Vascular plant changes in extreme environments: effects of multiple drivers

The Antarctic Peninsula is one of three regions of the planet that have experienced the highest rates of climate warming over recent decades. Based on a comprehensive large-scale resurvey, allowing comparison of new (2009) and historical data (1960s), we show that the two native Antarctic vascular plant species have exhibited significant increases in number of occupied sites and percent cover since the 1960s: Deschampsia antarctica increasing in coverage by 191 % and in number of sites by 104 %. Colobanthus quitensis increasing in coverage by 208 % and number of sites by 35 %. These changes likely occurred in response to increases of 1.2 °C in summer air temperature over the same time period. Both species exhibited changes with elevation due to the interaction of multiple drivers (climatic factors and animal disturbance), producing heterogeneity of responses across an elevation gradient. Below an elevation of 20 m fur seal activity exerted negative impacts. Between 20 and 60 m, both plant species underwent considerable increases in the number of sites and percent cover, likely influenced by both climate warming and nutrient input from seals. Above an elevation threshold of 60 m the maximum elevation of the sites occupied decreased for both species, perhaps as a consequence of physical disturbance at higher elevations due to the permafrost conditions and/or the snow cover thickness and persistence. Understanding the role of disturbance drivers for vegetation change in cold regions may become a research priority to enable improved forecasting of biological responses and feedbacks of climate warming on ecosystems in these globally influential regions

The role of dehydration and ice nucleators in the survival of polar arthropods

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN024580 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Water relations during desiccation of cysts of the potato-cyst nematode Globodera rostochiensis

The loss during desiccation of osmotically active water (OAW), which freezes during cooling to -45 °C, and osmotically inactive water (OIW), which remains unfrozen, from the cysts of the potato cyst nematode, Globodera rostochiensis, was determined using differential scanning calorimetry. Exotherms and endotherms associated with non-egg compartments were not detected after 5 min desiccation at 50% relative humidity and 20 °C. The pattern of water loss from the cysts indicates that water is lost from compartments outside the eggs first, that nearly all the non-egg water is OAW and that the OIW content of the cyst is contained within the eggs. Water is lost from the eggs only after the OAW content outside the eggs falls below that within the eggs. Both OAW and OIW are lost from the eggs during desiccation but the eggs retain a small amount of OIW. Other animals which survive some desiccation but which are not anhydrobiotic will tolerate the loss of OAW but not the loss of their OIW. Anhydrobiotic animals can survive the loss of both their OAW and a substantial proportion of their OIW

First report of an entomophthoralean fungus on an arthropod host in Antarctica

A species of the fungus Neozygites (Zygomycetes: Entomophthorales) is recorded from the Antarctic mite Alaskozetes antarcticus (Acarina: Oribatidales) collected off the west coast of the Antarctic peninsula. The features of the fungus were similar to those recorded for Neozygites acaridis, and to other species of the genus recorded from mites in tropical and cool-temperate regions. This is the first report of any entomophthoralean fungus from the Antarctic region

Are the Antarctic dipteran, Eretmoptera murphyi, and Arctic collembolan, Megaphorura arctica, vulnerable to rising temperatures?

Polar terrestrial invertebrates are suggested as being vulnerable to temperature change relative to lower latitude species, and hence possibly also to climate warming. Previous studies have shown Antarctic and Arctic Collembola and Acari to possess good heat tolerance and survive temperature exposures above 30 °C. To test this feature further, the heat tolerance and physiological plasticity of heat stress were explored in the Arctic collembolan, Megaphorura arctica, from Svalbard and the Antarctic midge, Eretmoptera murphyi, from Signy Island. The data obtained demonstrate considerable heat tolerance in both species, with upper lethal temperatures ≥35 °C (1 h exposures), and tolerance of exposure to 10 and 15 °C exceeding 56 days. This tolerance is far beyond that required in their current environment. Average microhabitat temperatures in August 2011 ranged between 5.1 and 8.1 °C, and rarely rose above 10 °C, in Ny-Ålesund, Svalbard. Summer soil microhabitat temperatures on Signy Island have previously been shown to range between 0 and 10 °C. There was also evidence to suggest that E. murphyi can recover from high-temperature exposure and that M. arctica is capable of rapid heat hardening. M. arctica and E. murphyi therefore have the physiological capacity to tolerate current environmental conditions, as well as future warming. If the features they express are characteristically more general, such polar terrestrial invertebrates will likely fare well under climate warming scenario

Chromosomal location of genes encoding for resistance to septoria tritici blotch (Mycosphaerella graminicola) in substitution lines of wheat

