bluuebunny/crossref_metadata_2025_split huggingface dataset:
Longer growing seasons lead to less carbon sequestration by a subalpine forest
Authors: HU JIA , MOORE DAVID J. P. , BURNS SEAN P. , MONSON RUSSELL K. 
Published: May 2009

AbstractAs global temperatures increase, the potential for longer growing seasons to enhance the terrestrial carbon sink has been proposed as a mechanism to reduce the rate of further warming. At the Niwot Ridge AmeriFlux site, a subalpine forest in the Colorado Rocky Mountains, we used a 9‐year record (1999–2007) of continuous eddy flux observations to show that longer growing season length (GSL) actually resulted in less annual CO2 uptake. Years with a longer GSL were correlated with a shallower snow pack, as measured using snow water equivalent (SWE). Furthermore, years with a lower SWE correlated with an earlier start of spring. For three years, 2005, 2006, and 2007, we used observations of stable hydrogen isotopes (δD) of snow vs. rain, and extracted xylem water from the three dominant tree species, lodgepole pine, Engelmann spruce, and subalpine fir, to show that the trees relied heavily on snow melt water even late into the growing season. By mid‐August, 57% to 68% of xylem water reflected the isotopic signature of snow melt. By coupling the isotopic water measurements with an ecosystem model, SIPNET, we found that annual forest carbon uptake was highly dependent on snow water, which decreases in abundance during years with longer growing seasons. Once again, for the 3 years 2005, 2006, and 2007, annual gross primary productivity, which was derived as an optimized parameter from the SIPNET model was estimated to be 67% 77%, and 71% dependent on snow melt water, respectively. Past studies have shown that the mean winter snow pack in mountain ecosystems of the Western US has been declining for decades and is correlated with positive winter temperature anomalies. Since climate change models predict continuation of winter warming and reduced snow in mountains of the Western US, the strength of the forest carbon sink is likely to decline further.
Global warming and alternative causes of decline in arctic‐alpine and boreal‐montane lichens in North‐Western Central Europe
Authors: HAUCK MARKUS 
Published: May 2009

AbstractLichens are thought to be sensitive indicators of global warming, as the spread of several thermophilous epiphytes in north‐western Central Europe has been attributed to late 20th century warming. In the present paper, the potential contribution of late 20th century warming to the decline of arctic‐alpine and boreal‐montane lichen species is analyzed. Relevant ecological groups of lichens include terricolous heathland species, saxicolous species of exposed rock outcrops and boulder fields as well as epiphytes of mountain forests. These three groups of lichens experienced significant declines before the onset of late 20th century warming in the 1970s. These declines can be attributed to the abandonment of traditional land use systems in the case of the heathland lichens, increased recreational use of the exposed summits usually inhabited by cold‐tolerant saxicolous lichens, and to high atmospheric SO2 levels in the mid‐20th century, but are probably not directly connected to global warming.
Establishment of Italian ryegrass (Lolium multiflorum Lam.) by self‐seeding as affected by cutting date and degree of herbage removal in spring in pastures of the southern Great Plains of the United States
Authors: Bartholomew P. W. , Williams R. D. 
Published: May 2009

AbstractAnnually sown cool‐season small‐grain cereal species can provide a valuable source of cool‐season herbage for livestock in the southern Great Plains of the USA but limited access to field equipment for cultivation and sowing is an obstacle to their use. Italian ryegrass (Lolium multiflorum Lam.) (IRG) can persist through self‐seeding and may offer an alternative source of cool‐season herbage. The effects of cutting dates in mid‐April, early May or mid‐ to late May following sowing in the previous September, and of removing 0·57, 0·73 or 1·00 of the herbage mass at this time, on subsequent seed deposition, seedling re‐establishment and herbage production of IRG were measured. Later cutting dates reduced seed production, seed deposition, 1000‐seed weight and eventual re‐establishment of IRG seedlings. Removing different proportions of the herbage mass did not compensate for reduced seed deposition arising from later cutting dates. Numbers of seed heads and seed required to achieve a self‐seeded target population of 500 established seedlings m−2 ranged from 885 to 5650 seed heads m−2 and 3360 to 5850 deposited viable seeds m−2. Re‐establishment of IRG through self‐seeding showed a failure rate of 0·43 indicating that self‐seeded IRG will need periodic resowing. Any economic benefit derived from self‐seeded IRG will depend heavily on the success of its rate of re‐establishment.
Fatty acid composition and nutritive value of twelve cultivars of perennial ryegrass
Authors: Palladino R. A. , O’Donovan M. , Kennedy E. , Murphy J. J. , Boland T. M. , Kenny D. A. 
Published: May 2009

