11,221 research outputs found
Conservation Pakage for Modal Ecorace
Conserving biodiversity is about genetic variety, species, habitats and ecosystems. All are important, but it is often most appropriate, practical and effective to focus on species. With modern conservation awareness, there is a welcome and popular commitment to maintaining the diversity of species in India. Nevertheless, over the last 50 years, we have witnessed the severe decline of many once widespread and familiar species, such as tropical Tasar silkworm Antherea mylitta D. Conservation is not just about avoiding extinctions, but about restoring or recovering species populations to secure levels and preventing other species from reaching such a perilous situation in the first place. Species, by their very nature, have specific ecological requirements. They may appear to share the same habitat with many others but each has a different, specific niche. It is what sets them apart, and makes them what they are. Habitat loss has historically been a factor in species decline. However, the way existing habitats are managed is also important
Species of Bursaphelenchus Fuchs, 1937 (Nematoda: Parasitaphelenchidae) and other nematode genera associated with insects from Pinus pinaster in Portugal
Insects associated with maritime pine, Pinus pinaster, in Portugal were collected
and screened for the presence of Bursaphelenchus species. Nematodes were
identified using Internal Transcribed Spacers-Restriction Fragment Length
Polymorphism (ITS-RFLP) analysis of dauer juveniles and morphological
identification of adults that developed from dauer juveniles on fungal cultures
or on cultures in pine wood segments at 26 C. Several associations are
described: Bursaphelenchus teratospicularis and Bursaphelenchus sexdentati are
associated with Orthotomicus erosus; Bursaphelenchus tusciae, B. sexdentati and/or
Bursaphelenchus pinophilus with Hylurgus ligniperda and Bursaphelenchus hellenicus
with Tomicus piniperda, Ips sexdentatus and H. ligniperda. An unidentified
Bursaphelenchus species is vectored by Hylobius sp. The previously reported
association of Bursaphelenchus xylophilus with Monochamus galloprovincialis
was confirmed. The association of Bursaphelenchus leoni with Pityogenes sp. is
not definitively established and needs further studies for clarification.
Other nematode genera besides Bursaphelenchus were found to be associated
with the insects sampled, including two different species of Ektaphelenchus, Parasitorhabditis
sp., Parasitaphelenchus sp., Contortylenchus sp. and other unidentified
nematodes. The Ektaphelenchus species found in O. erosus is morphologically
similar to B. teratospicularis found in the same insect; adults of both the species
are found in cocoon-like structures under the elytra of the insects.
Introduction
Approximately one third of the nematodes belonging to
the order Aphelenchida Siddiqi, 1980 are associated with
insects (Poinar, 1983). These nematodes establish a variety
of associations with the insects, which may be
described as commensalism, e.g. phoresy (to the benefit
of the nematode but not affecting the insect), mutualism
(both the organisms benefit) or parasitism (nematodes
benefit at the expense of the insect) (Giblin-Davis,
2004).
