Influences of population density,temperature and latitude on the growth of invasive topmouth gudgeon Pseudorasbora parva          下载免费PDF全文

Gareth D. Davies  J. Robert Britton 《Ecology of Freshwater Fish》2015,24(1):91-98

Plasticity in life‐history traits provides advantages for introduced fish in overcoming demographic bottlenecks that would otherwise inhibit establishment. Here, the influence of population density, temperature and latitude was tested on the growth increments and growth rates of invasive populations of topmouth gudgeon Pseudorasbora parva, a small Asian cyprinid fish that is invasive across Europe. Aquaria experiments tested the roles of fish number and temperature on growth increments under a fixed food supply, pond experiments tested the role of density on growth increments, and a field study completed in England and Wales tested the influence of density and latitude on growth rates. In aquaria experiments, whilst growth increments were higher at 21 and 23 °C than at 19 and 25 °C, fish number had a greater influence on growth than temperature. Higher growth increments were produced at lower densities. In experimental ponds, growth increments were significantly higher in ponds with low densities of P. parva compared with those at elevated densities. In the field study comprising 10 wild populations across a latitudinal gradient of 4.0°N, a difference in mean air temperatures of approximately 3 °C, and estimated densities between 0.5 and 65.0 m^?2, population density was the only significant predictor of growth rates. Whilst populations at very low densities comprised of significantly faster growing individuals, there were no significant differences when densities were between 15 and 65 m^?2. Thus, invasive P. parva populations have considerable growth plasticity, especially at low densities, with this likely to be important in their ability to colonise new environments.  相似文献   

Successful treatment of severe hypokalemia in a dog with acute kidney injury caused by leptospirosis          下载免费PDF全文

Ashley E. Allen DVM  Gareth J. Buckley MA  VetMB  DACVECC  DECVECC  Michael Schaer DVM  DACVIM  DACVECC 《Journal of Veterinary Emergency and Critical Care》2016,26(6):837-843

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Scanning Electron Microscopic and Immunohistochemical Study of Uterine and Placental Vascularization in the Rat During Different Stages of Pregnancy     

E. Betti    M. Zeiler    R. Leiser    V. Dantzer    C. Pfarrer 《Anatomia, histologia, embryologia》2005,34(S1):5-6

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Caesarean sections in cows     

Mulligan G 《The Veterinary record》2003,152(5):148

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Can Batesian mimicry help plants to deter herbivores?     

Massei G  Cotterill JV  Coats JC  Bryning G  Cowan DP 《Pest management science》2007,63(6):559-563

Several authors have suggested that edible plants could avoid herbivory by mimicking olfactory cues of toxic plants. However, very few studies have been carried out to test this hypothesis. The aims of the present study were to identify the volatiles of three clover species and to test whether a species lacking chemical defences, such as red clover, could avoid being grazed by rabbits by mimicking the volatiles of the cyanogenic white clover. Two main volatiles were identified in all three clover species, and a further two volatiles were present in white clover only. Rabbits presented with a choice between white clover, red clover and red clover sprayed with white clover extract ate significantly more red clover than white or white-flavoured red clover. The results suggest that the volatiles of toxic plants could be used and exploited as a source of natural, safe and effective repellents to control the impact of pest herbivores on plants.  相似文献   

Long-term catch trends and risk assessment of the Critically Endangered white-spotted wedgefish (Rhynchobatus djiddensis) from South Africa     

Ryan Daly  Denham Parker  Geremy Cliff  Gareth L. Jordaan  Nkabi Nomfundo  Rhett H. Bennett  Bruce Q. Mann 《水产资源保护:海洋与淡水生态系统》2021,31(4):777-788

1. The white-spotted wedgefish (Rhynchobatus djiddensis) is a Critically Endangered shark-like ray in the family Rhinidae. Throughout its Western Indian Ocean distribution, it is targeted for its valuable meat and fins and is reported to have undergone major population declines. However, there remains a need for species specific time-series data to accurately assess localized population declines.
2. This study used two independent long-term (37 and 40 years) time-series catch data from competitive shore angling and shark nets to investigate the size composition and catch per unit effort (CPUE) and conduct a risk assessment for the population on the east coast of South Africa.
3. From 1977 to 2017 the competitive shore fishery captured 7,703 individual R. djiddensis, whilst shark nets in the same region captured 2,856 individuals from 1981 to 2017. Individuals captured in the nets had a sex ratio of 1.8:1 females to males, and were larger than those caught by the anglers. Although the mean annual sizes of net-caught individuals were above the size of reported sexual maturity, there was little evidence to suggest that any individuals captured were reproductively active.
4. Both the competitive shore fishery and shark net catches exhibited strong seasonal trends with the majority of R. djiddensis catches occurring from October to May peaking in austral summer. Standardized CPUE from the competitive shore fishery declined substantially between 1977 and 2017 and shark net catches exhibited a significant (p < 0.05) fourfold decline in annual nominal CPUE from 1981 to 2017.
5. Ultimately, a risk assessment showed a 65.1% decline in abundance over a period of three generation lengths, which indicates that the sampled population of R. djiddensis in South Africa should be classified as Endangered according to the IUCN Red List using criterion A2b. The conservation implications of this are discussed.

