636 research outputs found
Habitat requirements and conservation needs of peripheral populations : the case of the great crested newt (Triturus cristatus) in the Scottish Highlands
Edge populations are of conservation importance because of their roles as reservoirs of evolutionary potential and in understanding a given speciesâ ecological needs. Mainly due to loss of aquatic breeding sites, the great crested newt Triturus cristatus is amongst the fastest declining amphibian species in Europe. Focusing on the north-westerly limit of the T. cristatus range, in the Scottish Highlands, we aimed to characterise habitat requirements and conservation needs of an isolated set of edge populations. We recorded 129 breeding-pond related environmental parameters, and used a variable-selection procedure followed by random forest analysis to build a predictive model for the speciesâ present occurrence, as well as for population persistence incorporating data on population losses. The most important variables predicting T. cristatus occurrence and persistence were associated with pond quality, pond shore and surrounding terrestrial habitat (especially mixed Pinus sylvestris - Betula woodland), and differed from those identified in the speciesâ core range. We propose that habitat management and pond creation should focus on the locally most favourable habitat characteristics to improve the conservation status and resilience of populations. This collaborative work, between conservation agencies and scientific researchers, is presented as an illustrative example of linking research, management and conservation
SuDS and amphibians - are constructed wetlands really benefitting nature and people?
While urbanisation is a major threat to global
biodiversity, it also brings opportunities for some
species. Sustainable Drainage Systems (SuDS) have
been installed in all Scottish cities to reduce flood
and pollution risk and they can also offer new
habitats for wildlife. We studied SuDS in Inverness
and the Scottish Central Belt to assess their value as
amphibian breeding sites, habitats, and as places
where urban people can experience nature. The
nine-year study revealed that many SuDS were of
similar ecological quality to wider countryside ponds
but that the quality of ponds is not equitably
distributed between neighbourhoods inhabited by
different socio-economic classes. However, the
findings suggest ways to improve the design and
management of SuDS for people and nature, making
access to high quality ponds available to all social
groups
Geographic variation in life-history traits : growth season affects age structure, egg size and clutch size in Andrewâs toad (Bufo andrewsi)
Background: Environmental variation associated with season length is likely to promote differentiation in lifehistory
traits, but has been little studied in natural populations of ectotherms. We investigated patterns of variation
in egg size, clutch size, age at sexual maturity, maximum age, mean age, growth rate and adult body size in
relation to growth season length among 17 populations of Andrewâs toad (Bufo andrewsi) at different latitudes and
altitudes in the Hengduan Mountains, western China.
Results: We found that egg size, age at sexual maturity, and mean age increased with decreasing length of the
growth season, whereas clutch size showed a converse cline. Body size did not increase with decreasing length of
the growth season, but was tightly linked to lifetime activity (i.e. the estimated number of active days during
lifetime). Males and females differed in their patterns of geographic variation in growth rates, which may be the
result of forces shaping the trade-off between growth and reproduction in different environments.
