Vascular plant changes in extreme environments: effects of multiple drivers

The Antarctic Peninsula is one of three regions of the planet that have experienced the highest rates of climate warming over recent decades. Based on a comprehensive large-scale resurvey, allowing comparison of new (2009) and historical data (1960s), we show that the two native Antarctic vascular plant species have exhibited significant increases in number of occupied sites and percent cover since the 1960s: Deschampsia antarctica increasing in coverage by 191 % and in number of sites by 104 %. Colobanthus quitensis increasing in coverage by 208 % and number of sites by 35 %. These changes likely occurred in response to increases of 1.2 °C in summer air temperature over the same time period. Both species exhibited changes with elevation due to the interaction of multiple drivers (climatic factors and animal disturbance), producing heterogeneity of responses across an elevation gradient. Below an elevation of 20 m fur seal activity exerted negative impacts. Between 20 and 60 m, both plant species underwent considerable increases in the number of sites and percent cover, likely influenced by both climate warming and nutrient input from seals. Above an elevation threshold of 60 m the maximum elevation of the sites occupied decreased for both species, perhaps as a consequence of physical disturbance at higher elevations due to the permafrost conditions and/or the snow cover thickness and persistence. Understanding the role of disturbance drivers for vegetation change in cold regions may become a research priority to enable improved forecasting of biological responses and feedbacks of climate warming on ecosystems in these globally influential regions

Pseudogap formation of four-layer BaRuO3_3 and its electrodynamic response changes

We investiaged the optical properties of four-layer BaRuO$_{3}$, which shows a fermi-liquid-like behavior at low temperature. Its optical conductivity spectra clearly displayed the formation of a pseudogap and the development of a coherent peak with decreasing temperature. Temperature-dependences of the density $n$ and the scattering rate $1/\tau$ of the coherent component were also derived. As the temperature decreases, both $n$ and $1/\tau$ decrease for four-layer BaRuO$_{3}$. These electrodynamic responses were compared with those of nine-layer BaRuO$_{3}$, which also shows a pseudogap formation but has an insulator-like state at low temperature. It was found that the relative rates of change of both $n$ and $1/\tau$ determine either metallic or insulator-like responses in the ruthenates. The optical properties of the four-layer ruthenate were also compared with those of other pseudogap systems, such as high $T_{c}$ cuprates and heavy electron systems.Comment: 7 figures. submitted to Phys. Rev.

On the complete classification of the unitary N=2 minimal superconformal field theories

Aiming at a complete classification of unitary N=2 minimal models (where the assumption of space-time supersymmetry has been dropped), it is shown that each modular invariant candidate of a partition function for such a theory is indeed the partition function of a minimal model. A family of models constructed via orbifoldings of either the diagonal model or of the space-time supersymmetric exceptional models demonstrates that there exists a unitary N=2 minimal model for every one of the allowed partition functions in the list obtained from Gannon's work. Kreuzer and Schellekens' conjecture that all simple current invariants can be obtained as orbifolds of the diagonal model, even when the extra assumption of higher-genus modular invariance is dropped, is confirmed in the case of the unitary N=2 minimal models by simple counting arguments.Comment: 53 pages; Latex; minor changes in v2: intro expanded, references added, typos corrected, footnote added on p31; renumbering of sections; main theorem reformulated for clarity, but contents unchanged. Minor revisions in v3: typos corrected, footnotes 5, 6 added, lemma 1 and section 3.3.2 rewritten for greater generality, section 3.3 review removed. To appear in Comm. Math. Phy

Neutrino Interferometry In Curved Spacetime

Gravitational lensing introduces the possibility of multiple (macroscopic) paths from an astrophysical neutrino source to a detector. Such a multiplicity of paths can allow for quantum mechanical interference to take place that is qualitatively different to neutrino oscillations in flat space. After an illustrative example clarifying some under-appreciated subtleties of the phase calculation, we derive the form of the quantum mechanical phase for a neutrino mass eigenstate propagating non-radially through a Schwarzschild metric. We subsequently determine the form of the interference pattern seen at a detector. We show that the neutrino signal from a supernova could exhibit the interference effects we discuss were it lensed by an object in a suitable mass range. We finally conclude, however, that -- given current neutrino detector technology -- the probability of such lensing occurring for a (neutrino-detectable) supernova is tiny in the immediate future.Comment: 25 pages, 1 .eps figure. Updated version -- with simplified notation -- accepted for publication in Phys.Rev.D. Extra author adde

