Evolution and development of inflorescence architectures

To understand the constraints on biological diversity, we analyzed how selection and development interact to control the evolution of inflorescences, the branching structures that bear flowers. We show that a single developmental model accounts for the restricted range of inflorescence types observed in nature and that this model is supported by molecular genetic studies. The model predicts associations between inflorescence architecture, climate, and life history, which we validated empirically. Paths, or evolutionary wormholes, link different architectures in a multidimensional fitness space, but the rate of evolution along these paths is constrained by genetic and environmental factors, which explains why some evolutionary transitions are rare between closely related plant taxa.     

Tissue tropism of African horsesickness virus in the chicken embryo demonstrated with the avidin-biotin complex immunoperoxidase method

In horses, African horsesickness virus (AHSV) exhibits marked tropism for certain microvascular endothelia and components of the mononuclear phagocyte system. In this study, the tropism of a field isolate of AHSV serotype 5 was studied in 24 chicken embryos. Histopathology on embryonic tissues harvested with 12 hour intervals revealed progressive changes associated with endothelial damage. Immunolabeling demonstrated viral antigens in the microvascular endothelium of the spleen, lungs, and the mesenchymal connective tissue at the base of the neck, from 24 hours post inoculation. Subsequently, specific immunolabeling increased steadily in endothelia of these and other tissues such as skeletal and cardiac muscle, gastrointestinal smooth muscle, mesonephric glomeruli, liver, subcutis and feathers. Positive immunolabeling was also occasionally observed in circulating mononuclear cells and in Kupffer cells in the liver. It was concluded, that this isolate of AHSV displayed similar tissue tropism in the chicken embryo as in the horse.     

Efficacy and acceptability of the new oral phosphate binder Lenziaren® in healthy cats fed a renal diet

The efficacy and acceptability of the new oral phosphate binder Lenziaren^® (SBR759) were evaluated in healthy cats fed with a commercial diet containing low amounts of phosphate (‘renal diet’). Lenziaren^® at 0.125, 0.25, 0.5 and 1 g/day was compared to a reference product Lantharenol^® (3.0 g/day) and a placebo in a masked, randomized, parallel‐group design study in 36 cats (n = 6 per group). All products were mixed with the ration which was fed once daily for 28 days. Lenziaren^® produced significant dose‐related reductions in serum and urine phosphate concentrations, faecal apparent phosphorus digestibility and fractional urinary phosphate excretion. Cats administered Lenziaren^® consumed significantly less food than the placebo group, but this had no negative impact on body weight or acceptability assessments. When compared to the positive control, Lantharenol^®, Lenziaren^® was significantly more acceptable (0.125, 0.5 and 1.0 g/day doses), was associated with higher food consumption (0.125, 0.5 and 1.0 g/day doses) and had greater efficacy in reducing serum phosphate (0.5 and 1.0 g/day) and urine phosphate concentrations (1.0 g/day). In conclusion, Lenziaren^® was an effective oral phosphate binder in healthy cats fed with a renal diet. Lenziaren^® was well accepted and tolerated. Dosages of 0.25–1.0 g/cat per day are recommended for clinical testing.     

Nutrient cycling and greenhouse gas emissions from soil amended with biochar-manure mixtures

Integrating biochar into cattle diets has recently emerged as a potential management practice for improving on-farm productivity.Yet,information concerning the cycling of biochar-manure mixtures is scarce.A 70-d incubation experiment was conducted within two surface(0–15 cm)Mollisols with contrasting textures,i.e.,sandy clay loam(Raymond)and clayey(Lethbridge),to evaluate the effects of biochar(3 Mg ha^-1)on cumulative greenhouse gas(GHG)emissions and related fertility attributes in the presence or absence of cattle manure(120 Mg ha^-1).Five treatments were included:i)non-amended soil(control,CK),ii)soil amended with pinewood biochar(B),iii)soil amended with beef cattle manure(M)(manure from cattle on a control diet),iv)soil amended with biochar-manure(BM)(manure from cattle on a control diet,with pinewood biochar added at 20 g kg^-1of diet dry matter),and v)soil amended with B and M at the aforementioned rates(B+M).A total of 40 soil columns were prepared and incubated at 21℃and 60%–80%water-holding capacity.On average,total CO₂fluxes increased by 2.2-and 3.8-fold under manure treatments(i.e.,M,BM,and B+M),within Raymond and Lethbridge soils,respectively,relative to CK and B.Similarly,total CH4 fluxes were the highest(P<0.05)in Raymond soil under B+M and BM relative to CK and B,and in Lethbridge soil under M and BM relative to CK and B.In Lethbridge soil,application of BM increased cumulative N₂O emissions by 1.8-fold relative to CK.After 70-d incubation,amendment with BM increased(P<0.05)PO_4-P and NO_3-N+NH_4-N availability in Raymond and Lethbridge soils compared with B.A similar pattern was observed for water-extractable organic carbon in both soils,with BM augmenting(P<0.05)the occurrence of labile carbon over CK and B.It can be concluded that biochar,manure,and/or biochar-manure have contrasting short-term effects on the biogeochemistry of Mollisols.At relatively low application rates,biochar does not necessarily counterbalance manure-derived inputs.Although BM did not mitigate the flux of GHGs over M,biochar-manure has the potential to recycle soil nutrients in semiarid drylands.     