AbstractA comparison was made of the fatty acid composition and nutritive value of twelve cultivars of perennial ryegrass (Lolium perenne L.) differing in heading date and ploidy level. The cultivars were sown in triplicate plots and three sequential cuts of herbage were taken at 20‐d intervals during the late spring and early summer to describe the fatty acid composition and other measurements of nutritive value. Differences between cultivars were recorded for DM content (P < 0·01) and concentrations of gross energy, neutral‐detergent fibre (NDF) and ash (P < 0·05). Diploid cultivars had a higher DM content and concentration of NDF (P < 0·01) than tetraploid cultivars whilst late‐heading date cultivars had the lower NDF (P < 0·05), ADF and ash (P < 0·01) concentrations. There was variation between cultivars in fatty acid composition. Diploid cultivars had a higher concentration of C18:0 (P < 0·01) and C18:1 (P < 0·05) than tetraploid cultivars and late‐heading date cultivars had the highest concentrations of total fatty acids, C16:0, C18:2 and C18:3 (P < 0·05). This was predominantly due to the cultivar Tyrella which is a diploid, late‐heading cultivar. The study showed that some variation exists between perennial ryegrass cultivars in concentrations of polyunsaturated fatty acids, which may present opportunities to select for this trait, but further research on the developmental stages and degree of leafiness of cultivars is first required.
Seed production of an Arrhenatherion elatioris hay‐meadow in the eastern Italian Alps
Authors: Scotton M. , Piccinin L. , Dainese M. , Sancin F. 
Published: May 2009

AbstractDue to agricultural intensification, semi‐natural Arrhenatherion elatioris meadows are becoming rare in central Europe. Despite the increasing importance of their biodiversity value, little information is available on seed production which could be used to enlarge their regional presence. To contribute to this knowledge, the seed production of the major grass species were analysed for the spring growths of an Arrhenatherion elatioris meadow in 2003 and 2004. In the first study year, fertile culms of Anthoxanthum odoratum, Arrhenatherum elatius, Avenula pubescens, Dactylis glomerata, Holcus lanatus and Trisetum flavescens were collected on different dates and analysed for their reproductive efficiency. Floret site utilization was greater than 0·60 for all species and seed viability was above 80%, except for A. odoratum. Seed dormancy was present to a small extent only in A. odoratum and A. pubescens. With regard to the whole meadow, the density of fertile stems amounted to 850 m−2 (811 m−2 of which were grasses) and standing seed yield at seed maturity of the six grasses was about 33 100 seeds m−2. As a consequence of the increase in viability occurring during seed development, the maximum standing viable seed yield was reached later. The total number of seeds produced throughout the spring growth period was 2·8 times that of the maximum standing seed yield. The quality and quantity of the seed production from spring growth make it suitable for establishing species‐rich semi‐natural grassland provided that seed obtained from the second cut is included to increase the presence of legumes and forbs.
Predator size, prey size and threshold food densities of diving ducks: does a common prey base support fewer large animals?
Authors: Richman Samantha E. , Lovvorn James R. 
Published: May 2009

