Impact of biodiversity-climate futures on primary production and metabolism in a model benthic estuarine system     

Natalie Hicks  Mark T Bulling  Martin Solan  Dave Raffaelli  Piran CL White  David M Paterson 《BMC ecology》2011,11(1):1-8

Background

A territory as a prerequisite for breeding limits the maximum number of breeders in a given area, and thus lowers the proportion of breeders if population size increases. However, some territorially breeding animals can have dramatic density fluctuations and little is known about the change from density-dependent processes to density-independence of breeding during a population increase or an outbreak. We suggest that territoriality, breeding suppression and its break-down can be understood with an incomplete-control model, developed for social breeders and social suppression.

Results

We studied density dependence in an arvicoline species, the bank vole, known as a territorial breeder with cyclic and non-cyclic density fluctuations and periodically high densities in different parts of its range. Our long-term data base from 38 experimental populations in large enclosures in boreal grassland confirms that breeding rates are density-regulated at moderate densities, probably by social suppression of subordinate potential breeders. We conducted an experiment, were we doubled and tripled this moderate density under otherwise the same conditions and measured space use, mortality, reproduction and faecal stress hormone levels (FGM) of adult females. We found that mortality did not differ among the densities, but the regulation of the breeding rate broke down: at double and triple densities all females were breeding, while at the low density the breeding rate was regulated as observed before. Spatial overlap among females increased with density, while a minimum territory size was maintained. Mean stress hormone levels were higher in double and triple densities than at moderate density.

Conclusions

At low and moderate densities, breeding suppression by the dominant breeders, But above a density-threshold (similar to a competition point), the dominance of breeders could not be sustained (incomplete control). In our experiment, this point was reached after territories could not shrink any further, while the number of intruders continued to increase with increasing density. Probably suppression becomes too costly for the dominants, and increasing number of other breeders reduces the effectiveness of threats. In wild populations, crossing this threshold would allow for a rapid density increase or population outbreaks, enabling territorial species to escape density-dependency.  相似文献   

A comparison of anesthetic risk factors and outcomes in light and draft horses     

CB  Riley †  DH Riedesel  ‡  IR Dohoo†  CL Hatfield†  S Clinch† 《Veterinary anaesthesia and analgesia》2003,30(2):113-114

As a result of anatomic and physiologic differences, draft breeds may be at greater risk of developing anesthetic complications. The aim of the study was to evaluate and compare anesthetic management of draft (DR) and light (LT) horses. A case‐matched retrospective study of 371 clinical case records of DR (124 cases) and LT (247 cases) horses presented for general anesthesia between 1991 and 1998 was performed. Data were tabulated and comparisons were made using Student's t‐test (significance p < 0.05). Prior to induction, there were significant differences in mean body weight, rectal temperature, PCV, RBC, and serum TP concentration between DR and LT breeds. There were differences in mean doses of pre‐operative butorphanol (LT 21 µg kg^?1; DR 17 µg kg^?1), induction guaifenesin (LT 99 mg kg^?1; DR 88 mg kg^?1), and intraoperative ketamine (LT 0.35 mg kg^?1; DR 0.56 mg kg^?1) required. There were no significant differences in the mean doses of pre‐operative xylazine, detomidine, or induction barbiturate administered. The mean, average, and maximum concentrations of inspired halothane were significantly higher for DR than for LT horses. Draft horses received 33% less intraoperative IV fluids (8.2 mL kg^?1 hour^?1) than LT horses. Mean anesthetic duration, time to extubation, and standing recovery were not significantly different. Induction complications were not reported for either group. Rates of occurrence of intraoperative bradycardia, hypercarbia, hypoxemia, and metabolic acidosis (SBE, TCO₂, and bicarbonate concentration) did not differ significantly. Average MAP was greater in DR horses, but neither the degree nor the mean duration of hypotension differed between DR and LT horses. Mean PaO₂ was significantly lower in DR (246 mm Hg, 32.8 kPa) than in LT (305 mm Hg, 40.7 kPa) breeds. Draft horses were at greater relative risk of hypoventilation than LT horses. The greater MAP and requirement for halothane and intraoperative ketamine may indicate problems in achieving and maintaining a surgical plane of anesthesia. Draft horses may be at a greater risk of ventilation–perfusion mismatching.  相似文献   