Compatibility of the ammonium lactate (AL) and sodium bicarbonate (Olsen) methods for determining available phosphorus in Swedish soils

Abstract

Plant-available P was first extracted in soils 114 years ago and a number of different analytical methods have since been developed, but for good reasons none of these methods has been adopted as a standard for all soils. With increasing cooperation within research, there is a need to harmonise the interpretation of analytical data for fertiliser recommendations, research, and environmental control. This paper evaluates the compatibility of the Swedish standard ammonium lactate (P_AL) method and the widely used Olson's sodium bicarbonate (P_Ols) method in 82 topsoil samples taken from Swedish long-term soil fertility field trials. The P_AL-values were usually larger than P_Ols, with a mean P_AL/P_Ols quotient of 2.30±1.04 (0.67–6.58). The P_AL and P_Ols means and ranges were 126±89 (5–360) and 55.1±33 (3.1–122.8) mg P kg^?1 dry soil, respectively. Stepwise multiple linear regression analysis was used to evaluate the relationship between P_AL and P_Ols and how this relationship was affected by clay content, pH, and soil organic carbon content (SOC). After statistical transformation, it emerged that the square root of clay content (17.4%±13.82, range 1–54.4) and pH (6.45±0.54, range 5.5–7.7) significantly affected the relationship at partial R ²-values of 2 and 12%, respectively, while ln(SOC) (2.54%±1.21, range 1–6.03) did not, apparently due the narrow range. The regressions of predicted vs. measured values explained 95 and 94% of the variation in P_AL and P_Ols, respectively. The mean deviation of predicted compared with measured values was 21.3 and 8.3 mg P kg^?1 dry soil for P_AL and P_Ols, respectively, corresponding to 20 or 19% of the measured values. We conclude that a data set consisting of P_AL-values can be converted into P_Ols-values and vice versa with reasonably high accuracy when accounting for clay content and pH.     

Gut and intestinal passage time in the Rainbow Skink (Trachylepis margaritifer): implications for stress measures using faecal analysis

Stress levels in organisms provide a rapid measure for assessing population health. Handling and capture stress, however, cause error in blood measures, so this method is rapidly being replaced by assessing levels of stress metabolites in faeces. This eliminates the source of error because there is a lag period between stress perception and the resultant stress metabolite accumulation within faeces. This lag period is correlated with specific intestinal passage time, a measure that can vary greatly between taxa, particularly amongst ectotherms. Due to two deleterious consequences associated with extended exposure of the metabolites to the intestinal environment, species that exhibit long and variable intestinal passage times are not good candidates for metabolite studies. We measured gut and intestinal passage times in Trachylepis margaritifer to ascertain whether it would be an appropriate candidate for stress metabolite studies. We first tested if barium sulphate in the meal had an effect on gut passage time at three ambient temperatures (25, 27 and 32 °C). Barium sulphate had no effect; however, temperature had a significant effect with an unexpected pattern: gut passage time was fastest at 32 °C but was slower at 27 °C than at 25 °C. We then used X‐ray technology and barium sulphate‐loaded meals to measure gut and intestinal passage times at 25 and 27 °C. This allowed us to observe which parts of the digestive process were responsible for increased passage times at 27 °C: the faster passage time at 25 °C was due to faster intestinal passage time; there was no difference in gastric emptying time. We assess the species to be a suitable candidate for studies using faeces to measure stress. It is imperative however, that the effect of temperature on passage rates is known and taken into account in such studies.     

Determinations of the reproductive output of populations of a thalassinid prawn Upogebia africana (Ortmann) in the Swartkops estuary

Populations of large and ‘stunted’ (adult carapace lengths = 17,0–24,0 and 12,0–19,0 mm respectively) Upogebia africana were regularly and quantitatively sampled in the Swartkops estuary. At the site with ‘stunted’ prawns a well-defined spring (July to October) and summer (December to March) breeding cycle was recorded. The ‘stunted’ female prawns produced two broods of eggs per annum and the brood size ranged from about 305 to 2282 eggs depending on the size of the female. At the site with large prawns the spring and summer breeding cycles tended to merge, forming a longer breeding season, with the adult females apparently producing three broods of eggs per annum. The brood size of these females ranged from about 1304 to 4819 eggs. The calculated reproductive output (Pr) and reproductive biomass ratio (Pr/B) of the latter population were much greater than those of the ‘stunted’ prawns (1331 kJ m^?2 y^? and 0,53 v. 332 kJ m^?2 y^?1 and 0,26).     

Methods to detect species range size change from biological atlas data: A comparison using the South African Frog Atlas Project

Comparing historical species distribution data with recent biological surveys has the potential to quantify changes to species geographic ranges, and to detect declining species. The primary concern in making species range size comparisons between dissimilar datasets is the problem of incomparable sampling intensities. For South African amphibian data, an increase in sampling intensity over time was associated with a move from ad hoc to more coordinated sampling. The consequent increased geographic coverage and higher detection probabilities resulted in false range expansions. We assessed several approaches for managing variable sampling intensity: categorical comparisons, sub-sampling and correction factors. These methods were first applied to hypothetical ranges for evaluation, and then to the observed data of the South African Frog Atlas Project. Categorical comparisons oversimplified quantitative data and correctly measured the sign of change for fewer than 56% of the hypothetical ranges. Sub-sampling methods correctly estimated the sign of change for up to 78% of the hypothetical ranges, but it is essential to balance data removal with a reduction of false range expansions. The best measure of hypothetical range change was a mathematical correction factor, which achieved 83% accuracy in detecting the correct sign of change and 50% for the magnitude of change. According to this method, 68 (60.2%) South African frog species are likely to have undergone range contractions. The careful use of methods such as those assessed here allows for ad hoc data collections and biological surveys to be valuable in quantifying species range change, and hence for identifying potentially declining species.