bluuebunny/crossref_metadata_2025 huggingface dataset:
An expanded view of Lada Terra, Venus: New Arecibo radar observations of Quetzalpetlatl Corona and surrounding flows
Authors: Kratter Kaitlin M. , Carter Lynn M. , Campbell Donald B.
Published: April 2007

Quetzalpetlatl, a corona approximately 800 km in diameter, lies in Lada Terra centered at 68°S, 357°E. It is characterized by vast, radar‐bright lava flows stretching to the southeast for over 1500 km, covering a total area of nearly 600,000 km2. Magellan SAR images covered most of the Quetzalpetlatl flow field, but 12.6 cm Arecibo radar data from March 2001 gives complete coverage of the region. With these new data, we examine the circular polarization properties of the Quetzalpetlatl flow field for comparison with other flows on Venus as well as terrestrial lava. Our analysis suggests that Quetzalpetlatl Corona is primarily a source for flows with 13‐cm‐scale roughness properties similar to terrestrial pahoehoe, and which appear to have traveled down a system of channels or tubes until reaching some unresolved topographic boundary. We also identify four new crater candidates.
Using invariant altitude (hinv) for mapping of the radiation belt fluxes in the low‐altitude environment
Authors: Cabrera Juan , Lemaire Joseph
Published: April 2007

Mapping of the radiation belt environment in the classical (B, L) invariant coordinates is rather poorly resolved at low altitudes where the SAMPEX and DEMETER missions are collecting scientific data. This lack of adequate spatial resolution at low altitudes has been pointed out since 1986. A simple solution to this standing problem is proposed in this article. We recall alternative coordinates that were proposed in the 90s to improve the spatial resolution of binning meshes and radiation belt maps in the low‐altitude region, i.e., near the atmospheric cutoff. Next, we define a new coordinate: the “invariant altitude,” hinv, that we recommend instead of B or other invariant drift shell coordinates like B/B0 or α0, the equatorial pitch angle. In McIlwain's reference dipole, the new coordinate, hinv, corresponds to the altitude (in units of km) of mirror points of particles which have given values of B and I or L, calculated by using a geomagnetic field model like the International Geomagnetic Reference Field. The advantages and limitations of the new hinv coordinate are presented. For illustration, the distributions of the omnidirectional fluxes of electrons and protons predicted by the standard AE8 and AP8 radiation belt models are displayed using this new invariant coordinate, as well as by using alternative invariant coordinates like B/B0 or α0. A set of orbits of the SAMPEX, DEMETER, and CRRES spacecraft are displayed in these different coordinate systems to illustrate the advantage of using the invariant altitude hinv to map the radiation belt environment at low altitudes.
Zircon Hf isotopic constraints on the sources of the Indus Molasse, Ladakh Himalaya, India
Authors: Wu Fu‐Yuan , Clift Peter D. , Yang Jin‐Hui
Published: April 2007

India‐Asia collision has resulted in the largest orogenic event on Earth since at least 500 Ma, and this has had a profound influence on the drainage patterns of Asia, on the Asian monsoon climate, on global oceanography, as well as on faunal extinctions. Despite this importance, understanding of the Paleogene evolution of this system is limited. U‐Pb and Lu‐Hf isotopic analyses of detrital zircons from the clastic sedimentary rocks of the Indus Molasse, located within the Indus Suture of the Ladakh Himalaya, India, show that most have Mesozoic‐Cenozoic ages and juvenile Hf isotopic compositions. This suggests that the main source of these sediments is the Transhimalayan batholith, with minor flux from the Lhasa‐Karakoram terrane and Indian plate. The lower Indus Molasse (Chogdo Formation) is inferred to have been deposited at 60–49 Ma, whereas the upper Choksti Formation was deposited later than 45–41 Ma and contains a greater contribution from the Lhasa terrane. The Transhimalayan batholith was eroded throughout Indus Molasse sedimentation, but increasing exhumation of Lhasa‐Karakoram terrane indicates its progressive uplift after initial collision, and requires formation of a paleo‐Indus River shortly after collision.
Empirical ground‐motion prediction equations for northwestern Turkey using the aftershocks of the 1999 Kocaeli earthquake
Authors: Bindi D. , Parolai S. , Grosser H. , Milkereit C. , Durukal E.
Published: April 2007

We present ground motion models for northwestern Turkey using the aftershocks of the Mw 7.4, 1999 Kocaeli earthquake. We consider 4047 velocity and acceleration records for each component of motion, from 528 earthquakes recorded by stations belonging to regional networks. The ground motion models obtained provide peak ground velocity, peak ground acceleration, and spectral accelerations for 8 different frequencies between 1 and 10 Hz. The analysis of the error distribution shows that the record‐to‐record component of variance is the largest contribution to the standard deviation of the calibrated ground‐ motion models. Furthermore, a clear dependence of inter‐event error on stress drop is observed. The empirical ground‐motion prediction equations, derived for both the larger horizontal and vertical components, are valid in the local magnitude range from 0.5 to 5.9, and for hypocentral distances up to 190 km.
A Neuroprotective Function for the Hematopoietic Protein Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF)
Authors: Schäbitz Wolf-Rüdiger , Krüger Carola , Pitzer Claudia , Weber Daniela , Laage Rico , Gassler Nikolaus , Aronowski Jaroslaw , Mier Walter , Kirsch Friederike , Dittgen Tanjew , Bach Alfred , Sommer Clemens , Schneider Armin
Published: April 2007