Conclusions: Our findings suggest that growth season plays an important role in shaping variation in life-history
traits in B. andrewsi across geographical gradients
Toll-like receptor variation in the bottlenecked population of the Seychelles warbler: computer simulations see the âghost of selection pastâ and quantify the âdrift debtâ
Balancing selection can maintain immunogenetic variation within host populations, but detecting its signal in a post-bottlenecked population is challenging due to the potentially overriding effects of drift. Toll-like receptor genes (TLRs) play a fundamental role in vertebrate immune defence and are predicted to be under balancing selection. We previously characterised variation at TLR loci in the Seychelles warbler (Acrocephalus sechellensis), an endemic passerine that has undergone a historical bottleneck. Five out of seven TLR loci were polymorphic, which is in sharp contrast to the low genome-wide variation observed. However standard population genetic statistical methods failed to detect a contemporary signature of selection at any TLR loci. We examined whether the observed TLR polymorphism could be explained by neutral evolution, simulating the population's demography in the software DIYABC. This showed that the posterior distributions of mutation rates had to be unrealistically high to explain the observed genetic variation. We then conducted simulations with an agent-based model using typical values for the mutation rate, which indicated that weak balancing selection has acted on the three TLR genes. The model was able to detect evidence of past selection elevating TLR polymorphism in the pre-bottleneck populations, but was unable to discern any effects of balancing selection in the contemporary population. Our results show drift is the overriding evolutionary force that has shaped TLR variation in the contemporary Seychelles warbler population, and the observed TLR polymorphisms might be merely the âghost of selection pastâ. Forecast models predict immunogenetic variation in this species will continue to be eroded in the absence of contemporary balancing selection. Such âdrift debtâ occurs when a genepool has not yet reached its new equilibrium level of polymorphism, and this loss could be an important threat to many recently bottlenecked populations
Effekten av olika koncentrationer av Rotstop R och Rotstop S och ofullstÀndig tÀckning av Rotstop S pÄ sporinfektioner av rotticka pÄ granstubbar
The effectiveness of treatment with two Phlebiopsis gigantea based preparations (RotstopÂź
and RotstopS) in different concentrations against the root and butt rot causing fungus
Heterobasidion annosum s.l. on Norway spruce (Picea abies) thinning stumps in southern
Sweden was compared. The trees were cut on three sites during the summer 2004 and 285
stumps were treated manually with 100% cover with two different amounts of spores in
solution corresponding to approximately 5Ă106 spores/l and 10Ă106 spores/l. 31 stumps
received mechanical part cover with the highest spore concentrations of Phlebiopsis gigantea, i.e. approximately 20Ă106 spores/l. Mechanical treatment was assessed for satisfactory treatment effect. Three months later, samples were collected and analyzed.
There was a significant reduction in frequency and relative areas of Heterobasidion spp.
infections on stumps with manual application of control agents compared to untreated stumps. On average 10 to 23% of stumps subjected to manual treatments were infected compared to 52% for the untreated stumps. However, none of the concentration solutions of RotstopŸ and RotstopS differed from the others in reduction of Heterobasidion spp. infections. Mechanical treatment failed to control the Heterobasidion spp. infections, but there was a tendency for the 85.1-95.0% cover class to provide better result than the others. Thus, despite of the incomplete control of the pathogen, stump treatment with different concentrations of Phlebiopsis gigantea oidia in suspensions provided equal effects at the present spore loads of Heterobasidion spp.Effektiviteten av behandling med tvÄ pergamentsvampsbaserade (Phlebiopsis gigantea)
lösningar (RotstopŸ och RotstopS) i olika koncentrationer mot sporinfektioner av rotticka
(Heterobasidion spp.) pÄ gallringsstubbar av gran (Picea abies) i södra Sverige jÀmfördes.
TrÀd avverkades pÄ tre olika lokaler under sommaren 2004 och sammanlagt 285 stubbar
behandlades manuellt med en hundraprocentig tÀckning i tvÄ olika koncentrationer
motsvarande ungefĂ€r 5Ă106 sporer/l respektive 10Ă106 sporer/l lösning. 31 stubbar pĂ„ en av
lokalerna behandlades maskinellt med en ofullstÀndig tÀckning men med den högsta
koncentrationen av pergamentsvamp (RotstopS), ca 20Ă106 sporer/l lösning. Effekten av den
mekaniska behandlingens partiella tÀckning jÀmfördes med den manuella fullstÀndiga. Tre
mÄnader efter behandlingen samlades prover in för analys med avseende pÄ förekomsten av
rotticka.
Alla manuella behandlingar gav en signifikant reducering av frekvensen av och relativa arean
av rottickeinfektioner jÀmfört med obehandlade stubbar. I genomsnitt var 10 till 23 % av de
manuellt behandlade stubbarna infekterade jÀmfört med 52 % av de obehandlade. Ingen av de
manuella applikationerna skiljde sig dock frÄn varandra. Den mekaniska behandlingen gav
inte ett tillfredsstÀllande resultat men det fanns en tendens till att tÀckningsgradsklass 85,1-
95,0 % fungerade bÀttre Àn de andra. SÄledes, trots att ingen behandling gav en 100 % -ig
minskning av antalet rottickeinfektioner, verkar olika koncentrationer av RotstopÂź och
RotstopS ge ett likvÀrdigt resultat under de förhÄllanden i sportryck som rÄdde vid
behandlingen
Current and future water balance for coupled human-natural systems â Insights from a glacierized catchment in Peru
Study region
Santa River basin, Peru.
