Niche filling slows the diversification of Himalayan songbirds.

Speciation generally involves a three-step process--range expansion, range fragmentation and the development of reproductive isolation between spatially separated populations. Speciation relies on cycling through these three steps and each may limit the rate at which new species form. We estimate phylogenetic relationships among all Himalayan songbirds to ask whether the development of reproductive isolation and ecological competition, both factors that limit range expansions, set an ultimate limit on speciation. Based on a phylogeny for all 358 species distributed along the eastern elevational gradient, here we show that body size and shape differences evolved early in the radiation, with the elevational band occupied by a species evolving later. These results are consistent with competition for niche space limiting species accumulation. Even the elevation dimension seems to be approaching ecological saturation, because the closest relatives both inside the assemblage and elsewhere in the Himalayas are on average separated by more than five million years, which is longer than it generally takes for reproductive isolation to be completed; also, elevational distributions are well explained by resource availability, notably the abundance of arthropods, and not by differences in diversification rates in different elevational zones. Our results imply that speciation rate is ultimately set by niche filling (that is, ecological competition for resources), rather than by the rate of acquisition of reproductive isolation.

Determinants of northerly range limits along the Himalayan bird diversity gradient.

The primary explanation for the latitudinal gradient in species diversity must lie in why species fail to expand ranges across different climatic regimes. Theories of species gradients based in niche conservatism assume that whole clades are confined to particular climatic regimes because the traits they share limit adaptation to alternative regimes. We assess these theories in an analysis of the twofold decline in bird species richness along the Himalayas from the southeast to the northwest. The presence of fewer species in the northwest is entirely due to a steep decline in the number of forest species; species occupying more open habitats show a reversed gradient. Forest species numbers are exceptionally high at midelevations (1,000-2,000 m) in the southeast, which experience a warm, wet climate not present in the northwest, and a high proportion of these species fail to expand their range to the northwest. Despite this, many species do have populations or close relatives that straddle different climatic regimes along altitudinal gradients and/or the regional gradient, implying that climate-based niche conservatism per se does not strongly constrain range limits. We argue that climate- and competition-mediated resource distributions are important in setting northerly range limits and show that one measure of forest resources (foliage density) is lower in the northwest.

Efficient design of multituned transmission line NMR probes: the electrical engineering approach.

Transmission line-based multi-channel solid state NMR probes have many advantages regarding the cost of construction, number of RF-channels, and achievable RF-power levels. Nevertheless, these probes are only rarely employed in solid state-NMR-labs, mainly owing to the difficult experimental determination of the necessary RF-parameters. Here, the efficient design of multi-channel solid state MAS-NMR probes employing transmission line theory and modern techniques of electrical engineering is presented. As technical realization a five-channel ((1)H, (31)P, (13)C, (2)H and (15)N) probe for operation at 7 Tesla is described. This very cost efficient design goal is a multi port single coil transmission line probe based on the design developed by Schaefer and McKay. The electrical performance of the probe is determined by measuring of Scattering matrix parameters (S-parameters) in particular input/output ports. These parameters are compared to the calculated parameters of the design employing the S-matrix formalism. It is shown that the S-matrix formalism provides an excellent tool for examination of transmission line probes and thus the tool for a rational design of these probes. On the other hand, the resulting design provides excellent electrical performance. From a point of view of Nuclear Magnetic Resonance (NMR), calibration spectra of particular ports (channels) are of great importance. The estimation of the π/2 pulses length for all five NMR channels is presented.

Chemical synthesis of membrane proteins: a model study on the influenza virus B proton channel.

In the present study we have developed and optimized a robust strategy for the synthesis of highly hydrophobic peptides, especially membrane proteins, exemplarily using the influenza B M2 proton channel (BM2(1-51)). This strategy is based on the native chemical ligation of two fragments, where the thioester fragment is formed from an oxo-ester peptide, which is synthesized using Fmoc-SPPS, and features an in situ cleavable solubilizing tag (ADO, ADO2 or ADO-Lys5). The nearly quantitative production of the ligation product was followed by an optimized work up protocol, resulting in almost quantitative desulfurization and Acm-group cleavage. Circular dichroism analysis in a POPC lipid membrane revealed that the synthetic BM2(1-51) construct adopts a helical structure similar to that of the previously characterized BM2(1-33).

Body composition, energy utilization, and nitrogen metabolism with a severely restricted diet supplemented with dihydroxyacetone and pyruvate.