Annual variation of hematology and plasma chemistry in shortnose sturgeon, Acipenser brevirostrum, during a dam-impeded spawning run     

Mark A. Matsche  Jarrett Gibbons 《Fish physiology and biochemistry》2012,38(6):1679-1696

Shortnose sturgeon (Acipenser brevirostrum) spawning migrations on the Cooper River are impeded by Pinopolis Dam, Lake Moultrie, South Carolina. Sturgeon and other species aggregate below the dam in late winter/early spring and are subjected to a variety of stressors stemming from crowding, poor habitat quality, and injuries that appear to be caused by boat propeller or turbine strikes. Spawning has been documented in the tailrace, but reproductive success has not been verified as no juveniles have been captured. Fish within the dam tailrace were captured by gill net during winter, 2005 and 2007–2011, and physiological condition was assessed using a panel of hematologic and biochemical indices. Plasma phosphorus and calcium were significantly higher in females, while PCV and aspartate aminotransferase were significantly higher in males, indicating sex-specific physiological changes triggered during maturity. A marked leucopenia, accompanied by lymphopenia and neutrophilia, was evident in both sexes and was consistent across years, indicating that these fish were under chronic stress. Testosterone and estradiol levels and hematologic and biochemical reference intervals are provided for comparative purposes.  相似文献   

Selection and characterization of resistance to the Vip3Aa20 protein from Bacillus thuringiensis in Spodoptera frugiperda          下载免费PDF全文

Oderlei Bernardi  Daniel Bernardi  Renato J Horikoshi  Daniela M Okuma  Leonardo L Miraldo  Julio Fatoretto  Fernanda CL Medeiros  Tony Burd  Celso Omoto 《Pest management science》2016,72(9):1794-1802

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Motivations for Enrollment Into the Conservation Reserve Enhancement Program in the James River Basin of South Dakota     

Jarrett Pfrimmer  Larry Gigliotti  Joshua Stafford  David Schumann  Katie Bertrand 《Human Dimensions of Wildlife》2017,22(4):382-389

The Conservation Reserve Enhancement Program (CREP) targets high-priority conservation needs (e.g., water quality, wildlife habitat) by paying landowners an annual rental rate to remove environmentally sensitive or agriculturally unproductive lands from rowcrop production, and then implement conservation practices on these lands. This study examined motivations of South Dakota landowners for enrolling in the James River Basin CREP. All 517 newly enrolled landowners were mailed a questionnaire in 2014 measuring demographics, behaviors, opinions, and motivations (60% response rate). Cluster analysis of 10 motivations for enrolling identified three motivation groups (wildlife = 40%, financial = 35%, environmental = 25%). The financial group had the youngest mean age (62 years), followed by the wildlife (65) and environmental groups (68). Among respondents, 43% favored the public access requirement of this CREP with the environmental group most in favor. Understanding landowner enrollment motivations and decision criteria will assist in strategies (e.g., financial incentives, increasing yield via habitat restoration) for increasing future participation.  相似文献   

Suppressive subtractive hybridization analysis of Rhipicephalus (Boophilus) microplus larval and adult transcript expression during attachment and feeding     

Ala E. Lew-Tabor  Paula M. Moolhuijzen  Megan E. Vance  Sebastian Kurscheid  Manuel Rodriguez Valle  Sandra Jarrett  Catherine M. Minchin  Louise A. Jackson  Nick N. Jonsson  Matthew I. Bellgard  Felix D. Guerrero 《Veterinary parasitology》2010,167(2-4):304-320

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A new transmissible agent causing acute hepatitis, chronic hepatitis and cirrhosis in dogs   总被引：1，自引：0，他引：1  

W F Jarrett  B W O'Neil 《The Veterinary record》1985,116(24):629-635

There is a hepatitis of dogs which occurs in acute, persistent and chronic forms. Histological studies of spontaneous cases suggested that several apparently diverse hepatic diseases might be stages of one process. This was also implied by follow up studies and case histories: acute non-lethal episodes were followed later by the development of chronic hepatitis, cirrhosis and liver failure. Serum was taken and homogenates of liver were made from three field cases representing different putative temporal stages of the complex. These were injected into experimental dogs and a hepatitis was induced in all. The cytopathological and histological changes were the same in all animals and were identical to field cases. Acute lethal disease and persistent infections were produced. Two second passages were carried out and an identical condition was induced, characterised by recurrent episodes of subclinical hepatitis and persistent infection. It is suggested that the disease might be named canine acidophil cell hepatitis in view of the pathognomonic cytopathology. Specific morphological criteria have been established for this hepatitis.  相似文献   