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Estimating the component of soil respiration not dependent on living plant roots: Comparison of the indirect y-intercept regression approach and direct bare plot approach     

Georgia R. Koerber  Paul W. Hill  Gareth Edwards-Jones  David L. Jones 《Soil biology & biochemistry》2010,42(10):1835-1841

Distinguishing between root and non-root derived CO₂ efflux is important when determining rates of soil organic matter turnover, however, in practice they remain difficult to separate. Our aim was to evaluate two methods for determining the component of below-ground respiration not dependent on plant roots (i.e., basal soil respiration; R_b). The first approach estimated R_b indirectly from the y-intercept of linear regressions between below-ground respiration (BGR) and root biomass. The second approach involved direct measurements of soil respiration from bare plots. To compare the contrasting approaches, BGR and crop biomass measurements were collected throughout the year in a range of agricultural systems. We found that both methods were very closely correlated with each other. Values of R_b determined by the intercept approach, however, were slightly higher than those determined by measurement of bare plots. Both approaches showed a seasonal trend with estimates of R_b lowest in winter months at 0.02 t C ha⁻¹ month⁻¹ for the y-intercept approach and 0.11 t C ha⁻¹ month⁻¹ for the bare plots approach, even after the data had been corrected for the influence of soil temperature. Highest rates of R_b occurred from the height to the end of the crop growing season (0.8-1.5 t C ha⁻¹ month⁻¹). The annual CO₂ efflux due to R_b was estimated to be 8.1 t C ha⁻¹ y⁻¹ from the y-intercept approach and 6.8 t C ha⁻¹ y⁻¹ from bare plots. Annual BGR was 12.1 t C ha⁻¹ y⁻¹. We conclude that both methods provide similar estimates of R_b, however, logistically the bare plots approach is much easier to undertake than the y-intercept approach.  相似文献   

Dispersal of woody plants in forest edges and hedgerows in a Southern Swedish agricultural area: the role of site and landscape structure     

Sarlöv Herlin  Ingrid L.  Fry  Gareth L.A. 《Landscape Ecology》2000,15(3):229-242

The distribution of woody vegetation was studied in forest edges and hedgerows in a 28 km² southern Swedish agricultural area, characterised by species-rich edge zones. The occurrence of 21 selected woody species (taxa) was related to differences in both edge structure and landscape structure. All the species studied were represented in both edge types, but a higher frequency of animal-dispersed species was found in hedgerows.Animal dispersed species were more affected by edge width and density than wind dispersed species. A higher number of wind-dispersed species were more frequent in forest edges, in hedgerows near to forest, or with a high proportion of forest within 500 m. A clear relationship was found between the number of physically connected elements in hedgerow networks and increasing frequency of occurrence for Corylus avellana, Crataegus spp., Euonymus europaeus, and Quercus robur; which indicate the ecological significance of connectedness for certain animal dispersed species. The study supports the general principle that woody species distribution and landscape structure are linked in a positive feedback loop. The results match findings from studies in other countries and are interpreted in the context of landscape processes and the ecological characteristics of woody plant species. We emphasise the importance of understanding dispersal mechanisms of woody species for the design and improvement of edge habitats in agricultural landscapes.  相似文献   

Anthelmintic use in goats     

Edwards GT  Mitchell ES  Harwood DG 《The Veterinary record》2007,161(22):763-764

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Revisiting the taxonomic impediment     

de Carvalho MR  Bockmann FA  Amorim DS  de Vivo M  de Toledo-Piza M  Menezes NA  de Figueiredo JL  Castro RM  Gill AC  McEachran JD  Compagno LJ  Schelly RC  Britz R  Lundberg JG  Vari RP  Nelson G 《Science (New York, N.Y.)》2005,307(5708):353

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