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic cytokine responsible for the proliferation, differentiation, and maturation of cells of the myeloid lineage, which was cloned more than 20 years ago. Here we uncovered a novel function of GM-CSF in the central nervous system (CNS). We identified the GM-CSF α-receptor as an upregulated gene in a screen for ischemia-induced genes in the cortex. This receptor is broadly expressed on neurons throughout the brain together with its ligand and induced by ischemic insults. In primary cortical neurons and human neuroblastoma cells, GM-CSF counteracts programmed cell death and induces BCL-2 and BCL-Xl expression in a dose- and time-dependent manner. Of the signaling pathways studied, GM-CSF most prominently induced the PI3K-Akt pathway, and inhibition of Akt strongly decreased antiapoptotic activity. Intravenously given GM-CSF passes the blood—brain barrier, and decreases infarct damage in two different experimental stroke models (middle cerebral artery occlusion (MCAO), and combined common carotid/distal MCA occlusion) concomitant with induction of BCL-Xl expression. Thus, GM-CSF acts as a neuroprotective protein in the CNS. This finding is remarkably reminiscent of the recently discovered functionality of two other hematopoietic factors, erythropoietin and granulocyte colony-stimulating factor in the CNS. The identification of a third hematopoietic factor acting as a neurotrophic factor in the CNS suggests a common principle in the functional evolution of these factors. Clinically, GM-CSF now broadens the repertoire of hematopoietic factors available as novel drug candidates for stroke and neurodegenerative diseases.
Vaccination of cattle against the Boophilus microplus using a mucin‐like membrane glycoprotein
Authors: McKENNA ROBERT V. , RIDING GEORGE A. , JARMEY JANINE M. , PEARSON ROGER D. , WILLADSEN PETER
Published: April 2007

An antigen, BMA7, which induced partial immunity against tick infestation has been isolated from Boophilus microplus using two different protein fractionation protocols, accompanied by vaccination and parasite challenge trials. The antigen is a 63 kDa glycoprotein isolated from semi‐engorged adult female ticks. Though significant, the induced immunity is less striking than that previously reported for antigen Bm86 from the same parasite. However, co‐vaccination with Bm86 and BMA7 can enhance immunity over that seen with a commercial vaccine based on Bm86 alone. Limited peptide sequence information shows significant variation in the BMA7 protein occurs. The antigen has approximately 36 kDa of glycosylation, in both N‐linked and O‐linked oligosaccharides. There is evidence that both polypeptide and oligosaccharide are antigenic, but the chemical nature of the protective antigenic sites is not clear. There is little or no immunological response to the antigen during natural infestation with parasites, suggesting the antigen is ‘concealed’ and protective immunity dependent on artificial vaccination. The antigen has some similarities with the vertebrate mucins. It is widely distributed in tick tissues and membrane bound but its function is currently unknown.
Seoul: Birth of a Broadband Metropolis
Authors: Townsend Anthony M
Published: April 2007

Following half a century of breakneck urbanization, the capital of South Korea emerged in the late 1990s as the most digitally networked city in the world. With nearly 80% household broadband penetration in 2004, Seoul surpassed global cities and ‘technopoles' in speed and comprehensiveness in embracing broadband technology. In this paper I describe the physical development of Seoul's broadband infrastructure and its frequent intersections with daily urban life. As the fourth largest urban agglomeration in the world, Seoul offers a unique case for investigating the intersection of telecommunications policy, development, and culture in large metropolitan regions, as well as the everyday implications of pervasive computing. It also highlights emerging challenges and opportunities presented by the rapid and widespread deployment of digital network infrastructure.
Transformation of Spatial Data to a New Zone System: A Survey of US Metropolitan Planning Organizations
Authors: Hess Daniel Baldwin
Published: April 2007

This study reports on a survey of Metropolitan Planning Organizations (MPOs) in the USA to collect information about spatial data transformation, a geographic procedure used to convert data from one set of zones (system A) to a different set of zones (system B), where systems A and B have incompatible zone boundaries. The survey reveals that 60% of MPOs perform spatial data transformation more than once per year, usually using the simplest, most error-prone methods. Given a lag in application of new GIS techniques among planners, it is perhaps not surprising that practising planners tend to favor simpler methods of spatial data transformation, despite the widely documented shortcomings of such techniques in the literature. These findings suggest that the gap between research and application in the utilization of GIS in planning practice will require both more advanced training of planners using GIS, and, perhaps more importantly, greater sophistication among the ‘consumers' of GIS planning analyses—non-GIS planners, public officials, and the general public.
Understanding and Representing the Social Prospects of Hybrid Urban Spaces
Authors: Paay Jeni , Dave Bharat , Howard Steve
Published: April 2007

As built environments become increasingly hybrid physical, social, and digital spaces, the intersecting issues of spatial context, sociality, and pervasive digital technologies need to be understood when designing for interactions in these hybrid spaces. Architectural and interaction designers need a mechanism that provides them with an understanding of the ‘sociality-places-bits' nexus. Using a specific urban setting as an analytical case study, we present a methodology to capture this nexus in a form that designers of hybrid spaces can effectively apply as a tool to augment digitally sociality in a built environment.
The impact of herbivore–plant coevolution on plant community structure
Authors: Becerra Judith X.
Published: April 2007

