185 research outputs found
Reptiles and frogs conform to multiple conceptual landscape models in an agricultural landscape
Aim
Effective management of biodiversity in human-modified landscapes demands an understanding of how biotas respond to landscape features and management actions. Yet, biotic responses are complex and varied, resulting in numerous conceptual models being developed to aid interpretation and generalization. We examined the relevance of a range of conceptual landscape models that describe how the distribution of habitat influences species richness, abundance, occurrence and spatial dynamics, using an empirical data set of reptile and frog responses to agricultural management.
Location
South-eastern New South Wales, Australia.
Methods
We tested predictions developed from five conceptual landscape models using data collected from five land cover types and two grazing regimes.
Results
At least one species responded in a manner consistent with each of the five conceptual models tested. Most species responded to gradients of environmental variables and species-specific responses were observed, in congruence with the Continuum model. No species were consistently congruent with predictions from concepts of Island Biogeography theory. One-third of responses were congruent with the Matrix Quality model. The main prediction tested from the Matrix Tolerance model was upheld by both reptile and frog species. The predictions of the Habitat Amount hypothesis were upheld by rare reptile abundance and richness, and one frog species.
Main conclusions
Our study suggests that most conceptual models have some relevance to real-world systems and can be useful for interpreting biotic responses to landscape change and management. Importantly, no one model fully captured the range of species responses to our agricultural landscape, but the Continuum model, Matrix Quality model, Matrix Tolerance model and Habitat Amount hypothesis had complementary predictions that together appeared to explain most of the assemblage's responses to the management and environmental conditions of the agricultural landscape.We thank the Environmental Trust (NSW) and Lesslie Endowment for
funding this research along with the support of the Fenner School of
Environment and Society. SAP was supported by an Australian
Government Research Training Program (RTP) Scholarship
OSETI with STACEE: A Search for Nanosecond Optical Transients from Nearby Stars
We have used the STACEE high-energy gamma-ray detector to look for fast
blue-green laser pulses from the vicinity of 187 stars. The STACEE detector
offers unprecedented light-collecting capability for the detection of
nanosecond pulses from such lasers. We estimate STACEE's sensitivity to be
approximately 10 photons per square meter at a wavelength of 420 nm. The stars
have been chosen because their characteristics are such that they may harbor
habitable planets and they are relatively close to Earth. Each star was
observed for 10 minutes and we found no evidence for laser pulses in any of the
data sets.Comment: 38 pages, 12 figures. Accepted for publication in Astrobiolog
Nuclear Spin-Isospin Correlations, Parity Violation, and the Problem
The strong interaction effects of isospin- and spin-dependent nucleon-nucleon
correlations observed in many-body calculations are interpreted in terms of a
one-pion exchange mechanism. Including such effects in computations of nuclear
parity violating effects leads to enhancements of about 10%. A larger effect
arises from the one-boson exchange nature of the parity non-conserving nucleon-
nucleon interaction, which depends on both weak and strong meson-nucleon
coupling constants. Using values of the latter that are constrained by
nucleon-nucleon phase shifts leads to enhancements of parity violation by
factors close to two. Thus much of previously noticed discrepancies between
weak coupling constants extracted from different experiments can be removed.Comment: 8 pages 2 figures there should have been two figures in v
Very high energy observations of the BL Lac objects 3C 66A and OJ 287
Using the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), we
have observed the BL Lac objects 3C 66A and OJ 287. These are members of the
class of low-frequency-peaked BL Lac objects (LBLs) and are two of the three
LBLs predicted by Costamante and Ghisellini to be potential sources of very
high energy (>100 GeV) gamma-ray emission. The third candidate, BL Lacertae,
has recently been detected by the MAGIC collaboration. Our observations have
not produced detections; we calculate a 99% CL upper limit of flux from 3C 66A
of 0.15 Crab flux units and from OJ 287 our limit is 0.52 Crab. These limits
assume a Crab-like energy spectrum with an effective energy threshold of 185