Most Bursaphelenchus Fuchs, 1937 species are mycetophagous,
feeding on fungi in the galleries of bark beetles
and thu
New Frontiers in Cosmology and Galaxy Formation: Challenges for the Future
(Abridged) Cosmology faces three distinct challenges in the next decade. (1)
The dark sector, both dark matter and dark energy, dominates the Universe. Key
questions include determining the nature of both. Improved observational probes
are crucial. (2) Galaxy formation was initiated at around the epoch of
reionization: we need to understand how and when as well as to develop probes
of earlier epochs. (3) Our simple dark matter-driven picture of galaxy assembly
is seemingly at odds with several observational results, including the presence
of ULIRGS at high z, the `downsizing' signature, chemical signatures of
alpha-element ratios and suggestions that merging may not be important in
defining the Hubble sequence. Understanding the physical implications is a
major challenge for theorists and refiniing the observational uncertainties a
major goal for observers.Comment: To appear in "Structure Formation in the Universe", ed. Chabrier, G.,
Cambridge University Press. High resolution version on
http://www.astro.caltech.edu/~rse/chamonix.pd
Leaf Mining Insects and Their Parasitoids in the Old-Growth Forest of the Huron Mountains
Leaf mining insects in an old-growth forest along the south central shore of Lake Superior in Michigan are documented. We present the results of a 13-year survey of leaf mining species, larval hosts, seasonal occurrence, and parasitoids, as well as report biological observations. Representative larvae, mines, adults, and parasitoids were preserved. Among the larval host associations, 15 are reported as new. Additionally, 42 parasitoid taxa were identified resulting in six first reports from the New World and 32 new host associations. Two undescribed species (Gelechiidae and Figitidae) discovered through this research were described in earlier publications
3-D Models of Embedded High-Mass Stars: Effects of a Clumpy Circumstellar Medium
We use 3-D radiative transfer models to show the effects of clumpy
circumstellar material on the observed infrared colors of high mass stars
embedded in molecular clouds. We highlight differences between 3-D clumpy and
1-D smooth models which can affect the interpretation of data. We discuss
several important properties of the emergent spectral energy distribution
(SED): More near-infrared light (scattered and direct from the central source)
can escape than in smooth 1-D models. The near- and mid-infrared SED of the
same object can vary significantly with viewing angle, depending on the clump
geometry along the sightline. Even the wavelength-integrated flux can vary with
angle by more than a factor of two. Objects with the same average circumstellar
dust distribution can have very different near-and mid-IR SEDs depending on the
clump geometry and the proximity of the most massive clump to the central
source.
Although clumpiness can cause similar objects to have very different SEDs,
there are some observable trends. Near- and mid-infrared colors are sensitive
to the weighted average distance of clumps from the central source and to the
magnitude of clumpy density variations (smooth-to-clumpy ratio). Far-infrared
emission remains a robust measure of the total dust mass. We present simulated
SEDs, colors, and images for 2MASS and Spitzer filters. We compare to
observations of some UCHII regions and find that 3-D clumpy models fit better
than smooth models. In particular, clumpy models with fractal dimensions in the
range 2.3-2.8, smooth to clumpy ratios of <50%, and density distributions with
shallow average radial density profiles fit the SEDs best.Comment: accepted to ApJ; version with full-res figures:
http://www.astro.virginia.edu/~ri3e/clumpy3d.pd
On the origin of X-shaped radio-sources: new insights from the properties of their host galaxies
A significant fraction of extended radio sources presents a peculiar X-shaped
radio morphology: in addition to the classical double lobed structure, radio
emission is also observed along a second axis of symmetry in the form of
diffuse wings or tails. We re-examine the origin of these extensions relating
the radio morphology to the properties of their host galaxies. The orientation
of the wings shows a striking connection with the structure of the host galaxy
as they are preferentially aligned with its minor axis. Furthermore, wings are
only observed in galaxies of high projected ellipticity. Hydrodynamical
simulations of the radio-source evolution show that X-shaped radio-sources
naturally form in this geometrical situation: as a jet propagates in a
non-spherical gas distribution, the cocoon surrounding the radio-jets expands
laterally at a high rate producing wings of radio emission, in a way that is
reminiscent of the twin-exhaust model for radio-sources.Comment: 7 pages, 6 figures, 1 table, accepted for publication in A&
1.4-GHz observations of extended giant radio galaxies
This paper presents 1.4-GHz radio continuum observations of 15 very extended
radio galaxies. These sources are so large that most interferometers lose
partly their structure and total flux density. Therefore, single-dish
detections are required to fill in the central (u,v) gap of interferometric
data and obtain reliable spectral index patterns across the structures, and
thus also an integrated radio continuum spectrum. We have obtained such 1.4-GHz
maps with the 100-m Effelsberg telescope and combined them with the
corresponding maps available from the NVSS. The aggregated data allow us to
produce high-quality images, which can be used to obtain physical parameters of
the mapped sources. The combined images reveal in many cases extended low
surface-brightness cocoons.Comment: 39 pages, 19 figures, 3 tables. Published in Ac
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