Coevolutionary theory proposes that the diversity of chemical structures found in plants is, in large part, the result of selection by herbivores. Because herbivores often feed on chemically similar plants, they should impose selective pressures on plants to diverge chemically or bias community assembly toward chemical divergence. Using a coevolved interaction between a group of chrysomelid beetles and their host plants, I tested whether coexisting plants of the Mexican tropical dry forest tend to be chemically more dissimilar than random. Results show that some of the communities are chemically overdispersed and that overdispersion is related to the tightness of the interaction between plants and herbivores and the spatial scale at which communities are measured. As coevolutionary specialization increases and spatial scale decreases, communities tend to be more chemically dissimilar. At fairly local scales and where herbivores have tight, one-to-one interactions with plants, communities have a strong pattern of chemical disparity.
Structure and tie strengths in mobile communication networks
Authors: Onnela J.-P. , Saramäki J. , Hyvönen J. , Szabó G. , Lazer D. , Kaski K. , Kertész J. , Barabási A.-L.
Published: April 2007

Electronic databases, from phone to e-mails logs, currently provide detailed records of human communication patterns, offering novel avenues to map and explore the structure of social and communication networks. Here we examine the communication patterns of millions of mobile phone users, allowing us to simultaneously study the local and the global structure of a society-wide communication network. We observe a coupling between interaction strengths and the network's local structure, with the counterintuitive consequence that social networks are robust to the removal of the strong ties but fall apart after a phase transition if the weak ties are removed. We show that this coupling significantly slows the diffusion process, resulting in dynamic trapping of information in communities and find that, when it comes to information diffusion, weak and strong ties are both simultaneously ineffective.
Frequency and phenotypic implications of mitochondrial DNA mutations in human squamous cell cancers of the head and neck
Authors: Zhou Shaoyu , Kachhap Sushant , Sun Wenyue , Wu Guojun , Chuang Alice , Poeta Luana , Grumbine Lawson , Mithani Suhail K. , Chatterjee Aditi , Koch Wayne , Westra William H. , Maitra Anirban , Glazer Chad , Carducci Michael , Sidransky David , McFate Thomas , Verma Ajay , Califano Joseph A.
Published: April 2007

Mitochondrial genomic mutations are found in a variety of human cancers; however, the frequency of mitochondrial DNA (mtDNA) mutations in coding regions remains poorly defined, and the functional effects of mitochondrial mutations found in primary human cancers are not well described. Using MitoChip, we sequenced the whole mitochondrial genome in 83 head and neck squamous cell carcinomas. Forty-one of 83 (49%) tumors contained mtDNA mutations. Mutations occurred within noncoding (D-loop) and coding regions. A nonrandom distribution of mutations was found throughout the mitochondrial enzyme complex components. Sequencing of margins with dysplasia demonstrated an identical nonconservative mitochondrial mutation (A76T in ND4L) as the tumor, suggesting a role of mtDNA mutation in tumor progression. Analysis of p53 status showed that mtDNA mutations correlated positively with p53 mutations (
P
< 0.002). To characterize biological function of the mtDNA mutations, we cloned NADH dehydrogenase subunit 2 (ND2) mutants based on primary tumor mutations. Expression of the nuclear-transcribed, mitochondrial-targeted ND2 mutants resulted in increased anchorage-dependent and -independent growth, which was accompanied by increased reactive oxygen species production and an aerobic glycolytic metabolic phenotype with hypoxia-inducible factor (HIF)-1α induction that is reversible by ascorbate. Cancer-specific mitochondrial mutations may contribute to development of a malignant phenotype by direct genotoxic effects from increased reactive oxygen species production as well as induction of aerobic glycolysis and growth promotion.
Stoichiometric controls of mercury dilution by growth
Authors: Karimi Roxanne , Chen Celia Y. , Pickhardt Paul C. , Fisher Nicholas S. , Folt Carol L.
Published: April 2007

Rapid growth could significantly reduce methylmercury (MeHg) concentrations in aquatic organisms by causing a greater than proportional gain in biomass relative to MeHg (somatic growth dilution). We hypothesized that rapid growth from the consumption of high-quality algae, defined by algal nutrient stoichiometry, reduces MeHg concentrations in zooplankton, a major source of MeHg for lake fish. Using a MeHg radiotracer, we measured changes in MeHg concentrations, growth and ingestion rates in juvenile
Daphnia pulex
fed either high (C:P = 139) or low-quality (C:P = 1317) algae (
Ankistrodesmus falcatus
) for 5 d. We estimated
Daphnia
steady-state MeHg concentrations, using a biokinetic model parameterized with experimental rates.
Daphnia
MeHg assimilation efficiencies (≈95%) and release rates (0.04 d
−1
) were unaffected by algal nutrient quality. However,
Daphnia
growth rate was 3.5 times greater when fed high-quality algae, resulting in pronounced somatic growth dilution. Steady-state MeHg concentrations in
Daphnia
that consumed high-quality algae were one-third those of
Daphnia
that consumed low-quality algae due to higher growth and slightly lower ingestion rates. Our findings show that rapid growth from high-quality food consumption can significantly reduce the accumulation and trophic transfer of MeHg in freshwater food webs.
Following evolution's lead to a single residue switch for diterpene synthase product outcome
Authors: Xu Meimei , Wilderman P. Ross , Peters Reuben J.
Published: April 2007

