The Effects of Compatible Solutes on the Heat Stability of Glutamine Synthetase from Chickpeas Grown under Different Nitrogen and Temperature Regimes

The activity of glutamine synthetase (GS) extracted from chickpeasgrown under different nitrogen and temperature regimes was examined.Cytosolic GS (GS₁) was much less temperature sensitive thanchloroplastic GS (GS₂). There was no change in the ratio ofthe two isoforms from plants with different growth temperatures.Specific activity of GS appeared to be independent of growthtemperature and was little affected by nitrogen supply. In vitro studies were performed on the heat stability of GS₂in the presence of glycine betaine, proline, and myoinositol.The latter was most effective in preventing loss of enzyme activityat high temperatures. Glycine betaine was also effective asa heat protectant but enzyme activity in the presence of prolinewas lower than the control at temperatures above 30 ?C. Theimportance of myo-inositol protection of metabolism is discussedin relation to the accumulation in chickpeas of another cyclitol,pinitol. Key words: Chickpeas, high temperature stress, glutamine synthetase     

Effects of nitrogen supply and high temperature on the growth and physiology of the chickpea

Chickpeas were grown with or without nitrate nitrogen feeding, or nodulated with Rhizobium leguminosarum. High [40°C day, 25°C night (HT)] and moderate [25°C day, 177°C night (LT)] temperature regimes were employed during growth. Growth rates, photosynthetic capacity and enzymes of carbon and nitrogen metabolism were monitored to assess the acclimatory capacity of the chickpea. Initial growth rates were stimulated by high temperatures, particularly in nitrate-fed and nodulated plants. Older HT plants had fewer laterals, smaller leaves, and fewer flowers were produced than in LT plants. There was some indication of an acclimation of photosynthesis to high temperatures and this was independent of nitrogen supply. Rubisco activity was increased by high growth temperatures. However, HT plants also had higher transpiration rates and lower water use efficiency than LT plants both in respective growth conditions and when compared in a common condition. High temperatures reduced shoot nitrate reductase activity but had little effect on root activity, which was the same if not greater than activity in LT roots. The amino acid, asparagine, was found at high concentrations in all treatments. Concentrations were maintained throughout growth in HT plants but declined with age in LT plants.     

Experimental transplants of mice (Pseudomys and Mus) on to early stages of post-mining regeneration in open forest

Results are presented for three controlled replicated experiments in which mice were transplanted onto the early successional stages of two regenerating mining paths. Naive house mice (Mus musculus) were successfully introduced on to sites regenerating for 8 years, with 56% remaining after 3 days and 2% still present after 69 days. Naive New Holland mice (Pseudomys novaehollandiae) had marginal establishment success on sites regenerating for 4.9 years, with 21% remaining after 3 days and 3% still present after 22 days. However, on sites regenerating for 3.9 years and 4.4 years, all 17 transplanted New Holland mice had dispersed from the treatment plots after 3 days. New Holland mice have been shown to be competitively dominant to house mice. Hence, we conclude that the reason New Holland mice do not colonize mining paths regenerating for less than 4.9 years is the unsuitability of the habitat rather than their exclusion by house mice. These results are consistent with the early stages of the mammalian succession following sand mining and fit the same habitat accommodation model proposed for post-fire mammalian succession.     

Asymmetric impacts of two herbivore ecotypes on similar host plants

1. Ecotypes may arise following allopatric separation from source populations. The simultaneous transfer of an exotic plant to a novel environment, along with its stenophagous herbivore, may complicate more traditional patterns of divergence from the plant and insect source populations. 2. The present study evaluated herbivory effects by two Cyrtobagous salviniae ecotypes on two species of Salvinia: the larger S. molesta and the smaller S. minima. Evaluations were based on relative growth rates, biomass production, coverage, and nutrient cycling in a series of complementary and comparative laboratory and outdoor tank experiments. 3. In general, the experiment results indicated that the smaller Florida ecotype of C. salviniae impacted both Salvinia species more than the larger Brazil ecotype. Herbivory, especially by the Florida ecotype, also improved water quality and accelerated nutrient cycling by increasing the rates of litterfall from the standing crops of salvinia. 4. The smaller size of the Florida ecotype may be adaptive by allowing maximal exploitation of host plants via internal larval feeding, which presumably reduces predation risk while increasing damage to the plant. These findings provide support for relying on the suppressive effects of the Florida ecotype in Florida, rather than introducing the Brazil ecotype to counter new infestations of S. molesta.     