Study focus
In the Andes of Peru, climate change and socio-economic development are expected to jeopardize future water availability. However, little is known about the interplay of multiple climatic and non-climatic stressors and related processes driving water resource changes. We developed an integrated model that analyzes different trajectories of water availability including hydro-climatic (water supply) and socio-economic (water demand) variables with consistent multi-descriptor future scenarios until 2050.
New hydrological insights for the region
At the lower-basin outflow of Condorcerro, mean annual water availability is projected to increase by 10% ± 12% by 2050. This gain is mainly driven by an increase in annual precipitation amounts of about 14% (RCP2.6) and 18% (RCP8.5), respectively, which was computed using a global climate multi-model ensemble. In contrast, mean dry-season water availability is projected to substantially decrease by 33% and 36% ( ± 24%) by 2050, for RCP2.6 and RCP8.5, respectively. This decline is driven by a combination of diminishing glacier discharge and increasing water demand both of which adopt a major role in the absence of considerable precipitation inputs. These seasonal differences highlight the need to adequately consider spatiotemporal scales within multi-scenario water balance models to support local decision-making. Our results elucidate the need for improvements in water management and infrastructure to counteract diminishing dry-season water availability and to reduce future risks of water scarcity
How did the toad get over the sea to Skye? Tracing the colonisation of Scottish inshore islands by common toads (Bufo bufo)
Processes of island colonisation have long been of interest to biologists. Colonisation events themselves are rarely observed, but the processes involved may be inferred using genetic approaches. We investigated possible means of island colonisation by common toads (Bufo bufo) in western Scotland (the Isle of Skye and five neighbouring small islands), using evidence derived from nuclear microsatellites and mitochondrial (mt) DNA. Levels of microsatellite allelic richness for populations on Skye were high and comparable to adjacent mainland populations, but lower for populations on small islands. Pairwise measures of genetic distances between populations and a clustering algorithm were both suggestive of frequent gene flow between Skye and the mainland. For small islands the levels of genetic differentiation were higher, implying stronger isolation and no evidence for inbreeding. The distribution of mtDNA haplotypes broadly mirrored the genetic structure revealed by microsatellites. Reconciled with existing palaeoclimatological evidence, since the last glaciation, our findings rule out the possibility that the B. bufo populations stem from glacial refugia, or that recent anthropogenic transfer of toads is responsible for their current distribution. The most parsimonious explanation of our data is that the studied inshore islands have been repeatedly colonised via rafting from the mainland or neighbouring islands. This may give us insights into the processes likely to take place when ice sheets retreat poleward as a result of climate change. It also has implications for the colonisation of
both native and invasive non-native species, and hence the biosecurity of island refugia
A toy model of the five-dimensional universe with the cosmological constant
A value of the cosmological constant in a toy model of the five-dimensional
universe is calculated in such a manner that it remains in agreement with both
astronomical observations and the quantum field theory concerning the
zero-point fluctuations of the vacuum. The (negative) cosmological constant is
equal to the inverse of the Planck length squared, which means that in the toy
model the vanishing of the observed value of the cosmological constant is a
consequence of the existence of an energy cutoff exactly at the level of the
Planck scale. In turn, a model for both a virtual and a real
particle-antiparticle pair is proposed which describes properly some energetic
properties of both the vacuum fluctuations and created particles, as well as it
allows one to calculate the discrete "bare" values of an elementary-particle
mass, electric charge and intrinsic angular momentum (spin) at the energy
cutoff. The relationships between the discussed model and some phenomena such
as the Zitterbewegung and the Unruh-Davies effect are briefly analyzed, too.
The proposed model also allows one to derive the Lorentz transformation and the
Maxwell equations while considering the properties of the vacuum filled with
the sea of virtual particles and their antiparticles. Finally, the existence of
a finite value of the vacuum-energy density resulting from the toy model leads
us to the formulation of dimensionless Einstein field equations which can be
derived from the Lagrangian with a dimensionless (naively renormalized)
coupling constant.Comment: 52 pages, 1 figure; a post-final, rewritten version with a number of
new remarks and conclusion
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