There have been few insights into the biochemical origins of natural product biosynthesis from primary metabolism. Of particular interest are terpene synthases, which often mediate the committed step in particular biosynthetic pathways so that alteration of their product outcome is a key step in the derivation of novel natural products. These enzymes also catalyze complex reactions of significant mechanistic interest. Following an evolutionary lead from two recently diverged, functionally distinct diterpene synthase orthologs from different subspecies of rice, we have identified a single residue that can switch product outcome. Specifically, the mutation of a conserved isoleucine to threonine that acts to convert not only the originally targeted isokaurene synthase into a specific pimaradiene synthase but also has a much broader effect, which includes conversion of the
ent
-kaurene synthases found in all higher plants for gibberellin phytohormone biosynthesis to the production of pimaradiene. This surprisingly facile switch for diterpene synthase catalytic specificity indicates the ease with which primary (gibberellin) metabolism can be subverted to secondary biosynthesis and may underlie the widespread occurrence of pimaradiene-derived natural products. In addition, because this isoleucine is required for the mechanistically more complex cyclization to tetracyclic kaurene, whereas substitution with threonine “short-circuits” this mechanism to produce the “simpler” tricyclic pimaradiene, our results have some implications regarding the means by which terpene synthases specify product outcome.
Distinct functional motifs within the IL-17 receptor regulate signal transduction and target gene expression
Authors: Maitra Amarnath , Shen Fang , Hanel Walter , Mossman Karen , Tocker Joel , Swart David , Gaffen Sarah L.
Published: April 2007

IL-17 is the founding member of a novel family of proinflammatory cytokines that defines a new class of CD4+effector T cells, termed “Th17.” Mounting evidence suggests that IL-17 and Th17 cells cause pathology in autoimmunity, but little is known about mechanisms of IL-17RA signaling. IL-17 through its receptor (IL-17RA) activates genes typical of innate immune cytokines, such as TNFα and IL-1β, despite minimal sequence similarity in their respective receptors. A previous bioinformatics study predicted a subdomain in IL-17-family receptors with homology to a Toll/IL-1R (TIR) domain, termed the “SEFIR domain.” However, the SEFIR domain lacks motifs critical for bona fide TIR domains, and its functionality was never verified. Here, we used a reconstitution system in IL-17RA-null fibroblasts to map functional domains within IL-17RA. We demonstrate that the SEFIR domain mediates IL-17RA signaling independently of classic TIR adaptors, such as MyD88 and TRIF. Moreover, we identified a previously undescribed“TIR-like loop” (TILL) required for activation of NF-κB, MAPK, and up-regulation of C/EBPβ and C/EBPδ. Mutagenesis of the TILL domain revealed a site analogous to the LPSdmutation in TLR4, which renders mice insensitive to LPS. However, a putative salt bridge typically found in TIR domains appears to be dispensable. We further identified a C-terminal domain required for activation of C/EBPβ and induction of a subset IL-17 target genes. This structure-function analysis of a IL-17 superfamily receptor reveals important differences in IL-17RA compared with IL-1/TLR receptors.
The structure of a birnavirus polymerase reveals a distinct active site topology
Authors: Pan Junhua , Vakharia Vikram N. , Tao Yizhi Jane
Published: April 2007

Single-subunit polymerases are universally encoded in both cellular organisms and viruses. Their three-dimensional structures have the shape of a right-hand with the active site located in the palm region, which has a topology similar to that of the RNA recognition motif (RRM) found in many RNA-binding proteins. Considering that polymerases have well conserved structures, it was surprising that the RNA-dependent RNA polymerases from birnaviruses, a group of dsRNA viruses, have their catalytic motifs arranged in a permuted order in sequence. Here we report the 2.5 Å structure of a birnavirus VP1 in which the polymerase
palm
subdomain adopts a new active site topology that has not been previously observed in other polymerases. In addition, the polymerase motif C of VP1 has the sequence of -ADN-, a highly unusual feature for RNA-dependent polymerases. Through site-directed mutagenesis, we have shown that changing the VP1 motif C from -ADN- to -GDD- results in a mutant with an increased RNA synthesis activity. Our results indicate that the active site topology of VP1 may represent a newly developed branch in polymerase evolution, and that birnaviruses may have acquired the -ADN- mutation to control their growth rate.
Discovery of platencin, a dual FabF and FabH inhibitor with
in vivo
antibiotic properties
Authors: Wang Jun , Kodali Srinivas , Lee Sang Ho , Galgoci Andrew , Painter Ronald , Dorso Karen , Racine Fred , Motyl Mary , Hernandez Lorraine , Tinney Elizabeth , Colletti Steven L. , Herath Kithsiri , Cummings Richard , Salazar Oscar , González Ignacio , Basilio Angela , Vicente Francisca , Genilloud Olga , Pelaez Fernando , Jayasuriya Hiranthi , Young Katherine , Cully Doris F. , Singh Sheo B.
Published: April 2007

