The effects on Arbutus unedo L. of long-term exposure to elevated CO2

Arbutus unedo is a sclerophyllous evergreen, characteristic of Mediterranean coastal scrub vegetation. In Italy, trees of A. unedo have been found close to natural CO₂ vents where the mean atmospheric carbon dioxide concentration is about 2200 μmol mol^?1. Comparisons were made between trees growing in elevated and ambient CO₂ concentrations to test for evidence of adaptation to long-term exposure to elevated CO₂. Leaves formed at elevated CO₂ have a lower stomatal density and stomatal index and higher specific leaf area than those formed at ambient CO₂, but there was no change in carbon to nitrogen ratios of the leaf tissue. Stomatal conductance was lower at elevated CO₂ during rapid growth in the spring. In mid-summer, under drought stress, stomatal closure of all leaves occurred and in the autumn, when stress was relieved, the conductance of leaves at both elevated and ambient CO₂ increased. In the spring, the stomatal conductance of the new flush of leaves at ambient CO₂ was higher than the leaves at elevated CO₂, increasing instantaneous water use efficiency at elevated CO₂. Chlorophyll fluorescence measurements suggested that elevated CO₂ provided some protection against photoinhibition in mid-summer. Analysis of A/C_i curves showed that there was no evidence of either upward or downward regulation of photosynthesis at elevated CO₂. It is therefore anticipated that A. unedo will have higher growth rates as the ambient CO₂ concentrations increase.     

The Effect of Oxygen on Endogenous Cytokinin Levels and Germination of Leucadendron daphnoides Seed

The soybean callus assay was used to study the effect of high oxygen tensions on the cytokinin levels of Leucadendron daphnoides Meisn. seed, where dormancy is apparently due to the restricting effect of the seed coat on oxygen diffusion to the embryo. High oxygen tensions led to a six-fold increase in germination compared to seed incubated in air and resulted in significant increases in butanol soluble cytokinins prior to visible germination. It is suggested that the primary effect of oxygen is to increase the rate of respiration and thus, to provide the energy required for the synthesis of butanol soluble cytokinins which leads to cotyledon expansion and subsequent radicle elongation. Present indications are that untreated seeds remain dormant due to low concentrations of butanol soluble cytokinins in their embryos.     

Impacts of climate on prey abundance account for fluctuations in a population of a northern wader at the southern edge of its range

Understanding the mechanisms by which climate change will affect animal populations is vital for adaptive management. Many studies have described changes in the timing of biological events, which can produce phenological mismatch. Direct effects on prey abundance might also be important, but have rarely been studied. We examine the likely importance of variation in prey abundance in driving the demographics of a European golden plover ( Pluvialis apricaria ) population at its southern range margin. Previous studies have correlated plover productivity with the abundance of their adult cranefly (Tipulidae) prey, and modelled the phenology of both plover breeding and cranefly emergence in relation to temperature. Our analyses demonstrate that abundance of adult craneflies is correlated with August temperature in the previous year. Correspondingly, changes in the golden plover population are negatively correlated with August temperature 2 years earlier. Predictions of annual productivity, based on temperature-mediated reductions in prey abundance, closely match observed trends. Modelled variation in annual productivity for a future scenario of increasing August temperatures predicts a significant risk of extinction of the golden plover population over the next 100 years, depending upon the magnitude of warming. Direct effects of climate warming upon cranefly populations may therefore cause northward range contractions of golden plovers, as predicted by climate envelope modelling. Craneflies are an important food source for many northern and upland birds, and our results are likely to have wide relevance to these other species. Research into the potential for habitat management to improve the resilience of cranefly populations to high temperature should be an urgent priority.     

The bee‐killing flies,genus Melaloncha Brues (Diptera: Phoridae): a combined molecular and morphological phylogeny

The phylogeny of the bee‐killing flies, genus Melaloncha Brues (Diptera: Phoridae) is analysed using six genes –cytochrome oxidase I, 16S ribosomal DNA, 12S ribosomal DNA, NADH1 dehydrogenase, 28S ribosomal DNA and CAD– plus 47 morphological characters. A total of 91 specimens, including eight out‐groups and 83 Melaloncha (representing 70 species) were included in the analyses. Parsimony analysis of the combined data set produced a single most parsimonious tree with varied Bremer and bootstrap support of interior nodes. Bayesian analysis of molecules only and of morphology + molecules produced trees largely in agreement with parsimony results, although with a few differences. Supported groups included subfamily Metopininae, genus Melaloncha, and subgenera Melaloncha s.s. and Melaloncha (Udamochiras) Enderlein. Within the subgenera, the previously recognized Melaloncha furcata, Melaloncha cingulata, Melaloncha ungulata and Melaloncha stylata groups were recovered, as well as some new groupings. The M. furcata group was placed as the sister group of other Melaloncha s.s., which is consistent with known host‐attacking behaviour.     

Rapid expansion of the cane toad (Bufo marinus) invasion front in tropical Australia

Abstract Cane toads (Bufo marinus) are large toxic anurans that have spread through much of tropical Australia since their introduction in 1935. Our surveys of the location of the toad invasion front in 2001 to 2005, and radiotracking of toads at the front near Darwin in 2005, reveal much faster westwards expansion than was recorded in earlier stages of toad invasion through Queensland. Since reaching the wet‐dry tropics of the Northern Territory, the toads have progressed an average of approximately 55 km year⁻¹ (mean rate of advance 264 m night⁻¹ along a frequently monitored 55‐km road transect during the wet season of 2004–2005). Radiotracking suggests that this displacement is due to rapid locomotion by free‐ranging toads rather than human‐assisted dispersal; individual toads frequently moved >200 m in a single night. One radiotracked toad moved >21 800 m in a 30‐day period; the fastest rate of movement yet recorded for any anuran. Daily displacements of radiotracked toads varied with time and local weather conditions, and were highest early in the wet season on warm, wet and windy nights. The accelerated rate of expansion of the front may reflect either, or both: (i) evolved changes in toads or (ii) that toads have now entered an environment more favourable to spread. This accelerated rate of expansion means that toads will reach the Western Australian border and their maximal range in northern Australia sooner than previously predicted.