Climate change at the landscape scale: predicting fine-grained spatial heterogeneity in warming and potential refugia for vegetation

Current predictions of how species will respond to climate change are based on coarse‐grained climate surfaces or idealized scenarios of uniform warming. These predictions may erroneously estimate the risk of extinction because they neglect to consider spatially heterogenous warming at the landscape scale or identify refugia where species can persist despite unfavourable regional climate. To address this issue, we investigated the heterogeneity in warming that has occurred in a 10 km × 10 km area from 1972 to 2007. We developed estimates by combining long‐term daily observations from a limited number of weather stations with a more spatially comprehensive dataset (40 sites) obtained during 2005–2006. We found that the spatial distribution of warming was greater inland, at lower elevations, away from streams, and at sites exposed to the northwest (NW). These differences corresponded with changes in weather patterns, such as an increasing frequency of hot, dry NW winds. As plant species were biased in the topographic and geographic locations they occupied, these differences meant that some species experienced more warming than others, and are at greater risk from climate change. This species bias could not be detected at coarser scales. The uneven seasonal nature of warming (e.g. more warming in winter, minimums increased more than maximums) means that climate change predictions will vary according to which predictors are selected in species distribution models. Models based on a limited set of predictors will produce erroneous predictions when the correct limiting factor is not selected, and this is difficult to avoid when temperature predictors are correlated because they are produced using elevation‐sensitive interpolations. The results reinforce the importance of downscaling coarse‐grained (∼50 km) temperature surfaces, and suggest that the accuracy of this process could be improved by considering regional weather patterns (wind speed, direction, humidity) and topographic exposure to key wind directions.     

Snake diets and the deep history hypothesis

The structure of animal communities has long been of interest to ecologists. Two different hypotheses have been proposed to explain origins of ecological differences among species within present‐day communities. The competition–predation hypothesis states that species interactions drive the evolution of divergence in resource use and niche characteristics. This hypothesis predicts that ecological traits of coexisting species are independent of phylogeny and result from relatively recent species interactions. The deep history hypothesis suggests that divergences deep in the evolutionary history of organisms resulted in niche preferences that are maintained, for the most part, in species represented in present‐day assemblages. Consequently, ecological traits of coexisting species can be predicted based on phylogeny regardless of the community in which individual species presently reside. In the present study, we test the deep history hypothesis along one niche axis, diet, using snakes as our model clade of organisms. Almost 70% of the variation in snake diets is associated with seven major divergences in snake evolutionary history. We discuss these results in the light of relevant morphological, behavioural, and ecological correlates of dietary shifts in snakes. We also discuss the implications of our results with respect to the deep history hypothesis. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 476–486.     