Emergence of bacterial resistance is a major issue for all classes of antibiotics; therefore, the identification of new classes is critically needed. Recently we reported the discovery of platensimycin by screening natural product extracts using a target-based whole-cell strategy with antisense silencing technology in concert with cell free biochemical validations. Continued screening efforts led to the discovery of platencin, a novel natural product that is chemically and biologically related but different from platensimycin. Platencin exhibits a broad-spectrum Gram-positive antibacterial activity through inhibition of fatty acid biosynthesis. It does not exhibit cross-resistance to key antibiotic resistant strains tested, including methicillin-resistant
Staphylococcus aureus
, vancomycin-intermediate
S. aureus
, and vancomycin-resistant
Enterococci
. Platencin shows potent
in vivo
efficacy without any observed toxicity. It targets two essential proteins, β-ketoacyl-[acyl carrier protein (ACP)] synthase II (FabF) and III (FabH) with IC
50
values of 1.95 and 3.91 μg/ml, respectively, whereas platensimycin targets only FabF (IC
50
= 0.13 μg/ml) in
S. aureus
, emphasizing the fact that more antibiotics with novel structures and new modes of action can be discovered by using this antisense differential sensitivity whole-cell screening paradigm.
The macrophage-stimulating protein pathway promotes metastasis in a mouse model for breast cancer and predicts poor prognosis in humans
Authors: Welm Alana L. , Sneddon Julie B. , Taylor Carmen , Nuyten Dimitry S. A. , van de Vijver Marc J. , Hasegawa Bruce H. , Bishop J. Michael
Published: April 2007

A better understanding of tumor metastasis requires development of animal models that authentically reproduce the metastatic process. By modifying an existing mouse model of breast cancer, we discovered that macrophage-stimulating protein promoted breast tumor growth and metastasis to several organs. A special feature of our findings was the occurrence of osteolytic bone metastases, which are prominent in human breast cancer. To explore the clinical relevance of our model, we examined expression levels of three genes involved in activation of the MSP signaling pathway (MSP,MT-SP1, andMST1R) in human breast tumors. We found that overexpression ofMSP,MT-SP1, andMST1Rwas a strong independent indicator of both metastasis and death in human breast cancer patients and significantly increased the accuracy of an existing gene expression signature for poor prognosis. These data suggest that signaling initiated by MSP is an important contributor to metastasis of breast cancer and introduce an independent biomarker for assessing the prognosis of humans with breast cancer.
Costly steroids: egg testosterone modulates nestling metabolic rate in the zebra finch
Authors: Tobler Michael , Nilsson Jan-Åke , Nilsson Johan F
Published: April 2007

The transfer of non-genetic resources from mother to the offspring often has considerable consequences for offspring performance. In birds, maternally derived hormones are known to influence a variety of morphological, physiological and behavioural traits in the chick. So far, the range of these hormonal effects involves benefits in terms of enhanced growth and competitive ability as well as costs in terms of immunosuppression. However, since yolk hormones can enhance growth and begging activity, high levels of these hormones may also involve energetic costs. Here, we show experimentally that elevated levels of prenatal testosterone increase resting metabolic rate in nestling zebra finches (
Taeniopygia guttata
). Surprisingly, however, elevation of prenatal testosterone did not result in higher growth rates and, thus, differences in resting metabolism do not seem to be linked to nestling growth. We conclude that apart from immunosuppressive effects, high levels of egg steroids may also entail costs in terms of increased energy expenditure.
Daytime noise predicts nocturnal singing in urban robins
Authors: Fuller Richard A , Warren Philip H , Gaston Kevin J
Published: April 2007

Ambient noise interferes with the propagation of acoustic signals through the environment from sender to receiver. Over the past few centuries, urbanization and the development of busy transport networks have led to dramatic increases in the levels of ambient noise with which animal acoustic communications must compete. Here we show that urban European robins
Erithacus rubecula
, highly territorial birds reliant on vocal communication, reduce acoustic interference by singing during the night in areas that are noisy during the day. The effect of ambient light pollution, to which nocturnal singing in urban birds is frequently attributed, is much weaker than that of daytime noise.
An increase in pH boosts olfactory communication in sticklebacks
Authors: Heuschele Jan , Candolin Ulrika
Published: April 2007

Human-induced eutrophication is a serious environmental problem that constrains visual communication and influences the mate choice process in fishes. Eutrophication also changes the chemical environment and the pH of the water, which could influence the use of olfactory cues in mate choice. Here, we show that an increase in pH enhances the use of male olfactory cues in mate choice in three-spined sticklebacks,Gasterosteus aculeatus. In a laboratory choice experiment, gravid females were more attracted to male olfactory cues when pH was raised. This could compensate for impaired visual communication in eutrophied waters and facilitate adaptive mate choice.
The canine distemper epidemic in Serengeti: are lions victims of a new highly virulent canine distemper virus strain, or is pathogen circulation stochasticity to blame?
Authors: Guiserix Micheline , Bahi-Jaber Narges , Fouchet David , Sauvage Frank , Pontier Dominique
Published: April 2007

