

The relationships of the nematocerous families of Diptera are cladistieally analysed using the parsimony programs PAUP and Hennig86. An extensive review, as well as a data matrix, is presented for 98 almost exclusively morphological characters (larva, 56; pupa, 6; adult, 36). Four infraorders are recognized, viz , Ptychopteromorpha, Culicomorpha, Blephariceromorpha, Bibionomorpha, and a clade containing the 'higher Nematocera' and Brachycera. Traditionally the family Nymphomyiidae or the infraorder Tipulomorpha (=Tipulidae, with or without Trichoceridae) are considered the most basal clade of the extant Diptera. On the basis of our cladistic analysis it is suggested that the Ptychopteromorpha-Culicomorpha clade is the sister-group of all other extant Diptera. We provide evidence that the Axymyiidae are part of a monophyletic Bibionomorpha. The latter infraorder is proposed as the sister-group of the higher Nematocera and Brachycera. We transfer the Tipulidae (Tipulomorpha) to the higher Nematocera, at a position next to Trichoceridae and near the Anisopodidae-Brachycera lineage. Previous hypotheses concerning nematocerous relationships are reviewed.     

Do geographic distribution,niche property and life form explain plants' vulnerability to global change?

We modelled the future distribution in 2050 of 975 endemic plant species in southern Africa distributed among seven life forms, including new methodological insights improving the accuracy and ecological realism of predictions of global changes studies by: (i) using only endemic species as a way to capture the full realized niche of species, (ii) considering the direct impact of human pressure on landscape and biodiversity jointly with climate, and (iii) taking species' migration into account. Our analysis shows important promises for predicting the impacts of climate change in conjunction with land transformation. We have shown that the endemic flora of Southern Africa on average decreases with 41% in species richness among habitats and with 39% on species distribution range for the most optimistic scenario. We also compared the patterns of species' sensitivity with global change across life forms, using ecological and geographic characteristics of species. We demonstrate here that species and life form vulnerability to global changes can be partly explained according to species' (i) geographical distribution along climatic and biogeographic gradients, like climate anomalies, (ii) niche breadth or (iii) proximity to barrier preventing migration. Our results confirm that the sensitivity of a given species to global environmental changes depends upon its geographical distribution and ecological proprieties, and makes it possible to estimate a priori its potential sensitivity to these changes.     

Bridging the Divide: Drinking among Street Drug Users

In this research report, we present findings on drinking among drug users from a larger multimethod study of the public health consequences of emergent, changing, and understudied drug-related behavioral patterns among street drug users in Hartford, CT. Although drinking and illicit drug use traditionally have been studied in anthropology as separate cultural domains, this conceptual division has hindered examination of the significant level of drinking among street drug users, the motivations for heavy drinking in this population, and the public health consequences of mixing alcohol and other drugs, including drug relapse.     

Genomic insights into ayurvedic and western approaches to personalized medicine

Ayurveda, an ancient Indian system of medicine documented and practised since 1500 B.C., follows a systems approach that has interesting parallels with contemporary personalized genomic medicine approaches to the understanding and management of health and disease. It is based on the trisutra, which are the three aspects of causes, features and therapeutics that are interconnected through a common organizing principle termed ‘tridosha’. Tridosha comprise three ascertainable physiological entities; vata (kinetic), pitta (metabolic) and kapha (potential) that are pervasive across systems, work in conjunction with each other, respond to the external environment and maintain homeostasis. Each individual is born with a specific proportion of tridosha that are not only genetically determined but also influenced by the environment during foetal development. Jointly they determine a person’s basic constitution, which is termed their ‘prakriti’. Development and progression of different diseases with their subtypes are thought to depend on the origin and mechanism of perturbation of the doshas, and the aim of therapeutic practice is to ensure that the doshas retain their homeostatic state. Similarly, western systems biology epitomized by translational P4 medicine envisages the integration of multiscalar genetic, cellular, physiological and environmental networks to predict phenotypic outcomes of perturbations. In this perspective article, we aim to outline the shape of a unifying scaffold that may allow the two intellectual traditions to enhance one another. Specifically, we illustrate how a unique integrative ‘Ayurgenomics’ approach can be used to integrate the trisutra concept of Ayurveda with genomics. We observe biochemical and molecular correlates of prakriti and show how these differ significantly in processes that are linked to intermediate patho-phenotypes, known to take different course in diseases. We also observe a significant enrichment of the highly connected hub genes which could explain differences in prakriti, focussing on EGLN1, a key oxygen sensor that differs between prakriti types and is linked to high altitude adaptation. Integrating our observation with the current literature, we demonstrate how EGLN1 could qualify as a molecular equivalent of tridosha that can modulate different phenotypic outcomes, where hypoxia is a cause or a consequence both during health and diseased states. Our studies affirm that integration of the trisutra framework through Ayurgenomics can guide the identification of predisposed groups of individuals and enable discovery of actionable therapeutic points in an individualized manner.     

