The need for biological realism in habitat modeling: a reinterpretation of Zharikov et al. (2006)

Zharikov et al. (2006: Landscape Ecology 21:107–120) modeled the nest-site habitat use of marbled murrelets (Brachyramphus marmoratus) in Desolation Sound (DS) and Clayoquot Sound (CS), British Columbia. They compared known nest sites, located with radio-telemetry, with randomly-located points within the same areas. Their conclusions suggest that murrelets tended to nest in disproportionately smaller fragments within the more disturbed DS landscape; streams, steeper slopes, and lower elevations were selected in both landscapes; murrelets nested closer to recent clearcuts than would be expected in the DS landscape; and survivorship of nestlings was greater in areas with recent clearcuts and was positively correlated with recent habitat fragmentation. These conclusions are contrary to current management guidelines in British Columbia, and therefore require close scrutiny. Our detailed examination reveals flaws in their use of data, application of modeling, and most seriously, interpretation of the results. Problems include: conceptual errors in the interpretation of models; inappropriate spatial resolution; confusing use and interpretation of fragmentation and patch size data; overemphasis of statistically significant but biologically trivial results; and ignoring some contradictory studies. We conclude that it would be risky to apply the results from Zharikov et al. in the selection of murrelet nesting habitat for management purposes in British Columbia. Our review identifies issues that may arise in other ecological modeling studies and stresses the need for biological realism in addition to statistical rigour.     

Asynchronous Growth of the Canine Radius and Ulna: Surgical Correction following Experimental Premature Closure of the Distal Radial Physis

Marked lameness and elbow incongruity occurred in seven 21-week-old dogs following experimental premature closure of the distal radial physis at 10 weeks of age. Midradial transverse osteotomies and bone plate stabilization performed on five dogs resulted in marked reduction of elbow incongruity and forelimb lameness. Two dogs had no surgery and served as controls for the surgical procedure. At 50 weeks of age the proximal radial articular surface was displaced 5.3 mm farther from the coronoid process in control dogs as compared to dogs having transverse radial osteotomy. Markedly worse clinical, radiographic, and pathologic changes in the control group demonstrated the importance of reestablishing and preserving elbow congruity when treating asynchronous growth of the canine forelimb caused by premature closure of the distal radial physis. The technique described is recommended as one method to treat premature distal radial physeal closure clinically.     

The influence of centrifugation on quality and freezability of stallion semen

The aim of the present study was to investigate the influence of various centrifugation methods on sperm loss and quality of frozen-thawed semen. From at a total of 8 Warmblood stallions of the National Stud Farm in Avenches, 3 ejaculates each were collected and seminal plasma was removed using 3 different centrifugation regimes. In method I (reference method) centrifugation occurred by a speed of 600 x g during 10 minutes. In method II 1000 x g was used during 2 minutes while in method III centrifugation was performed by 2000 x g during 2 minutes. After centrifugation 90%, of the supernatant was removed and sperm loss calculated. After resuspension of the pellet with freezing medium, functional membrane integrity was evaluated by HOS-test and motility determined. In frozen-thawed semen motility, viability as well as functional membrane integrity (HOS-test) and acrosome status using chlortetracyclinassay (CTA) were assessed. Our results demonstrate that mean sperm loss (I, 1.9%; II, 8.7%; III, 3.7%) was significantly (P < 0.05) different between the three centrifugation regimes. Regarding semen quality of frozen-thawed semen, HOS in method III (52.1%) was significantly lower than in methods I (55.5%) and II (55.3%). Evaluation of the acrosome status by CTA showed that more than 70% of sperm cells were capacitated and 25% capacitated and acrosome reacted. From our results we conclude that sperm loss and functional membrane integrity (HOS-test) in frozen-thawed semen were significantly influenced by the centrifugation regime. Therefore, stallion semen should be centrifuged at 600 x g during 10 minutes before freezing in order to obtain low sperm loss and a good quality of frozen-thawed semen.     

Maintenance energy requirements and the effect of diet on performance of racing Greyhounds