Limited Lifespan of Fragile Regions in Mammalian Evolution

An important question in genome evolution is whether there exist fragile regions (rearrangement hotspots) where chromosomal rearrangements are happening over and over again. Although nearly all recent studies supported the existence of fragile regions in mammalian genomes, the most comprehensive phylogenomic study of mammals (Ma et al. (2006) Genome Research 16, 1557-1565) raised some doubts about their existence. We demonstrate that fragile regions are subject to a "birth and death" process, implying that fragility has limited evolutionary lifespan. This finding implies that fragile regions migrate to different locations in different mammals, explaining why there exist only a few chromosomal breakpoints shared between different lineages. The birth and death of fragile regions phenomenon reinforces the hypothesis that rearrangements are promoted by matching segmental duplications and suggests putative locations of the currently active fragile regions in the human genome

Geographic Variation In Resource Dominance Discovery In Brazilian Ant Communities

A predictive framework for the ecology of species invasions requires that we learn what limits successful invaders in their native range. The red imported fire ant (Solenopsis invicta) is invasive in the United States, Puerto Rico, Australia, New Zealand, and China, Solenopsis invicta appears to be a superior competitor in its introduced range, where it can cause the local extirpation of native species, but little is known about its competitive ability in its native range in South America. Here we examine the competitive ability of S. invicta for food resources in three widely separated Brazilian ant communities. Each of these communities contains 20-40 ant species, 8-10 of which were common and frequently interacted with S. invicta. S. invicta at all three sites was attacked by several species-specific phorid parasitoids, and at one site, two other species were attacked by their own specialized parasitoids. We examined interactions in these local communities for evidence that trade-offs among ant species between resource dominance and resource discovery, and between resource dominance and parasitoid vulnerability facilitate local coexistence. The trade-off between resource dominance and resource discovery was strong and significant only at Santa Genebra, where parasitoids had no effect on the outcome of confrontations at resources. At Bonito, parasitoids significantly reduced the ability of S. invicta, which was the top-ranked behavioral dominant, from defending and usurping food resources from subordinate species. In the Pantanal, S. invicta ranked behind three other ant species in a linear hierarchy of behavioral dominance, and lost the majority of its interactions with a fourth more subordinate species, Paratrechina fulva, another invasive species. Parasitoids of S. invicta were uncommon in the Pantanal, and did not affect its low position in the hierarchy relative to the other two sites. Parasitoids, however, did affect the ability of Linepithema angulation, the top-ranked behavioral dominant in this community, from defending and usurping resources from behavioral subordinates. These results indicate that both interspecific competition and trait-mediated indirect effects of phorid parasitoids affect the ecological success of the red imported fire ant in its native range, but that the relative importance of these factors varies geographically. © 2008 by the Ecological Society of America.89718241836Adler, F.R., The balance of terror: An alternative mechanism for competitive tradeoffs and its implications for invading species (1999) American Naturalist, 154, pp. 497-509Adler, F.R., LeBrun, E.G., Feener Jr., D.H., Maintaining diversity in an ant community: Modeling, extending, and testing the dominance-discovery trade-off (2007) American Naturalist, 169, pp. 323-333Allen, C.R., Lutz, R.S., Demaris, S., Red imported fire ant impacts on northern bobwhite populations (1995) Ecological Applications, 5, pp. 632-638Allen, C.R., Willey, R.D., Myers, P.E., Horton, P.M., Buffa, J., Impact of red imported fire ant infestation on northern bobwhite quail abundance trends in southeastern United States (2000) Journal of Agricultural and Urban Entomology, 17, pp. 43-51Bestelmeyer, B.T., The trade-off between thermal tolerance and behavioural dominance in a subtropical South American ant community (2000) Journal of Animal Ecology, 69, pp. 998-1009Callaway, R.M., Aschehoug, E.T., Invasive plants versus their