Chromosomal location of resistance to Mycosphaerella graminicola was studied in substitution lines of resistant Triticum genotypes into the (susceptible) cultivar Chinese Spring (T. aestivum). (Moderately) resistant genotypes for which substitution lines were available were tested in a first screening. We selected a synthetic hexaploid wheat (Synthetic 6x; T. dicoccoides x T. tauschii), T. spelta and the wheat (T. aestivum) cultivars Cheyenne and Cappelle-Desprez. In a second screening the most suitable Argentinian isolates were identified. We decided to use the isolate IPO 92067 (all sets of substitution lines), IPO 93014 (substitution lines of Synthetic 6x, Cappelle-Desprez and T. spelta) and IPO 92064 (substitution lines of Cheyenne). In the final experiments, substitution lines of the selected genotypes into Chinese Spring were grown in two different environments and inoculated with the selected isolates at the seedling stage (lines of all four selected genotypes) or the adult stage (lines of Synthetic 6x and Cheyenne). Resistance was expressed as (reduction in) necrosis percentage or pycnidial coverage percentage; the two measures were highly (linearly) correlated. When tested in the seedling stage, all chromosomes seemed to carry genes effective against M. graminicola. Many genes were effective against only one isolate or in only one environment or their effects only showed in one resistance parameter. Often these effects were minor. Only chromosome 7D of Synthetic 6x was found with a major effect against both isolates tested. When tested in the adult stage, all lines but the one carrying chromosome 4B from the resistant parent seemed to show genes effective against M. graminicola. The line carrying chromosome 7D from Synthetic 6x showed a level of resistance similar to the resistant parent for isolate IPO 92067, but not for isolate IPO 93014. Major genes, effective against both isolates, were also found on chromosomes 5A and 5D from Synthetic 6x. Lines carrying chromosome 1B, 5D or 6D from Cheyenne showed major effects against isolate IPO 92064. For both necrosis percentage and pycnidial coverage percentage, highly significant linear correlations were found between resistance in the seedling stage and resistance in the adult stage. However, the variance accounted for was only small (20¿24%; n = 184)

Comparative thermal tolerance of herbivorous and predatory beetles on South Georgia, Sub-Antarctic

On the sub-Antarctic island of South Georgia the field distributions of two herbivorous perimyloid beetles Hydromedion sparsutum and Perimylops antarcticus overlap with the latter occurring at higher altitudes. An introduced predatory carabid beetle (Trechisibus antarcticus) is found in the coastal lowlands in close association with H. sparsutum. Laboratory experiments confirmed the hypothesis that the distribution and origin of the species is relected in a decreasing order of cold hardiness (P. antarcticus > H. sparsutum > T. antarcticus) with the sequence reversed in exposures at high temparatures. The use of such laboratory assessments (supercooling points, upper and lower lethal temperatures) when applied to single species and as a comparative bioassay, is discussed

Raman spectroscopic studies of Antarctic endoliths and epiliths

Antarctica has long been recognised as a putative analogue for Mars' past (1) and any life there is surviving in extreme conditions. Raman spectroscopy has been proved as a suitable method of analysis of lichens, (2) as it does not destroy the sample, can be used in situ and does not require any sample preparation. In this report the progression of life from extreme to very extreme conditions has been investigated. Cyanobacterial mats live on the surface in areas where water is available. As water becomes less available epilithic lichens become the main life form, and as conditions get more extreme the lichens grow as chasmoliths and endoliths

Influence of plant height and heading date on the expression of the resistance to Septoria tritici blotch in near isogenic lines of wheat

The effects of plant height and heading date on the expression of the resistance to Septoria tritici blotch, which is caused by the fungus Mycosphaerella graminicola (Fuckel) Schroeter, in Cohn (Septoria tritici Rob. ex Desm.), were investigated in wheat (Triticum aestivum L.) near isogenic lines in the Mercia and Cappelle-Desprez background and differing in dwarfing genes (Rht) or in genes for insensitivity to photoperiod (Ppd). The experimental design was a randomized block design with four replications conducted over 2 yr. Necrosis percentage at boot (growth stage GS 49), milk (GS 73), and dough stage (GS 85); area under disease progress curve (AUDPC); plant height; and heading date were recorded. The shortest lines, Mercia Rht12, Mercia Rht3, and Cappelle-Desprez Rht3, showed higher necrosis percentage and AUDPC values than their respective controls. Mercia lines with Ppd1 and Cappelle-Desprez Ppd1 and Ppd2, the earliest heading lines, showed lower necrosis values than their respective controls. Multiple regression models including plant height and heading date accounted for 44.3 to 99.1% of the variation in necrosis percentage and were statistically significant in most cases. Reduced plant height was usually associated with more necrosis because of the highest necrosis percentage of the shortest lines. Late heading date was not associated or positively associated with more necrosis because of favorable weather conditions for late heading cultivars. When weather variables were included in the models, several of them replaced days to heading, suggesting that the positive relationship between necrosis and days to heading was caused by environmental conditions. Corrections of disease severity values for heading date and plant height should be done in breeding programs when selecting for resistance