GeV.Comment: 24 pages, 15 figures, Accepted for publication in Astroparticle
Physic
Reservoir-host amplification of disease impact in an endangered amphibian
Emerging wildlife pathogens are an increasing threat to biodiversity. One of the most serious wildlife diseases is chytridiomycosis, caused by the fungal pathogen, Batrachochytrium dendrobatidis (Bd), which has been documented in over 500 amphibian species. Amphibians vary greatly in their susceptibility to Bd; some species tolerate infection, whereas others experience rapid mortality. Reservoir hosts-species that carry infection while maintaining high abundance but are rarely killed by disease-can increase extinction risk in highly susceptible, sympatric species. However, whether reservoir hosts amplify Bd in declining amphibian species has not been examined. We investigated the role of reservoir hosts in the decline of the threatened northern corroboree frog (Pseudophryne pengilleyi) in an amphibian community in southeastern Australia. In the laboratory, we characterized the response of a potential reservoir host, the (nondeclining) common eastern froglet (Crinia signifera), to Bd infection. In the field, we conducted frog abundance surveys and Bd sampling for both P. pengilleyi and C. signifera. We built multinomial logistic regression models to test whether Crinia signifera and environmental factors were associated with P. pengilleyi decline. C. signifera was a reservoir host for Bd. In the laboratory, many individuals maintained intense infections (>1000 zoospore equivalents) over 12 weeks without mortality, and 79% of individuals sampled in the wild also carried infections. The presence of C. signifera at a site was strongly associated with increased Bd prevalence in sympatric P. pengilleyi. Consistent with disease amplification by a reservoir host, P. pengilleyi declined at sites with high C. signifera abundance. Our results suggest that when reservoir hosts are present, population declines of susceptible species may continue long after the initial emergence of Bd, highlighting an urgent need to assess extinction risk in remnant populations of other declined amphibian species.Funding was provided by the Australian Academy of Science and a Taronga Zoo Field Conservation Grant. B.
Scheele was supported by Australian Research Council grant LP110200240 during the revisions of this
manuscript
Short- and long- term effects of habitat fragmentation differ but are predicted by response to the matrix
Habitat loss and fragmentation are major threats to biodiversity and ecosystem
processes. Our current understanding of the impacts of habitat loss and fragmentation is based
largely on studies that focus on either short- term or long- term responses. Short- term responses
are often used to predict long- term responses and make management decisions. The lack of
studies comparing short- and long- term responses to fragmentation means we do not adequately
understand when and how well short- term responses can be extrapolated to predict long- term
responses, and when or why they cannot. To address this gap, we used data from one of the
worldâs longest- running fragmentation experiments, The Wog Wog Habitat Fragmentation
Experiment. Using data for carabid beetles, we found that responses in the long term (more
than 22 yr post- fragmentation â22 generations) often contrasted markedly with those in the
short term (5 yr post- fragmentation). The total abundance of all carabids, species richness and
the occurrence of six species declined in the short term in the fragments but increased over the
long term. The occurrence of three species declined initially and continued to decline, whilst
another species was positively affected initially but decreased in the long term. Speciesâ
responses to the matrix that surrounds the fragments strongly predicted both the direction
(increase/decline in occurrence) and magnitude of their responses to fragmentation.
Additionally, speciesâ responses to the matrix were somewhat predicted by their preferences for
different types of native habitat (open vs. shaded). Our study highlights the degree of the
matrixâs influence in fragmented landscapes, and how this influence can change over time. We
urge caution in using short- term responses to forecast long- term responses in cases where the
matrix (1) impacts speciesâ responses to fragmentation (by isolating them, creating new habitat
or altering fragment habitat) and (2) is likely to change through time.Funding to collect, process and identify samples between 2009 and 2013 was provided by
NSF DEB 0841892 to KFD and BAM. KFD was also supported by NSF DEB 1350872. MJE was funded by an Australian
National University PhD Scholarship
Managing uncertainty in movement knowledge for environmental decisions.