new and old neighbors: A mechanism for exotic invasion (2000) Science, 290, pp. 521-523Cerdá, X., Retana, J., Cros, S., Thermal disruption of transitive hierarchies in Mediterranean ant communities (1997) Journal of Animal Ecology, 66, pp. 363-374Cerdá, X., Retana, J., Cros, S., Critical thermal limits in Mediterranean ant species: Trade-off between mortality risk and foraging performance (1998) Functional Ecology, 12, pp. 45-55Cerdá, X., Retana, J., Manzaneda, A., The role of competition by dominants and temperature in the foraging of subordinate species in mediterranean ant communities (1998) Oecologia, 117, pp. 404-412Chase, J.M., Abrams, P.A., Grover, J.P., Diehl, S., Chesson, P., Holt, R.D., Richards, S.A., Case, T.J., The interaction between predation and competition: A review and synthesis (2002) Ecology Letters, 5, pp. 302-315Chase, J.M., Leibold, M.A., (2003) Ecological niches: Linking classical and contemporary approaches, , University of Chicago Press, Chicago, Illinois, USAColley, W.N., (2002) Colley's bias free college football ranking method: The Colley matrix explained, , http://www.colleyrankings.com/matrate.pdfCytel. 2005. StatXact. Version 7. Cytel, Cambridge, Massachusetts, USADavidson, D.W., Resource discovery versus resource domination in ants: A functional mechanism for breaking the trade-off (1998) Ecological Entomology, 23, pp. 484-490de Vries, H., An improved test of linearity in dominance hierarchies containing unknown or tied relationships (1995) Animal Behaviour, 50, pp. 1375-1389de Vries, H., Finding a dominance order most consistent with a linear hierarchy: A new procedure and review (1998) Animal Behaviour, 55, pp. 827-843de Vries, H., Netto, W.J., Hanegraaf, P.L.H., MatMan: A program for the analysis of sociometric matrices and behavioral transition matrices (1993) Behaviour, 125, pp. 157-175Feener Jr., D.H., Is the assembly of ant communities mediated by parasitoids? (2000) Oikos, 90, pp. 79-88Fellers, J.H., Interference and exploitation in a guild of woodland ants (1987) Ecology, 68, pp. 1466-1478Folgarait, P.J., D'Adamo, P., Gilbert, L.E., A grassland ant community in Argentina: The case of Solenopsis richteri and Camponotus punctulatus (Hymenoptera: Formicidae) attaining high densities in their native ranges (2004) Annals of the Entomological Society of America, 97, pp. 450-457Giraud, T., Pedersen, J.S., Keller, L., Evolution of supercolonies: The Argentine ants of southern Europe (2002) Proceedings of the National Acadcmv of Sciences, 99, pp. 6075-6079. , USAHölldobler, B., Wilson, E.O., (1990) The ants, , Harvard University Press, Cambridge, Massachusetts, USAHolway, D.A., Effect of Argentine ant invasions on ground-dwelling arthropods in northern California riparian woodlands (1998) Oecologia, 116, pp. 252-258Holway, D.A., Competitive mechanisms underlying the displacement of native ants by the invasive Argentine ant (1999) Ecology, 80, pp. 238-251Holway, D.A., Lach, L., Suarez, A.V., Tsutsui, N.D., Case, T.J., The causes and consequences of ant invasions (2002) Annual Review of Ecology and Systematics, 33, pp. 181-233Hook, A.W., Porter, S.D., Destruction of harvester ant colonies by invading fire ants in South-central Texas (Hymenoptera: Formicidae) (1990) Southwestern Naturalist, 35, pp. 477-478Keane, R.M., Crawley, M.J., Exotic plant invasions and the enemy release hypothesis (2002) Trends in Ecology and Evolution, 17, pp. 164-170Kneitel, J.M., Chase, J.M., Trade-offs in community ecology: Linking spatial scales and species coexistence (2004) Ecology Letters, 7, pp. 69-80Kopachena, J.G., Buckley, A.J., Potts, G.A., Effects of the red imported fire ant (Solenopsis invicta) on reproductive success of barn swallows (Hirundo rustica) in northeast Texas (2000) Southwestern Naturalist, 45, pp. 477-482LeBrun, E.G., Who is the top dog in ant communities? Resources, parasitoids, and multiple competitive hierarchies (2005) Oecologia, 142, pp. 643-652LeBrun, E.G., Feener, D.H., Linked indirect effects in ant-phorid interactions: Impacts on ant assemblage structure (2002) Oecologia, 133, pp. 599-607LeBrun, E.G., Feener, D.H., When trade-offs interact: Balance of terror enforces dominance discovery-trade-off in a local ant assemblage (2007) Journal of Animal Ecology, 76, pp. 58-64LeBrun, E.G., Tillberg, C.V., Suarez, A.V., Folgarait, P., Smith, C.R., Holway, D.A., An experimental study of competitive interactions between red imported fire ants and Argentine ants in a region of native-range sympatry (2007) Ecology, 88, pp. 63-75Lockwood, J.L., McKinney, M.L., (2001) Biotic