The importance of seasonal flow timing for riparian vegetation dynamics: a systematic review using causal criteria analysis

1. Whilst it is widely recognised that a natural flow regime is important for sustaining riverine ecosystems, the relative importance of the various components of flow regime for riparian vegetation dynamics is poorly understood. We sought to determine the current extent of knowledge on the importance of seasonal flow timing for riparian plants by conducting a systematic review of the literature using causal criteria analysis. 2. Using a definition of ‘riparian’ that included riverine, wetland and floodplain systems, we found sufficient evidence to provide strong support for the existence of causal relations between seasonal flow timing and a number of riparian plant processes, namely rates of waterborne dispersal (hydrochory), germination and growth, as well as riparian community composition. There was insufficient evidence to infer a causal relationship between flow timing and the reproduction or survival of riparian plants. 3. Thus, we argue that seasonal flow timing is important for many of the processes that generate and sustain riparian vegetation communities. River regulation, and/or flow management aimed at restoring ecological values, should consider flow timing and its implication for riparian flora. Because of regulation, many of the rivers of south‐eastern Australia have inverted seasonal flow patterns. Whilst direct evidence of the effects of this inversion on the flora of these rivers is lacking, the results of our causal analysis allow us to predict how these plant communities may have been affected. 4. However, these predictions must be treated with caution because of the reliance of some of the causal analyses on wetland studies. For riverine flora, further research is particularly needed on the effects of seasonal flow timing on hydrochory, survival and reproduction. 5. Causal criteria analysis provides a defensible and efficient means for assessing the extent of evidence for or against ecological hypotheses of this kind. In this case, systematic review of the literature provided strong evidence to support a number of causal links between seasonal flow timing and riparian vegetation dynamics, whilst also efficiently identifying knowledge gaps.     

Trophic dynamics within a hybrid zone – interactions between an abundant cyprinid hybrid and sympatric parental species

1. Recent proliferation of hybridisation in response to anthropogenic ecosystem change, coupled with increasing evidence of the importance of ancient hybridisation events in the formation of many species, has moved hybridisation to the forefront of evolutionary theory. 2. In spite of this, the mechanisms (e.g. differences in trophic ecology) by which hybrids co‐exist with parental taxa are poorly understood. A unique hybrid zone exists in Irish freshwater systems, whereby hybrid offspring off two non‐native cyprinid fishes often outnumber both parental species. 3. Using stable isotope and gut content analyses, we determined the trophic interactions between sympatric populations of roach (Rutilus rutilus), bream (Abramis brama) and their hybrid in lacustrine habitats. 4. The diet of all three groups displayed little variation across the study systems, and dietary overlap was observed between both parental species and hybrids. Hybrids displayed diet, niche breadth and trophic position that were intermediate between the two parental species while also exhibiting greater flexibility in diet across systems.     

Flow regulation affects temporal patterns of riverine plant seed dispersal: potential implications for plant recruitment

1. Changes to the natural flow regime of a river caused by flow regulation may affect waterborne seed dispersal (hydrochory), and this may be an important mechanism by which regulation affects riverine plant communities. We assessed the effect of altered timing of seasonal flow peaks on hydrochory and considered the potential implications for plant recruitment. 2. We sampled hydrochory within five lowland rivers of temperate Australia, three of which are regulated by large dams. These dams are operated to store winter and spring rains and release water in summer and autumn for agriculture. At three sites on each river, hydrochory was sampled monthly for 12 months using passive drift nets. The contents of the drift samples were determined using the seedling‐emergence method. 3. More than 33 000 seedlings from 142 taxa germinated from the samples. In general, more seeds and taxa were observed in the drift at higher flows. By altering the period of peak flows from winter–spring to summer–autumn, flow regulation similarly affected the period of peak seed dispersal. The effect of regulation on seed dispersal varied between taxa depending on their timing of seed release and whether or not they maintain a persistent soil seed bank. 4. Hydrochory in rivers is a product of flow regime and the life history of plants. By altering natural flow regimes and thus hydrochorous dispersal patterns, flow regulation is likely to affect adversely the recruitment of native plant species with dispersal phenologies adapted to natural flow regimes (such as many riparian trees and shrubs) and encourage the spread of non‐native (exotic) species. 5. Changes to hydrochorous dispersal patterns are an important mechanism by which altered flow timing affects riverine plant communities. Natural seasonal flow peaks (in this case spring) are likely to be important for the recruitment of many native riparian woody taxa.     