In the year 1994, the Serengeti lion population was decimated by a canine distemper disease outbreak. Retrospective investigations showed that this host population had already been in contact with the pathogen in 1981 without any detected sign of disease. As an alternative to the virus mutation hypothesis to explain this difference in virulences observed in 1981 and 1994, we propose a novel mechanism of disease emergence based on variation in population immunity. We use a stochastic model to show that stochastic fluctuations in pathogen circulation, owing to a low probability of virus transmission from its reservoir to the target host and thereby resulting in variations in the global immunity level of the target host population, can explain the observations made in Serengeti. This mechanism may also be involved in other infectious disease emergences or re-emergences.
Fidelity and over-wintering of sea turtles
Authors: Broderick Annette C , Coyne Michael S , Fuller Wayne J , Glen Fiona , Godley Brendan J
Published: April 2007

While fidelity to breeding sites is well demonstrated in marine turtles, emerging knowledge of migratory routes and key foraging sites is of limited conservation value unless levels of fidelity can be established. We tracked green (
Chelonia mydas
,
n
=10) and loggerhead (
Caretta caretta
,
n
=10) turtles during their post-nesting migration from the island of Cyprus to their foraging grounds. After intervals of 2–5 years, five of these females were recaptured at the nesting beach and tracked for a second migration. All five used highly similar migratory routes to return to the same foraging and over-wintering areas. None of the females visited other foraging habitats over the study period (units lasted on average 305 days; maximum, 1356 days), moving only to deeper waters during the winter months where they demonstrated extremely long resting dives of up to 10.2 h (the longest breath-holding dive recorded for a marine vertebrate). High levels of fidelity and the relatively discrete nature of the home ranges demonstrate that protection of key migratory pathways, foraging and over-wintering sites can serve as an important tool for the future conservation of marine turtles.
Evidence of ancient DNA reveals the first European lineage in Iron Age Central China
Authors: Xie C.Z , Li C.X , Cui Y.Q , Zhang Q.C , Fu Y.Q , Zhu H , Zhou H
Published: April 2007

Various studies on ancient DNA have attempted to reconstruct population movement in Asia, with much interest focused on determining the arrival of European lineages in ancient East Asia. Here, we discuss our analysis of the mitochondrial DNA of human remains excavated from the Yu Hong tomb in Taiyuan, China, dated 1400 years ago. The burial style of this tomb is characteristic of Central Asia at that time. Our analysis shows that Yu Hong belonged to the haplogroup U5, one of the oldest western Eurasian-specific haplogroups, while his wife can be classified as haplogroup G, the type prevalent in East Asia. Our findings show that this man with European lineage arrived in Taiyuan approximately 1400 years ago, and most probably married a local woman. Haplogroup U5 was the first west Eurasian-specific lineage to be found in the central part of ancient China, and Taiyuan may be the easternmost location of the discovered remains of European lineage in ancient China.
Status‐signalling chemical badges in male Iberian rock lizards
Authors: MARTÍN J. , MOREIRA P. L. , LÓPEZ P.
Published: April 2007

Male competition for females often results in the evolution of conspicuous male traits that signal fighting ability or dominance status. Most studies examining mechanisms allowing these traits to function as reliable status signals (or badges) have focused on conspicuous visual or acoustic traits. However, many animals communicate chemically, and chemical traits alone may also signal male dominance status.

We examined whether chemicals in femoral gland secretions of male Iberian rock lizards (Lacerta monticola monticola Boulenger 1905) may signal dominance status.

In staged encounters, larger males were dominant over smaller ones. While controlling for male body size, males of higher dominance status produced femoral secretions with higher proportions of hexadecanol and octadecanol.

Tongue‐flick assays showed that males were able to (1) discriminate, by chemosensory cues alone, the different concentrations of hexadecanol from other chemicals presented in femoral secretions; (2) respond aggressively towards hexadecanol while responding neutrally towards other chemicals; and (3) show differential chemosensory and aggressive behaviours towards hexadecanol according to their own dominance status.

These results suggest that hexadecanol may be a reliable status badge. Moreover, because hexadecanol elicits male aggressive behaviour, subordinate males signalling high status (‘cheaters’) may end up paying high fighting costs. In addition, males that had higher dominance status, and that allocated higher proportions of hexadecanol to femoral secretions, had greater T‐cell immune responses. This result suggests a possible link between quality of the immune system, dominance status, and chemical signals.
Maternal carotenoid supplementation does not affect breeding performance in the Great Tit (Parus major)
Authors: REMEŠ VLADIMÍR , KRIST MILOŠ , BERTACCHE VITTORIO , STRADI RICCARDO
Published: April 2007

Carotenoids are micronutrients with many beneficial health‐related effects. They are effective antioxidants and stimulants of the immune system. Carotenoids cannot be synthesized in animals and must be obtained from food. As such, they may limit reproductive output and performance, and on the proximate level mediate reproductive trade‐offs.

We studied carotenoid limitation in wild Great Tits (Parus major) by supplementing prelaying and laying females with lutein, the most abundant carotenoid in this species. We followed the effects of this supplementation on egg yolk carotenoid composition, and offspring and parental performance.

Females transferred the supplemented lutein into egg yolks, increasing lutein concentration to the upper limit of naturally occurring concentrations in control pairs. Concentrations of zeaxanthin, β‐carotene and α‐carotene did not differ between supplemented and control pairs.

Effects on offspring and parental performance were generally absent or weak. There were no effects on timing of laying, clutch size, hatching success, nestling survival, nestling mass (day 6 and 14), tarsus length or T‐cell mediated immune response. Males on supplemented nests fed their young more than those on control nests. There was no positive effect on female feeding or mass.