homogenization, , Kluwer Academic Publishers, New York, New York, USALodge, D.M., Biological invasions: Lessons for ecology (1993) Trends in Ecology and Evolution, 8, pp. 133-137Mann, C.C., Fire ants parlay their queens into a threat to biodiversity (1994) Science, 263, pp. 1560-1561Mattos, M.R., Orr, M.R., Two new species of Pseudacteon (Diptera: Phoridae) of ants in the genus Linepithema (Hymenoptera: Formicidae) in Brazil (2002) Studia Dipterologia, 9, pp. 283-288Mescher, M.C., Ross, K.G., Shoemaker, D.D., Keller, L., Krieger, M.J.B., Distribution of the two social forms of the fire ant Solenopsis invicta (Hymenoptera: Formicidae) in the native South American range (2003) Annals of the Entomological Society of America, 96, pp. 810-817Morrison, L.W., Community organization in a recently assembled fauna: The case of Polynesian ants (1996) Oecologia, 107, pp. 243-256Morrison, L.W., Long-term impacts of an arthropod-community invasion by the imported fire ant, Solenopsis invicta (2002) Ecology, 83, pp. 2337-2345Morrison, L.W., Kawazoe, E.A., Guerra, R., Gilbert, L.E., Ecological interactions of Pseudacteon parasitoids and Solenopsis ant hosts: Environmental correlates of activity and effects on competitive hierarchies (2000) Ecological Entomology, 25, pp. 433-444Noldus Information Technology, 2002. MatMan. Version 1.1. Noldus Information Technology, Sterling, Virginia, USAOlden, J.D., Poff, N.L., Toward a mechanistic understanding and prediction of biotic homogenization (2003) American Naturalist, 162, pp. 442-460Olden, J.D., Poff, N.L., Ecological processes driving biotic homogenization: Testing a mechanistic model using fish faunas (2004) Ecology, 85, pp. 1867-1875Orr, M.R., Dahlsten, D.L., Benson, W.W., Ecological interactions among ants in the genus Linepithema, their parasitoids (Diptera: Phoridae), and their ant competitors (2003) Ecological Entomology, 28, pp. 203-210Orr, M.R., Seike, S.H., Gilbert, L.E., Foraging ecology and patterns of diversification in dipteran parasitoids of fire ants in south Brazil (1997) Ecological Entomology, 22, pp. 305-314Porter, S.D., Fowler, H.G., Mackay, W.P., Fire ant mound densities in the United States and Brazil (Hymenoptera: Formicidae) (1992) Journal of Economic Entomology, 85, pp. 1154-1161Porter, S.D., Savignano, D.A., Invasion of polygyne fire ants decimates native ants and disrupts arthropod community (1990) Ecology, 71, pp. 2095-2106Porter, S.D., Williams, D.F., Patterson, R.S., Fowler, H.G., Intercontinental differences in the abundance of Solenopsis fire ants (Hymenoptera: Formicidae): an escape from natural enemies? (1997) Environmental Entomology, 26, pp. 373-384Qian, H., Ricklefs, R.E., The role of exotic species in homogenizing the North American flora (2006) Ecology Letters, 9, pp. 1293-1298R Development Core Team. 2006. R: a language and environment for statistical computing. Version 2.3.1. R Foundation for Statistical Computing, Vienna, AustriaRetana, J., Cerdá, X., Patterns of diversity and composition of Mediterranean ground ant communities tracking spatial and temporal variability in the thermal environment (2000) Oecologia, 123, pp. 436-444Ross, K.G., Vargo, E.L., Keller, L., Social evolution in a new environment: The case of introduced fire ants (1996) Proceedings of the National Academy of Sciences (USA), 93, pp. 3021-3025Seike, S.H., (2002) Ecologica da interaçáo entre formigas invasoras e moscas parasitóides, , Dissertation. Universidade Estadual de Campinas, Campinas, BrazilShea, K., Chesson, P., Community ecology theory as a framework for biological invasions (2002) Trends in Ecology and Evolution, 17, pp. 170-176Trager, J.C., A revision of the fire ants, Solenopsis geminata group (Hymenoptera: Formicidae: Myrmicinae) (1991) Journal of the New York Entomological Society, 99, pp. 141-198Tschinkel, W.R., Distribution of the fire ants Solenopsis invicta and S. geminata (Hymenoptera: Formicidae) in northern Florida in relation to habitat and disturbance (1988) Annals of the Entomological Society of America, 81, pp. 76-81Tschinkel, W.R., (2006) The fire ants, , Belknap Press, Cambridge, Massachusetts, USATsutsui, N.D., Suarez, A.V., Holway, D.A., Case, T.J., Reduced genetic variation and the success of an invasive species (2000) Proceedings of the National Academy of Sciences (USA), 97, pp. 5948-5953Vepsäläinen, K., Pisarski, B., Assembly of island ant communities (1982) Annales Zoologici Fennici, 19, pp. 327-335Wolfe, L.M., Why alien invaders succeed: Support for the escape-from-enemv hypothesis (2002) American Naturalist, 160, pp. 705-71