Interactions between growth, Cl− and Na+ uptake, and water relations of plants in saline environments. I. Slightly vacuolated cells

Abstract. Slightly vacuolated cells, i.e. microalgae and meristematic cells of vascular plants, maintain low Cl^? and Na⁺ concentrations even when exposed to a highly saline environment. The factors regulating the internal ion concentration are the relative rate of volume expansion, the membrane permeability to ions, the electrical potential, and the active ion fluxes. For ion species which are not actively transported, a formula is developed which relates the internal concentration to the rate of expansion of cell volume, the permeability of membranes to that ion, and the electrical potential. For example, when the external concentration of Cl^? is high, and Cl^? influx is probably mainly passive, the formula predicts that rapid growth keeps the internal Cl^? concentration lower than that in a non-growing cell with the same electrical potential; this effect is substantial if the plasmalemma has a low permeability to Cl^?. For ion species which are actively transported, the rate of pumping must be considered. For instance Na⁺ concentrations are kept low mainly by an efficient Na⁺ extrusion pump which works against the electric field across the membrane. The requirement for Na⁺ extrusion is related to the external Na⁺ concentration, the rate of expansion of cell volume, the membrane permeability, and the electrical potential. It is possible that microalgae have a more positive electrical potential than many other plant cells; if so, requirements for high rates of active Na⁺ extrusion will be lower. The required rates of Na⁺ extrusion are lower during rapid growth, provided that the permeability of the plasmalemma to Na⁺ is low. The energy required for the regulation of Cl^? and Na⁺ concentrations is low, especially in rapidly expanding cells where Na⁺ extrusion requires only 1–2% of the energy normally produced in respiration. The exclusion of these ions, however, must be accompanied by the synthesis of enough organic compounds to provide adequate osmotic solutes for the increases in volume accompanying growth. This process reduces the substrates available for respiration and synthesis of cell constituents, but the reduction is not prohibitively large—even for cells growing in 750 mol m^?3 NaCl, the carbohydrate accumulated as osmotic solute is only 10% of that consumed in respiration.     

Descriptive Physiology and Biochemistry of the Abnormally Ripening Tomato Fruit (Lycopersicon esculentum) cv. Snowball

Aspergillus tamarii Kita grew and sporulated best at 30°C. The best pH for growth and sporulation were 5.5 and 6.5, respectively. Among the carbon sources employed, glucose supported the highest growth and sporulation. Best growth was obtained with sodium nitrate as nitrogen source and best sporulation with ammonium tar-tarate. When glucose was used as carbon source, the carbohydrates found in the mycelium included myoinositol. dulcitol, fructose, arabinose and ribose.     

Seedling Growth Form of Oaks

Growth forms of recently-established oak seedlings were comparedamong five species from California and three species from Japan.Evergreen and deciduous species were included, native to a varietyof habitats. Each seedling was grown in a tall tube in orderto measure main root length and was harvested when leaf expansionhad ceased. The effects of light intensity reduced to 5% onseedling growth form were not strong enough to overcome theinnate differences between species. Shoot/root and leaf area/rootweight ratios were smaller in the species from drier environmentswithin each region, though all Californian oaks showed muchgreater root elongation than did the Japanese oaks. Extensiveroot systems combined with small leaf areas would help seedlingssurvival in xeric and open sites. Large leaf areas combinedwith small roots would be profitable for surviving in shadeunder canopy. In oaks of both regions, xeromorphic evergreengrowth forms are clearly distinguished from hygromorphic evergreengrowth forms. Seedling growth form, habitat moisture gradient, California oaks, Japanese oaks, shoot/root ratio     

Purification of Major Hemolymph Protein of Great Wax Moth, Galleria mellonella

Major hemolymph protein (MHP) was purified from larval hemolymph of Galleria mellonella by KBr density gradient ultracentrifugation, ion exchange chromatography (DEAE‐Trisacryl M), YM‐50 ultrafiltration and gel permeation chromatography (Sephadex G‐100). MHP is composed of two subunit (MHP‐1 and MHP‐2). The molecular weights of each subunit were determined (MHP‐1 = 86 kDa and MHP‐2 = 84 kDa). MHP is present in both hemolymph and fat body during developmental stages, indicating this protein is carrying out some functions different from other major protein such as storage protein and lipophorin.