Field trials of a formulation containing moxidectin and 6 in 1 vaccines for sheep     

CL SCHWARTZKOFF  RM COBB 《Australian veterinary journal》1996,74(3):225-227

Objective: To assess the efficacy and safety of a formulation containing moxidectin and 6 in 1 vaccine in sheep under field conditions.
Design: Efficacy and safety study.
Animals: Two hundred and five crossbred Merino lambs and two hundred and eight Merino ewes were used in the studies.
Procedure: A formulation was made for the simultaneous treatment of sheep with moxidectin and immunisation against clostridial diseases and caseous lymphadenitis. The efficacy against nematodes, vaccine response and safety were assessed.
Results: Effective control of nematodes and responses to antigens were achieved following subcutaneous administration. The formulation was safe to administer; occasional minor tissue reactions were evident, but no other adverse effects of treatment were observed in either pregnant ewes or lambs, using either the recommended dose, or an overdose of the formulation.
Conclusion: Administration of a formulation containing moxidectin, five clostridial antigens and caseous lymphadenitis antigen proved safe and efficacious under field conditions.  相似文献   

Are endogenous feline leukemia viruses really endogenous?     

Stewart H  Jarrett O  Hosie MJ  Willett BJ 《Veterinary immunology and immunopathology》2011,143(3-4):325-331

Full length endogenous feline leukemia virus (FeLV) proviruses exist within the genomes of many breeds of domestic cat raising the possibility that they may also exist in a transmissible exogenous form. Such viruses would share receptor usage with the recombinant FeLV-B subgroup, a viral subgroup that arises in vivo by recombination between exogenous subgroup A virus (FeLV-A) and endogenous FeLV. Accordingly, all isolates of FeLV-B made to date have contained a "helper" FeLV-A, consistent with their recombinatorial origin. In order to assess whether endogenous viruses are transmitted between cats, we examined primary isolates of FeLV for which the viral subgroup had been determined for the presence of a subgroup B virus that lacked an FeLV-A. Here we describe the identification of two primary field isolates of FeLV (2518 and 4314) that appeared to contain subgroup B virus only by classical interference assays, raising the possibility of between-host transmission of endogenous FeLV. Sequencing of the env gene and U3 region of the 3' long terminal repeat (LTR) confirmed that both viral genomes contained endogenous viral env genes. However the viral 3' LTRs appeared exogenous in origin with a putative 3' recombination breakpoint residing at the 3' end of the env gene. Further, the FeLV-2518 virions also co-packaged a truncated FeLV-A genome containing a defective env gene, termed FeLV-2518(A) whilst no helper subgroup A viral genome was detected in virions of FeLV-4314. The acquisition of an exogenous LTR by the endogenous FeLV in 4314 may have allowed a recombinant FeLV variant to outgrow an exogenous FeLV-A virus that was presumably present during first infection. Given time, a similar evolution may also occur within the 2518 isolate. The data suggest that endogenous FeLVs may be mobilised by acquisition of exogenous LTRs yielding novel viruses that type biologically as FeLV-B.  相似文献   

Team assembly mechanisms determine collaboration network structure and team performance   总被引：1，自引：0，他引：1  

Guimerà R  Uzzi B  Spiro J  Amaral LA 《Science (New York, N.Y.)》2005,308(5722):697-702

Agents in creative enterprises are embedded in networks that inspire, support, and evaluate their work. Here, we investigate how the mechanisms by which creative teams self-assemble determine the structure of these collaboration networks. We propose a model for the self-assembly of creative teams that has its basis in three parameters: team size, the fraction of newcomers in new productions, and the tendency of incumbents to repeat previous collaborations. The model suggests that the emergence of a large connected community of practitioners can be described as a phase transition. We find that team assembly mechanisms determine both the structure of the collaboration network and team performance for teams derived from both artistic and scientific fields.  相似文献