Species' movements affect their response to environmental change but movement knowledge is often highly uncertain. We now have well-established methods to integrate movement knowledge into conservation practice but still lack a framework to deal with uncertainty in movement knowledge for environmental decisions. We provide a framework that distinguishes two dimensions of species' movement that are heavily influenced by uncertainty: knowledge about movement and relevance of movement to environmental decisions. Management decisions can be informed by their position in this knowledge-relevance space. We then outline a framework to support decisions around (1) increasing understanding of the relevance of movement knowledge, (2) increasing robustness of decisions to uncertainties and (3) improving knowledge on species' movement. Our decision-support framework provides guidance for managing movement-related uncertainty in systematic conservation planning, agri-environment schemes, habitat restoration and international biodiversity policy. It caters to different resource levels (time and funding) so that species' movement knowledge can be more effectively integrated into environmental decisions
Thermodynamic Description of the Relaxation of Two-Dimensional Euler Turbulence Using Tsallis Statistics
Euler turbulence has been experimentally observed to relax to a
metaequilibrium state that does not maximize the Boltzmann entropy, but rather
seems to minimize enstrophy. We show that a recent generalization of
thermodynamics and statistics due to Tsallis is capable of explaining this
phenomenon in a natural way. The maximization of the generalized entropy
for this system leads to precisely the same profiles predicted by the
Restricted Minimum Enstrophy theory of Huang and Driscoll. This makes possible
the construction of a comprehensive thermodynamic description of Euler
turbulence.Comment: 15 pages, RevTe
CDMS, Supersymmetry and Extra Dimensions
The CDMS experiment aims to directly detect massive, cold dark matter
particles originating from the Milky Way halo. Charge and lattice excitations
are detected after a particle scatters in a Ge or Si crystal kept at ~30 mK,
allowing to separate nuclear recoils from the dominating electromagnetic
background. The operation of 12 detectors in the Soudan mine for 75 live days
in 2004 delivered no evidence for a signal, yielding stringent limits on dark
matter candidates from supersymmetry and universal extra dimensions. Thirty Ge
and Si detectors are presently installed in the Soudan cryostat, and operating
at base temperature. The run scheduled to start in 2006 is expected to yield a
one order of magnitude increase in dark matter sensitivity.Comment: To be published in the proceedings of the 7th UCLA symposium on
sources and detection of dark matter and dark energy in the universe, Marina
del Rey, Feb 22-24, 200
Relationship between structural pathology and pain behaviour in a model of osteoarthritis (OA)
Objectives
To address the hypothesis that different types of established OA pain behaviours have associations with different aspects of articular pathology, we investigated the relationship between structural knee joint pathology and pain behaviour following injection of a low versus a high dose of monosodium iodoacetate (MIA) in the rat.
Methods
Rats received a single intra-articular injection of 0.1mg or 1mg MIA or saline (control). Pain behaviour (hind limb weight bearing asymmetry (WB) and hindpaw withdrawal threshold (PWT) to punctate stimulation) was assessed. Cartilage and synovium were examined by macroscopic visualisation of articular surfaces and histopathology.
Results
Both doses of MIA lowered PWTs, 1mg MIA also resulted in WB asymmetry. Both doses were associated with cartilage macroscopic appearance, proteoglycan loss, abnormal chondrocyte morphology, increased numbers of vessels crossing the osteochondral junction, synovitis and macrophage infiltration into the synovium. PWTs were more strongly associated with chondrocyte morphology, synovitis and macrophage infiltration than with loss of cartilage surface integrity.
Conclusions
Both pain behaviours were associated with OA structural severity and synovitis. Differences in pain phenotype following low versus higher dose of MIA were identified despite similar structural pathology. OA structural pathology as traditionally measured only partially explains the MIA-induced pain phenotype
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