Transport and settlement of organic matter in small streams

1. After it enters streams, terrestrially derived organic matter (OM) rapidly absorbs water. Using field and laboratory experiments, we examined how this process affected the buoyancy, settling velocity, transport distance and retention locations of four types of organic matter typically found in Pacific coastal streams (‘flexible’ red alder leaves and three ‘stiff’ particle types – Douglas‐fir needles, red cedar fronds and Douglas‐fir branch pieces). 2. Immersion in water rapidly changed the physical characteristics of alder leaves, Douglas‐fir needles and red cedar fronds, which all reached constant still‐water settling velocities after only a few days of soaking. In contrast, the settling velocity of branch pieces continued to increase for 13 days, eventually reaching much higher values than any other OM type. Dried alder leaves became negatively buoyant after only two days of immersion, while other types took substantially longer (up to 24 days) before the specific gravity of all particles was >1. 3. We released saturated OM particles in an experimental channel and found that all particle types travelled further in a fast, shallow ‘riffle’ than a slow, deep ‘pool’. Comparisons with a passive settlement null model indicated that leaves were retained more rapidly than expected in the riffle (by large protruding stones), while the three stiff particle types travelled further than expected (probably due to turbulent suspension) and were retained when they settled in deeper water between larger stones. In pools, passive settlement appeared to dominate the retention of all OM types, with leaves travelling furthest. 4. These retention patterns corresponded well with those observed when saturated OM particles collected in the field were released in two pools and two riffles in a second‐order coastal stream. 5. When the experimental channel and in‐stream data were combined, the retention rates of the three stiff OM types were closely related to calculated Rouse numbers (Rouse number = particle settling velocity/shear velocity), whereas the retention rate of alder leaves was not. This suggests that different physical mechanisms are responsible for the retention of leaves and stiff OM types in shallow streams.     

Survival and Cause-Specific Mortality of Neonatal Mule Deer Fawns,North-Central New Mexico

Abstract: Because of significant declines in mule deer (Odocoileus hemionus) populations across New Mexico, USA, we investigated survival of fawns in north-central New Mexico, USA. We captured 19 fawns, 34 fawns, and 47 fawns in 2002, 2003, and 2004, respectively, and used fawn morphological measurements, habitat characteristics, and adult female (hereafter “female”) condition to model preweaning fawn survival. Survival was 0.0, 0.12, 0.52 for 2002, 2003, and 2004, respectively, and was related to birth mass (χ₁² = 9.5, P = 0.002), birth date (χ₁²= 8.4, P = 0.004), litter size (χ₂² = 9.4, P = 0.009), female body fat (χ₁² = 40.9, P < 0.001), annual precipitation (χ₁² = 35.0, P < 0.001), summer precipitation (χ₁²= 37.5, P < 0.001), and winter precipitation (χ₁² = 32.0, P < 0.001). Total ingesta-free body fat of females (β = 3.01, SE = 0.75; odds ratio = 20.19, 95% CI = 4.64-87.91) and birth mass of fawns (β = 1.188, SE = 0.428; odds ratio = 3.38, 95% CI = 1.42-7.59) were the best predictors of survival of individual fawns, although few of the logistic models differed in model selection criteria. Fawn survival in north-central New Mexico was driven by an interaction of total and seasonal precipitation and its effect on plant production, consequential effects on female nutrition, and ultimately, fawn birth attributes. Habitat conditions were so poor throughout north-central New Mexico during 2002 and 2003 (and likely during other drought yr) that, based upon birth attributes, few fawns could have survived regardless of proximate causes of mortality. In 2004, precipitation enhanced security cover, maternal body condition, birth attributes and, thus, survival of fawns. However, more habitat enhancements are needed to improve the nutritional quality of mule deer habitats in north-central New Mexico and further enhance maternal and fawn condition to recover mule deer populations in this region.     

The effects of buried magnets on colonies of Amitermes spp. building magnetic mounds in northern Australia1

ABSTRACT Unlike four control colonies of Amitermes which built normal, north-south oriented 'magnetic' mounds in northern Australia, four young colonies failed after exposure to experimental alteration of the earth's magnetic field. In November 1979, bar magnets were buried on either side at the base of each of three new nests of Amitermes laurensis Mjoberg and one new colony of A.vitiosus Hill. As controls, non-magnetized iron bars were disposed similarly in relation to three new nests of the former species and one of the latter. In September 1986, all four control nests had grown normally. However, not one of the treatment colonies survived and from what remained of the former nest in each case it is clear that the demise of the colonies occurred soon after the magnets were placed. We conclude that the failure of these colonies was the result of the changed magnetic environment. Whether 'magnetic' termites use magnetoperception as a cue to achieve their spectacular north-south orientation remains unknown, but the results of this field experiment weigh more for than against this possibility.