Negligible effects of lutein supplementation on offspring and parental performance might be explained by high natural abundance of carotenoids or other antioxidants, where additional carotenoids bear no strong advantage to the birds. Additionally, conflicting results of different studies may be explained by species‐specific features of their life‐histories.
A functional approach to sexual selection
Authors: IRSCHICK DUNCAN J. , HERREL ANTHONY , VANHOOYDONCK BIEKE , DAMME RAOUL VAN
Published: April 2007

Sexual selection theory is a robust and dynamic field within evolutionary biology, yet despite decades of research, remarkably little is known of the mechanistic bases of mate choice and male competition.

Because many aspects of sexual selection involve dynamic movements, and are physically challenging, the limits of sexual selection may be defined by key functional and physiological variables (i.e. the ‘functional approach’).

We advocate the functional approach for providing mechanistic resolution on the adaptive basis of sexual structures and signals, the nature of mate choice and how males compete, among other issues.

An overview of recent work, highlighted in this special issue, shows that many features of sexual selection, including the outcome of male fights, the morphology and design of sexual signals, and the nature of mate choice, all appear to be dictated in large part by functional and physiological parameters.

We argue that the functional approach provides a potent tool for resolving several unresolved issues in sexual selection theory, particularly the nature of male quality, the handicap and indicator models of sexual selection, and the basis of mate choice.
Historical changes in the phenology of British Odonata are related to climate
Authors: HASSALL CHRISTOPHER , THOMPSON DAVID J. , FRENCH GRAHAM C. , HARVEY IAN F.
Published: April 2007

Responses of biota to climate change take a number of forms including distributional shifts, behavioural changes and life history changes. This study examined an extensive set of biological records to investigate changes in the timing of life history transitions (specifically emergence) in British Odonata between 1960 and 2004. The results show that there has been a significant, consistent advance in phenology in the taxon as a whole over the period of warming that is mediated by life history traits. British odonates significantly advanced the leading edge (first quartile date) of the flight period by a mean of 1.51 ±0.060 (SEM, n=17) days per decade or 3.08±1.16 (SEM, n=17) days per degree rise in temperature when phylogeny is controlled for. This study represents the first review of changes in odonate phenology in relation to climate change. The results suggest that the damped temperature oscillations experienced by aquatic organisms compared with terrestrial organisms are sufficient to evoke phenological responses similar to those of purely terrestrial taxa.
Effects of elevated atmospheric CO2, cutting frequency, and differential day/night atmospheric warming on root growth and turnover of Phalaris swards
Authors: VOLDER ASTRID , GIFFORD ROGER M. , EVANS JOHN R.
Published: April 2007

We investigated seasonal root production and root turnover of fertilized and well‐watered monocultures of Phalaris for 2 years using minirhizotrons installed in six newly designed temperature gradient tunnels, combined with sequential soil coring. Elevated atmospheric CO2 treatments were combined with two cutting frequencies and three warming scenarios: no warming, +3.0/+3.0 and +2.2/+4.0°C (day/night) atmospheric warming. The elevated CO2 treatment increased both new and net root length production primarily when combined with atmospheric warming, where the constant warming treatment had a greater positive effect than the increased night‐time warming treatment. Responses to elevated CO2 were greater when the swards were cut more frequently and responsiveness varied with season. For Phalaris swards, 17% of total net primary productivity went belowground. On account of root turnover, only one‐third of the new roots produced in the year following establishment could be expected, on average, to be recovered from soil cores. The interaction between the effects of CO2 and warming, combined with the differential effects of the two warming treatments, has important implications for modelling belowground responses to projected climate change.
Predicting adaptive evolution under elevated atmospheric CO2 in the perennial grass Bromus erectus
Authors: STEINGER THOMAS , STEPHAN ANDRÉ , SCHMID BERNHARD
Published: April 2007

Increasing concentrations of CO2 in the atmosphere are likely to affect the ecological dynamics of plant populations and communities worldwide, yet little is known about potential evolutionary consequences of high CO2. We employed a quantitative genetic framework to examine how the expression of genetic variation and covariation in fitness‐related traits, and thus, the evolutionary potential of a species, is influenced by CO2. In two field experiments, genotypes of the dominant grassland perennial Bromus erectus were grown for several years in plots maintained at present‐day or at elevated CO2 levels. Under noncompetitive conditions (experiment 1), elevated CO2 had little impact on plant survival, growth, and reproduction. Under competitive conditions in plots with diverse plant communities (experiment 2), performance of B. erectus was reduced by elevated CO2. This suggests that the effect of CO2 was largely indirect, intensifying competitive interactions. Elevated CO2 had significant effects on the expression of genetic variation in both the competitive and noncompetitive environment, but the effects were in opposite direction. Heritability of plant size was generally higher at elevated than at ambient CO2 in the noncompetitive environment, but lower in the competitive environment. Selection analysis revealed a positive genotypic selection differential for plant size at ambient CO2, indicating selection favoring genotypes with high growth rate. At elevated CO2, the corresponding selection differential was nonsignificant and slightly negative. This suggests that elevated CO2 is unlikely to stimulate the evolution of high biomass productivity in this species.
Shift in birch leaf metabolome and carbon allocation during long‐term open‐field ozone exposure
Authors: KONTUNEN‐SOPPELA SARI , OSSIPOV VLADIMIR , OSSIPOVA SVETLANA , OKSANEN ELINA
Published: April 2007