Summary 1. Allometry predicts that a given habitat area or common prey biomass supports fewer numbers of larger than smaller predators; however, birds from related taxa or the same feeding guild often deviate from this pattern. In particular, foraging costs of birds may differ among locomotor modes, while intake rates vary with accessibility, handling times and energy content of different‐sized prey. Such mechanisms might affect threshold prey densities needed for energy balance, and thus relative numbers of different‐sized predators in habitats with varying prey patches. 2. We compared the foraging profitability (energy gain minus cost) of two diving ducks: smaller lesser scaup (Aythya affinis, 450–1090 g) and larger white‐winged scoters (Melanitta fusca, 950–1800 g). Calculations were based on past measurements of dive costs with respirometry, and of intake rates of a common bivalve prey ranging in size, energy content and burial depth in sediments. 3. For scaup feeding on small prey <12 mm long, all clams buried deeper than 5 cm were unprofitable at realistic prey densities. For clams buried in the top 5 cm, the profitability threshold decreased from 216 to 34 clams m−2 as energy content increased from 50 to 300 J clam−1. 4. For larger scoters feeding on larger prey 18–24 mm long, foraging was profitable for clams buried deeper than 5 cm, with a threshold density of 147 m−2 for clams containing 380 J clam−1. For clams <5 cm deep, the threshold density decreased from 86 to 36 clams m−2 as energy content increased from 380 to 850 J clam−1. If scoters decreased dive costs by swimming with wings as well as feet (not an option for scaup), threshold prey densities were 11–12% lower. 5. Our results show that threshold densities of total prey numbers for different‐sized ducks depend on prey size structure and depth in the sediments. Thus, heterogeneity in disturbance regimes and prey population dynamics can create a mosaic of patches favouring large or small predators. Whether a given area or total prey biomass will support greater numbers of larger or smaller predators will vary with these effects.
Review of recent genome‐wide association scans in lupus
Authors: Graham R. R. , Hom G. , Ortmann W. , Behrens T. W. 
Published: May 2009

Abstract.We review the systemic lupus erythematosus (SLE) human genetics literature, including the first wave of genome‐wide associations scans (GWAS), to identify confirmed and candidate risk variants that meet stringent statistical criteria. The understanding of the genetic basis of SLE in humans has expanded dramatically over the past year, offering an early glimpse into the primary genetic factors and major dysregulated pathways. A meta‐analysis of published candidate variants was performed incorporating data from a 1310 case and 7859 control GWAS. Our review of the literature and meta‐analysis identifies a total of 17 well‐validated common SLE risk variants, including four candidate variants that achieve our definition of a confirmed SLE risk locus. These variants account for a fraction of the total genetic contribution to SLE risk, with many risk loci remaining to be identified, but may provide insight into the pathways involved in SLE. Initial pathway analyses of the 17 confirmed SLE risk alleles indicate an important role for B‐cell signalling and development, signaling through toll‐like receptors 7 and 9, and neutrophil function.
Th17 cells in rheumatoid arthritis and systemic lupus erythematosus
Authors: Pernis A. B. 
Published: May 2009

Abstract.Recent work has implicated a novel Th effector cell subset, the Th17 cell subset, in the development of both rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) because of the ability of Th17 cells to produce cytokines like IL‐17 and IL‐21 that can drive both inflammatory and humoral responses. In this review, we will discuss recent studies that have begun elucidating the factors that regulate the development of Th17 cells and provide a brief overview of the role of Th17 cells in RA and SLE.
Receptor crosstalk: reprogramming B cell receptor signalling to an alternate pathway results in expression and secretion of the autoimmunity‐associated cytokine, osteopontin
Authors: Rothstein T. L. , Guo B. 
Published: May 2009