OBJECTIVES: To determine maintenance energy requirements and effect of diet on performance of racing Greyhounds. ANIMALS: 7 adult racing Greyhounds. PROCEDURE: Dogs were fed a higher fat and protein (HFP) or a lower fat and protein (LFP) diet for 8 weeks in a crossover design. Dogs were exercised for 15 minutes twice daily in a paddock and raced 500 m twice weekly. Blood gas, hematologic, and serum biochemical analyses were performed before and after racing, and race times were compared at the end of each diet period. RESULTS: Mean race time was significantly shorter (32.81+/-0.65 seconds vs. 33.05+/-0.71 seconds), and mean racing speed over 500 m was significantly faster (15.25+/-0.30 vs. 15.13+/-0.30 m x s(-1)) when dogs were fed the HFP diet than when they were fed the LFP diet. Diet had little or no effect on results of blood gas, hematologic, and serum biochemical analyses, except that Hct was 4% greater before and after racing when the HFP diet was fed than when the LFP diet was fed. Mean SD metabolizable energy intake from weeks 1 through 16 was 155+/-9 kcal x kg(-0.75) x d(-1). CONCLUSIONS AND CLINICAL RELEVANCE: Racing Greyhounds ran faster when fed a diet containing higher fat and protein and lower carbohydrate contents. Their maintenance metabolizable energy requirement was slightly higher than that of moderately active dogs.     

Inheritance of equine sarcoid disease in Franches-Montagnes horses

The mode of inheritance for susceptibility to equine sarcoid disease (ES) remains unknown. The objectives of this study were to analyse a large sample of the Franches-Montagnes (FM) horse population and investigate the heritability and mode of inheritance for susceptibility to ES. Horses were clinically examined for the presence of sarcoid tumours. A standardized examination protocol and client questionnaire were used and a pedigree- and subsequent segregation-analysis for the ES trait performed. To investigate the mode of inheritance, five models were evaluated and compared in a hierarchical way.The analyses reveal that variation in susceptibility to ES is best explained by a model incorporating polygenic variation. The possible effect of a major gene, such as specific equine leukocyte antigen alleles, is unlikely, but cannot be ruled-out entirely. The heritability of the phenotype on the observation scale for the trait ‘affected with ES’ was estimated to be 8%. A corrected value for the heritability on a liability scale was estimated at 21% and it is therefore possible to estimate breeding values for ES. The arguments against the practical implementation of an estimated breeding value in a multifactorial condition like ES are discussed.     

Genetic differentiation of indigenous (Quercus robur L.) and late flushing oak stands (Q. robur L. subsp. slavonica (Gáyer) Mátyás) in western Germany (North Rhine-Westphalia)

European Journal of Forest Research - Slavonian oaks (Quercus robur subsp. slavonica (Gáyer) Mátyás) originating from Croatia have been cultivated in Germany mainly in the...     

Distribution of grapevine leafroll associated virus-3 variants in South African vineyards

Three genetic variants of Grapevine leafroll-associated virus 3 (GLRaV-3) were identified from vineyards of the Western Cape, South Africa. In a previous study, three full genome sequences of isolates representing each of the variant groups were determined. The three variant groups were represented by accessions 621, 623 and PL-20, of variant groups I, II and III respectively. A specific single strand conformation polymorphism (SSCP) profile was assigned to each variant which was used as a quick, reliable detection and differentiation method. In this study we analysed the occurrence of these three GLRaV-3 variants in mother blocks in different cultivars and from different vine growing regions using SSCP. The majority of the plants studied, were infected with the group II variant, similar to isolates 623 and GP18. The distribution of three GLRaV-3 variants within a spatio-temporally recorded cluster of diseased plants was studied by means of SSCP profile analysis of ORF5 amplified PCR products. We showed that different GLRaV-3 variants are transmitted to adjacent plants in an infection cluster. Results showed that, in some leafroll disease clusters, the variant that was present in the original GLRaV-3 infected plant of a cluster was transmitted to adjacent plants in a row and across rows.     

Avian utilisation on six salt marshes in New Jersey

Bird use was measured on six salt marshes in New Jersey from 18 April to 18 July 1977 (2 impoundments, 2 ditched marshes and 2 natural salt marshes) in terms of species diversity, numbers of individuals and biomass. Seventy-eight species of birds were recorded in all six marshes although not all species occurred on each marsh. Species diversity was highest on the impoundments, intermediate on the ditched marshes, and lowest in the natural marshes. Species diversity and the number of individuals directly related to the amount of open surface area. The traditional species typical of salt marshes on the East Coast of North America (clapper rails Rallus longirostris, seaside and sharp-tailed sparrows Ammospiza spp.) occurred primarily in the natural salt marshes and were absent from the impoundments. Considerations of species diversity suggest that diversity in salt marsh types is essential to maintaining high species diversity in salt marsh ecosystems. Red-winged blackbirds Agelaius phoeniceus and swallows were the most numerous species, followed by gulls and terns. The impoundments had over five times as many individuals as the natural marshes. Waterfowl, gulls, terns and waders accounted for over 90% of the cumulative biomass in the six marshes, with waterfowl contributing over 50%. This study suggests that conservationists should encourage the maintenance of natural salt marshes because they are necessary habitats for some species even though the diversity and avian biomass is less on natural salt marsh areas than it is on managed areas.