Current and future ozone concentrations have the potential to reduce plant growth and increase carbon demand for defence and repair processes, which may result in reduced carbon sink strength of forest trees in long‐term. Still, there is limited understanding regarding the alterations in plant metabolism and variation in ozone tolerance among tree species and genotypes. Therefore, this paper aims to study changes in birch leaf metabolome due to long‐term realistic ozone stress and to relate these shifts in the metabolism with growth responses. Two European white birch (Betula pendula Roth) genotypes showing different ozone sensitivity were growing under 1.4–1.7 × ambient ozone in open‐field conditions in Central Finland. After seven growing seasons, the trees were analysed for changes in leaf metabolite profiling, based on 339 low molecular weight compounds (including phenolics, polar and lipophilic compounds, and pigments) and related whole‐tree growth responses. Genotype caused most of the variance of metabolite concentrations, while ozone concentration was the second principal component explaining the metabolome profiling. The main ozone caused changes included increases in quercetin‐phenolic compounds and compounds related to leaf cuticular wax layer, whereas several compounds related to carbohydrate metabolism and function of chloroplast membranes and pigments (such as chlorophyll‐related phytol derivatives) were decreasing. Some candidate compounds such as surface wax‐related squalene, 1‐dotriacontanol, and dotriacontane, providing growth‐related tolerance against ozone were demonstrated. This study indicated that current growth‐based ozone risk assessment methods are inadequate, because they ignore ecophysiological impacts due to alterations in leaf chemistry.
Effects of nutrient addition on vegetation and carbon cycling in an ombrotrophic bog
Authors: BUBIER JILL L. , MOORE TIM R. , BLEDZKI LESZEK A.
Published: April 2007

We measured net ecosystem CO2exchange (NEE), plant biomass and growth, species composition, peat microclimate, and litter decomposition in a fertilization experiment at Mer Bleue Bog, Ottawa, Ontario. The bog is located in the zone with the highest atmospheric nitrogen deposition for Canada, estimated at 0.8–1.2 g N m−2 yr−1(wet deposition as NH4and NO3). To establish the effect of nutrient addition on this ecosystem, we fertilized the bog with six treatments involving the application of 1.6–6 g N m−2 yr−1(as NH4NO3), with and without P and K, in triplicate 3 m × 3 m plots. The initial 5–6 years have shown a loss of firstSphagnum, thenPolytrichummosses, and an increase in vascular plant biomass and leaf area index. Analyses of NEE, measuredin situwith climate‐controlled chambers, indicate that contrary to expectations, the treatments with the highest levels of nutrient addition showed lower rates of maximum NEE and gross photosynthesis, but little change in ecosystem respiration after 5 years. Although shrub biomass and leaf area increased in the high nutrient plots, loss of moss photosynthesis owing to nutrient toxicity, increased vascular plant shading and greater litter accumulation contributed to the lower levels of CO2uptake. Our study highlights the importance of long‐term experiments as we did not observe lower NEE until the fifth year of the experiment. However, this may be a transient response as the treatment plots continue to change. Higher levels of nutrients may cause changes in plant composition and productivity and decrease the ability of peatlands to sequester CO2from the atmosphere.
The relative importance of landscape properties for woodland birds in agricultural environments
Authors: RADFORD JAMES Q , BENNETT ANDREW F
Published: April 2007

Studies of landscape change are seldom conducted at scales commensurate with the processes they purport to investigate. Landscape change is a landscape‐level process, yet most studies focus on patches. Even when landscape context is considered, inference remains at the patch‐level. The unit of investigation must be extended beyond individual patches to whole mosaics in order to advance understanding of faunal responses to landscape change.

In this study, we aggregated data from multiple sites per landscape such that both the response and explanatory variables characterized ‘whole’ landscapes, allowing for landscape‐level inference about factors influencing species’ incidence.

We used hierarchical partitioning and Bayesian variable selection methods to develop species‐specific models that examined the influence of four categories of landscape properties – habitat extent, habitat configuration, landscape composition and geographical location – on the incidence of 58 species of woodland‐dependent birds in 24 agricultural landscapes (each 100 km2) in south‐eastern Australia.

There was strong evidence for a positive effect of habitat extent for 27 species. Thirty species were related to at least one of the four landscape composition variables, and geographical location was important for 19 species. Habitat configuration was influential for 13 species and where important, the impacts of fragmentation per se were detrimental.

Variation among species in the influential landscape variables indicates that different species respond to different sets of cues in land mosaics. Thus, although all species were grouped a priori as ‘woodland‐dependent’, expectations based on general ecological characteristics may prove unreliable.

Synthesis and applications. These results underscore the value of moving beyond the fragmentation paradigm focused on the spatial pattern of habitat vs. non‐habitat, to a greater appreciation of the composition and heterogeneity of land mosaics. Landscape‐level inference will enable improved conservation outcomes by recognizing the influence of landscape properties on biota and devising strategies at this scale to complement patch‐based management. We provide strong empirical evidence that biodiversity management in agricultural landscapes must focus on habitat extent. Complementary management of other landscape attributes, such as habitat aggregation and intensity of agricultural land‐use, will also enhance the value of agricultural landscapes for woodland birds.