Abstract.Intracellular signalling emanating from the B‐cell antigen receptor is considered to follow a discrete course that requires participation by a set of mediators, grouped together as the signalosome, in order for downstream events to occur. Recent work indicates that this paradigm is true only for naïve B cells. Following engagement of the IL‐4 receptor, a new, alternate pathway for B‐cell receptor (BCR)‐triggered intracellular signalling is established that bypasses the need for signalosome elements and operates in parallel with the classical, signalosome‐dependent pathway. Reliance on Lyn and sensitivity to rottlerin by the former, but not the latter, distinguishes these two pathways. The advent of alternate pathway signalling leads to production and secretion by B cells of osteopontin (Opn). As Opn is a polyclonal B‐cell activator that is strongly associated with a number of autoimmune diseases including lupus and rheumatoid arthritis, this novel finding is likely to be clinically relevant. Our results highlight the potential role of B‐cell‐derived Opn in immunity and autoimmunity and suggest that stress‐related IL‐4 expression might act to strengthen immunoglobulin secretion at the risk of autoantibody formation. Further, these results illustrate receptor crosstalk in the form of reprogramming, whereby engagement of one receptor (IL‐4R) produces an effect that persists after the original ligand (IL‐4) is removed and results in alteration of the pathway, and outcome, of signalling via a second receptor (BCR) following its activation.
Lipid lowering versus pleiotropic effects of statins on skin microvascular function in patients with dysglycaemia and coronary artery disease
Authors: Settergren M. , Böhm F. , Rydén L. , Pernow J. , Kalani M. 
Published: May 2009

Abstract.Objectives.  To investigate the impact of lipid lowering therapy by different means on skin microvascular function in patients with dysglycaemia and coronary artery disease (CAD).Design and setting.  Thirty‐six patients were randomized to simvastatin 80 mg daily (S80, n = 19) or ezetimibe 10 mg and simvastatin 10 mg daily (E10/S10, n = 17) for 6 weeks. Skin microvascular function was assessed by laser Doppler fluxmetry (LDF) at rest, following arterial occlusion (peak postocclusive LDF) and following local heating on the forearm (heat arm LDF) and foot (heat foot LDF). LDF parameters and serum lipids were evaluated at baseline and follow‐up.Results.  At follow‐up, LDL cholesterol had decreased from 3.1 (2.7–3.5) to 1.6 (1.5–1.8) (mmol L−1) and 3.0 (2.4–3.9) to 1.3 (1.1–1.8) (mmol L−1) in the E10/S10 and S80 groups respectively. In the entire study group (n = 32), LDF parameters increased significantly; postocclusive LDF from 22 (17–27) to 26 (21–32) perfusion units (PU) (P < 0.001), heat foot LDF from 61 (44–82) to 66 (45–83) PU (P < 0.001) and heat arm LDF from 60 (48–121) to 75 (54–125) PU (P < 0.01). The changes in LDF parameters did not differ between the E10/S10 and S80 groups.Conclusions.  Lipid lowering improves microvascular function in patients with dysglycaemia and CAD. The data suggest that lipid lowering per se is more important than pleiotropic effects of statins for this effect.
Variable patterns of introgression in two sculpin hybrid zones suggest that genomic isolation differs among populations
Authors: NOLTE A. W. , GOMPERT Z. , BUERKLE C. A. 
Published: May 2009

AbstractTheory predicts that reproductive isolation may be due to intrinsic genetic incompatibilities or extrinsic ecological factors. Therefore, an understanding of the genetic basis of isolation may require analyses of evolutionary processesin situto include environmental factors. Here we study genetic isolation between populations of sculpins (Cottus) at 168 microsatellites. Genomic clines were fit using 480 individuals sampled across independent natural hybrid zones that have formed between one invading species and two separate populations of a resident species. Our analysis tests for deviations from neutral patterns of introgression at individual loci based on expectations given genome‐wide admixture. Roughly 51% of the loci analysed displayed significant deviations. An overall deficit of interspecific heterozygotes in 26% and 21% of the loci suggests that widespread underdominance drives genomic isolation. At the same time, selection promotes introgression of almost 30% of the markers, which implies that hybridization may increase the fitness of admixed individuals. Cases of overdominance or epistatic interactions were relatively rare. Despite the similarity of the two hybrid zones in their overall genomic composition, patterns observed at individual loci show little correlation between zones and many fit different genotypic models of fitness. At this point, it remains difficult to determine whether these results are due to differences in external selection pressures or cryptic genetic differentiation of distinct parental populations. In the future, data from mapped genetic markers and on variation of ecological factors will provide additional insights into the contribution of these factors to variation in the evolutionary consequences of hybridization.
Incipient ring speciation revealed by a migratory divide
Authors: IRWIN DARREN E. 
Published: May 2009