To determine the effect of dietary modification on energy utilization during severely restrictive hypocaloric feeding, we measured body composition, energy deficit, and nitrogen metabolism in 13 obese women housed in a metabolic ward consuming a 2.1-MJ diet for 21 d with the three-carbon compounds dihydroxyacetone and pyruvate (DHAP), partially, isocalorically substituted for glucose. Body composition and amino acid (leucine) oxidation and turnover were determined before and after weight loss. Energy deficit was calculated from metabolic rates and compared with weight and fat loss. Subjects fed dihydroxyacetone and pyruvate showed a greater weight loss (DHAP = 6.5 +/- 0.3 kg, P = 5.6 +/- 0.2 kg), fat loss (DHAP = 4.3 +/- 0.2 kg, P = 3.5 +/- 0.1 kg), and weight and fat loss/4.25-MJ deficit (P less than 0.05 for all determinations). Nitrogen balance (urine and stool) and leucine metabolism were similar in both groups. We conclude that partial substitution of DHAP for six-carbon compounds of a 2.1-MJ diet will increase weight and fat loss.

Body composition, energy utilization, and nitrogen metabolism with a 4.25-MJ/d low-energy diet supplemented with pyruvate.

We measured body composition, energy deficit, and nitrogen metabolism in 14 obese women housed in a metabolic ward, who consumed a 4.25-MJ/d liquid diet (68% carbohydrate, 22% protein) for 21 d with or without pyruvate (PY; n = 7) partially, isoenergetically substituted for glucose (placebo; n = 7). Body composition and leucine oxidation and turnover were determined before and after weight loss. Energy deficit was calculated from resting metabolic rates. Subjects fed pyruvate showed a greater weight loss (PY = 5.9 +/- 0.7 kg, placebo = 4.3 +/- 0.3 kg, P less than 0.05), fat loss (PY = 4.0 +/- 0.5 kg, placebo = 2.7 +/- 0.2 kg, P less than 0.05), kg wt loss/4.25-MJ deficit (PY = 0.22 +/- 0.01 kg, placebo = 0.17 +/- 0.01 kg, P less than 0.05, and kg fat loss/4.25-MJ deficit (PY = 0.15 +/- 0.01 kg, placebo = 0.11 +/- 0.01 kg, P less than 0.05). Nitrogen balance (urine and stool) and leucine oxidation and turnover were similar in both groups. We conclude that the dietary modification whereby the three-carbon compound pyruvate is isoenergetically substituted for the six-carbon compound glucose in a 4.25-MJ/d, low-energy diet will increase fat and weight loss.

Body composition, nitrogen metabolism, and energy utilization with feeding of mildly restricted (4.2 MJ/d) and severely restricted (2.1 MJ/d) isonitrogenous diets.

To determine the effects on weight loss of feeding isonitrogenous diets in mildly restricted (4.2 MJ/d) and severely restricted (2.1 MJ/d) amounts, we measured body composition, weight loss-energy deficit ratio, and nitrogen metabolism in 14 obese women housed in a metabolic ward consuming hypoenergetic diets for 21 d. Subjects consumed either a 4.2-MJ/d diet (50 g protein, 175 g carbohydrate) or a 2.1-MJ/d diet (50 g protein, 75 g carbohydrate). Body composition and leucine oxidation and turnover were determined before and after weight loss. Energy deficit was calculated from resting metabolic rates. Subjects fed the 2.1-MJ/d diet showed a greater weight loss (6.1 +/- 0.5 vs 4.5 +/- 0.5 kg; mean +/- SE, P less than 0.05) and fat loss (3.9 +/- 0.3 vs 3.0 +/- 0.3 kg, P less than 0.05). Weight loss-energy deficit ratio was the same with both diets. Nitrogen balance and leucine oxidation and turnover were similar in both groups. We conclude that with feeding of isonitrogenous hypoenergetic diets, severe restriction of energy content (2.1 MJ/d, 75 g carbohydrate) will enhance weight and fat loss without increasing nitrogen loss compared with mild restriction of energy (4.2 MJ/d).

Ecological limits on diversification of the Himalayan core Corvoidea.

Within regions, differences in the number of species among clades must be explained by clade age, net diversification rate, or immigration. We examine these alternatives by assessing historical causes of the low diversity of a bird parvorder in the Himalayas (the core Corvoidea, 57 species present), relative to its more species rich sister clade (the Passerida, ∼400 species present), which together comprise the oscine passerines within this region. The core Corvoidea contain ecologically diverse species spanning a large range of body sizes and elevations. Despite this diversity, on the basis of ecological, morphological, and phylogenetic information, we infer that the best explanation for the low number of species within the Himalayan core Corvoidea is one in which ecology limits diversification and/or immigration. Within the core Corvoidea, body size is correlated with elevation: large species are found at high elevations, and small species at lower elevations. This contrasts with the presence of many small-bodied species spanning all elevations in the Passerida and many large bodied species at low elevations in the other orders of birds (the nonpasserines). Cladogenetic events leading to ecological differences between species in body size and shape mostly occurred millions of years ago, and the rate of evolutionary change has declined toward the present. Elevational distributions have been evolutionarily more labile, but are also associated with ancient cladogenetic events. We suggest the core Corvoidea occupy a restricted volume of ecological space in competition with other bird species, and this has limited in situ diversification and/or immigration.