The Effects of Modifying Sucrose Concentration on the Development of Maize Kernels Grown in vitro

Intact Zea mays L. kernels attached to cob tissue develop tomaturity when grown in vitro. This experiment was designed todetermine if it is possible to prolong kernel growth by refreshingthe culture medium. Blocks of maize kernels were grown in vitroon media containing several concentrations of sucrose. Kernels,at all concentrations of sucrose, developed to maturity at 30–35d post-pollination, indicating that it is not possible to extendthe kernel growth phase by supplying a carbohydrate source.Kernels grown on media containing 80 g 1^–1 or higher sucroseconcentration had a significantly greater percentage of kernelsthat developed to maturity, and had greater weight and starchcontent per seed. Zea mays, kernel culture, seed development, starch     

Endemic species and ecosystem sensitivity to climate change in Namibia

We present a first assessment of the potential impacts of anthropogenic climate change on the endemic flora of Namibia, and on its vegetation structure and function, for a projected climate in ～2050 and ～2080. We used both niche‐based models (NBM) to evaluate the sensitivity of 159 endemic species to climate change (of an original 1020 plant species modeled) and a dynamic global vegetation model (DGVM) to assess the impacts of climate change on vegetation structure and ecosystem functioning. Endemic species modeled by NBM are moderately sensitive to projected climate change. Fewer than 5% are predicted to experience complete range loss by 2080, although more than 47% of the species are expected to be vulnerable (range reduction >30%) by 2080 if they are assumed unable to migrate. Disaggregation of results by life‐form showed distinct patterns. Endemic species of perennial herb, geophyte and tree life‐formsare predicted to be negatively impacted in Namibia, whereas annual herb and succulent endemic species remain relatively stable by 2050 and 2080. Endemic annual herb species are even predicted to extend their range north‐eastward into the tree and shrub savanna with migration, and tolerance of novel substrates. The current protected area network is predicted to meet its mandate by protecting most of the current endemicity in Namibia into the future. Vegetation simulated by DGVM is projected to experience a reduction in cover, net primary productivity and leaf area index throughout much of the country by 2050, with important implications for the faunal component of Namibia's ecosystems, and the agricultural sector. The plant functional type (PFT) composition of the major biomes may be substantially affected by climate change and rising atmospheric CO₂– currently widespread deciduous broad leaved trees and C₄ PFTs decline, with the C₄ PFT particularly negatively affected by rising atmospheric CO₂ impacts by ～2080 and deciduous broad leaved trees more likely directly impacted by drying and warming. The C₃ PFT may increase in prominence in the northwestern quadrant of the country by ～2080 as CO₂ concentrations increase. These results suggest that substantial changes in species diversity, vegetation structure and ecosystem functioning can be expected in Namibia with anticipated climate change, although endemic plant richness may persist in the topographically diverse central escarpment region.     

The phylogenetic relationships among infraorders and superfamilies of Diptera based on morphological evidence

Members of the megadiverse insect order Diptera (flies) have successfully colonized all continents and nearly all habitats. There are more than 154 000 described fly species, representing 10–12% of animal species. Elucidating the phylogenetic relationships of such a large component of global biodiversity is challenging, but significant advances have been made in the last few decades. Since Hennig first discussed the monophyly of major groupings, Diptera has attracted much study, but most researchers have used non‐numerical qualitative methods to assess morphological data. More recently, quantitative phylogenetic methods have been used on both morphological and molecular data. All previous quantitative morphological studies addressed narrower phylogenetic problems, often below the suborder or infraorder level. Here we present the first numerical analysis of phylogenetic relationships of the entire order using a comprehensive morphological character matrix. We scored 371 external and internal morphological characters from larvae, pupae and adults for 42 species, representing all infraorders selected from 42 families. Almost all characters were obtained from previous studies but required revision for this ordinal‐level study, with homology assessed beyond their original formulation and across all infraorders. We found significant support for many major clades (including the Diptera, Culicomorpha, Bibionomorpha, Brachycera, Eremoneura, Cyclorrhapha, Schizophora, Calyptratae and Oestroidea) and we summarize the character evidence for these groups. We found low levels of support for relationships between the infraorders of lower Diptera, lower Brachycera and major lineages of lower Cyclorrhapha, and this is consistent with findings from molecular studies. These poorly supported areas of the tree may be due to periods of rapid radiation that left few synapomorphies in surviving lineages.