Ever since Ernst Mayr (1942) called ring species the ‘perfect demonstration of speciation’, they have attracted much interest from researchers examining how two species evolve from one. In a ring species, two sympatric and reproductively isolated forms are connected by a long chain of intermediate populations that encircle a geographic barrier. Ring species have the potential to demonstrate that speciation can occur without complete geographic isolation, in contrast to the classic model of allopatric speciation. They also allow researchers to examine the causes of reproductive isolation in the contact zone and to use spatial variation to infer the steps by which speciation occurs. According to the classical definition, a ring species must have (i) gradual variation through a chain of populations connecting two divergent and sympatric forms, and (ii) complete or nearly complete reproductive isolation between the terminal forms. But evolutionary biologists now recognize that the process of speciation might often occur with some periods of geographic contact and hybridization between diverging forms; during these phases, even partial reproductive isolation can limit gene flow and permit further divergence to occur. In this issue Bensch et al. (2009) make an exciting and important contribution by extending the ring species concept to a case in which the divergence is much younger and not yet advanced to full reproductive isolation. Their study of geographic variation in willow warblers (Phylloscopus trochilus; Fig. 1) provides a beautiful example of gradual variation through a ring of populations connecting two forms that are partially reproductively isolated where they meet, possibly due to divergent migratory behaviours of the terminal forms. A male willow warbler resembling the southeastern‐migrating form (Phylloscopus trochilus acredula), on its breeding territory in central Sweden. (Photo: Anders Hedenström).image
Time‐shifted reproductive behaviours among fall armyworm (Noctuidae: Spodoptera frugiperda) host strains: evidence for differing modes of inheritance
Authors: SCHÖFL G. , HECKEL D. G. , GROOT A. T. 
Published: May 2009

AbstractThe noctuid moth Spodoptera frugiperda consists of two strains associated with different larval host plants (most notably corn and rice). These strains exhibit differential temporal patterns of female calling and copulation during scotophase, with the corn strain more active earlier in the night. We investigated strain‐specific constraints in reproductive timing, mating interactions between the two strains, and the mode of inheritance of timing of female calling, male calling, copulation and oviposition. We observed an allochronic shift of all reproductive behaviours by approximately 3 h and a parallel shift of nonreproductive locomotor activity, suggesting involvement of the circadian clock. The corn strain was more variable in the timing of calling and copulation than the rice strain. Rice strain females were more restricted in the timing of copulation than rice strain males, while such differences between the sexes were not apparent in the corn strain. There were significant interactions between the strains affecting onset times of copulation and male calling. The four investigated reproductive traits differed in their modes of inheritance: timing of female and male calling exhibited strong maternal effects, timing of copulation was controlled by a combination of maternal effects and corn strain dominant autosomal factors, and timing of oviposition was inherited in a corn strain dominant fashion. We conclude that the allochronic separation of reproduction between fall armyworm strains is asymmetric, less pronounced than previously thought, and under complex genetic control.
Experimental modifications imply a stimulatory function for male tsetse fly genitalia, supporting cryptic female choice theory
Authors: BRICEÑO R. D. , EBERHARD W. G. 
Published: May 2009

AbstractOne of the most sweeping of all patterns in morphological evolution is that animal genitalia tend to diverge more rapidly than do other structures. Abundant indirect evidence supports the cryptic female choice (CFC) explanation of this pattern, which supposes that male genitalia often function to court females during copulation; but direct experimental demonstrations of a stimulatory function have been lacking. In this study, we altered the form of two male genital structures that squeeze the female’s abdomen rhythmically in Glossina pallidipes flies. As predicted by theory, this induced CFC against the male: ovulation and sperm storage decreased, while female remating increased. Further experiments showed that these effects were due to changes in tactile stimuli received by the female from the male’s altered genitalia, and were not due to other possible changes in the males due to alteration of their genital form. Stimulation from male genital structures also induces females to permit copulation to occur. Together with previous studies of tsetse reproductive physiology, these data constitute the most complete experimental confirmation that sexual selection (probably by CFC) acts on the stimulatory properties of male genitalia.