Economics of Quality of Experience

International audienc

The distorted body: the perception of the relative proportions of the body is preserved in Parkinson’s disease

Given humans’ ubiquitous visual experience of their own body, one reasonable assumption is that one’s perceptions of the lengths of their body parts should be accurate. However, recent research has shown that large systematic distortions of the length of body parts are present in healthy younger adults. These distortions appear to be linked to tactile sensitivity such that individuals overestimate the length of body parts of low tactile sensitivity to a greater extent than body parts of high tactile sensitivity. There are certain conditions featuring reduced tactile sensitivity, such as Parkinson’s Disease (PD) and healthy older ageing. However, the effect of these circumstances on individuals’ perceptions of the lengths of their body parts remains unknown. In this study, participants visually estimated the length of their body parts using their hand as a metric. We show that despite the reductions in tactile sensitivity, and potential alterations in the cortical presentation of body parts that may occur in PD and healthy older ageing, individuals with mild-moderate PD and older adults of comparable age experience body size distortions comparable to healthy younger controls. These findings demonstrate that the ability to perceive the length of one’s body parts is well preserved in mild-moderate PD

Designing a broad-spectrum integrative approach for cancer prevention and treatment

Targeted therapies and the consequent adoption of "personalized" oncology have achieved notablesuccesses in some cancers; however, significant problems remain with this approach. Many targetedtherapies are highly toxic, costs are extremely high, and most patients experience relapse after a fewdisease-free months. Relapses arise from genetic heterogeneity in tumors, which harbor therapy-resistantimmortalized cells that have adopted alternate and compensatory pathways (i.e., pathways that are notreliant upon the same mechanisms as those which have been targeted). To address these limitations, aninternational task force of 180 scientists was assembled to explore the concept of a low-toxicity "broad-spectrum" therapeutic approach that could simultaneously target many key pathways and mechanisms. Using cancer hallmark phenotypes and the tumor microenvironment to account for the various aspectsof relevant cancer biology, interdisciplinary teams reviewed each hallmark area and nominated a widerange of high-priority targets (74 in total) that could be modified to improve patient outcomes. For thesetargets, corresponding low-toxicity therapeutic approaches were then suggested, many of which werephytochemicals. Proposed actions on each target and all of the approaches were further reviewed forknown effects on other hallmark areas and the tumor microenvironment. Potential contrary or procar-cinogenic effects were found for 3.9% of the relationships between targets and hallmarks, and mixedevidence of complementary and contrary relationships was found for 7.1%. Approximately 67% of therelationships revealed potentially complementary effects, and the remainder had no known relationship. Among the approaches, 1.1% had contrary, 2.8% had mixed and 62.1% had complementary relationships. These results suggest that a broad-spectrum approach should be feasible from a safety standpoint. Thisnovel approach has potential to be relatively inexpensive, it should help us address stages and types ofcancer that lack conventional treatment, and it may reduce relapse risks. A proposed agenda for futureresearch is offered