Variability of invertebrate herbivory on the submerged macrophyte Potamogeton perfoliatus

1. Invertebrate herbivory was studied in twenty-eight populations of the submerged macrophyte Potamogeton perfoliatus in Danish streams and lakes in mid-June. All populations but one experienced invertebrate herbivory and loss ranged from 0 to 11.9% of leaf area among populations. Loss generally increased with leaf age towards the base of the plants, and young apical leaves were rarely damaged. 2. Herbivory loss was significantly higher in streams (mean 5.0%) than in lakes (mean 2.2%), but varied greatly among populations within the same stream or lake and was not correlated to physico-chemical site characteristics, size or density of plant population, or leaf N and P content. High levels of invertebrate herbivory were therefore not associated with certain types of streams or lakes. 3. High herbivore biomass relative to abundance of plants was conducive to high loss. In streams, the biomass of the trichopteran Anabolia nervosa accounted for 50% of the variability in loss. No single species appeared to be equally important in lakes, although loss was correlated to the biomass of the chrysomelid beetle Macroplea appendiculata. Obligate herbivores, such as lepidopteran larvae, apparently exerted little damage on P. perfoliatus, and leaf mining and channelization from specialist feeders were negligible. It is concluded that shredders acting as facultative herbivores were the most important invertebrate herbivores on P. perfoliatus in Danish freshwaters.     

THE INFLUENCE OF BAT DETECTOR BRAND ON THE QUANTITATIVE ESTIMATION OF BAT ACTIVITY

ABSTRACT

Bat detectors are commonly used to monitor bat behaviour. Earlier research has suggested that there may be systematic differences in the response of different detectors to bat calls. Such differences would have important implications for the comparability of quantitative surveys conducted with bat detectors. The present study examines variability within and between brands of bat detector in accuracy of tuning, directionality and sensitivity to different types of bat echolocation call in bat detectors from three manufacturers. The consistency of results from a field survey incorporating the three brands in a standardised methodology are also examined. Significant differences were found within and between brands in directionality and sensitivity which would lead to bias in bat surveys. The implications of these findings for bat surveys are discussed, as are the design features of importance for species identification.     

A role for oxalic acid generation in ozone‐induced signallization in Arabidopis cells

Ozone (O₃) is an air pollutant with an impact increasingly important in our industrialized world. It affects human health and productivity in various crops. We provide the evidences that treatment of Arabidopsis thaliana with O₃ results in ascorbate‐derived oxalic acid production. Using cultured cells of A. thaliana as a model, here we further showed that oxalic acid induces activation of anion channels that trigger depolarization of the cell, increase in cytosolic Ca²⁺ concentration, generation of reactive oxygen species and cell death. We confirmed that O₃ reacts with ascorbate in the culture, thus resulting in production of oxalic acid and this could be part of the O₃‐induced signalling pathways that trigger programmed cell death.     

Preliminary estimates of the potential for carbon mitigation in European soils through no-till farming

In this paper we estimate the European potential for carbon mitigation of no-till farming using results from European tillage experiments. Our calculations suggest some potential in terms of (a) reduced agricultural fossil fuel emissions, and (b) increased soil carbon sequestration. We estimate that 100% conversion to no-till farming would be likely to sequester about 23 Tg C y^–1 in the European Union or about 43 Tg C y^–1 in the wider Europe (excluding the former Soviet Union). In addition, up to 3.2 Tg C y^–1 could be saved in agricultural fossil fuel emissions. Compared to estimates of the potential for carbon sequestration of other carbon mitigation options, no-till agriculture shows nearly twice the potential of scenarios whereby soils are amended with organic materials. Our calculations suggest that 100% conversion to no-till agriculture in Europe could mitigate all fossil fuel-carbon emissions from agriculture in Europe. However, this is equivalent to only about 4.1% of total anthropogenic CO₂-carbon produced annually in Europe (excluding the former Soviet Union) which in turn is equivalent to about 0.8% of global annual anthropogenic CO₂-carbon emissions.     

Effects of fine‐scale genetic structure on male mating success in gynodioecious Beta vulgaris ssp. maritima

Plant mating systems are known to influence population genetic structure because pollen and seed dispersal are often spatially restricted. However, the reciprocal outcomes of population structure on the dynamics of polymorphic mating systems have received little attention. In gynodioecious sea beet (Beta vulgaris ssp. maritima), three sexual types co‐occur: females carrying a cytoplasmic male sterility (CMS) gene, hermaphrodites carrying a non‐CMS cytoplasm and restored hermaphrodites that carry CMS genes and nuclear restorer alleles. This study investigated the effects of fine‐scale genetic structure on male reproductive success of the two hermaphroditic forms. Our study population was strongly structured and characterized by contrasting local sex‐ratios. Pollen flow was constrained over short distances and depended on local plant density. Interestingly, restored hermaphrodites sired significantly more seedlings than non‐CMS hermaphrodites, despite the previous observation that the former produce pollen of lower quality than the latter. This result was explained by the higher frequency of females in the local vicinity of restored (CMS) hermaphrodites as compared to non‐CMS hermaphrodites. Population structure thus strongly influences individual fitness and may locally counteract the expected effects of selection, suggesting that understanding fine scale population processes is central to predicting the evolution of gender polymorphism in angiosperms.     

What makes an ophiuroid? A morphological study of the problematic Ordovician stelleroid Stenaster and the palaeobiology of the earliest asteroids and ophiuroids

Extant asteroids and ophiuroids [EchinodermataJ are distinguished by differences in arm support, water vascular system structures and in details of arm and jaw structure. However, some lower Palaeozoic taxa show combinations of both asteroid-like and ophiuroid-like characters and their morphology and functional biology is poorly understood. This paper redescribes one such taxon, the middle-upper Ordovician stellate echinoderm Stenaster and clarifies its phylogenetic status. Characters in common with extant and Ordovician ophiuroids, include arm support due primarily to ambulacral ossicles, presence of extensive longitudinal arm musculature, a mobile jaw and an internalised radial water vessel with internalised podial pores. In addition, Stenaster lacks several characters which are conventionally considered to be asteroid-like, for example an axillary, madreporitc, marginal ossicles and a true ambulacral groove. However, in overall shape Stenaster is remarkably asteroid-like, showing short, broad-based arms shared podial basins and a small disc. A cladistic analysis of early asteroids, ophiuroids and somasteroid taxa consistently places Stenaster within the ophiuroids and suggests secondary convergence to asteroids. In functional terms, Stenaster is interpreted as an ophiuroid which has secondarily adopted a semi-infaunal, deposit-feeding mode of life, analogous to that of some extant paxillosid asteroids.     

Molecular cloning and expression profiles of calreticulin gene from the diamondback moth,Plutella xylostella

Calreticulin (CRT) plays pivotal roles in Ca²⁺ homeostasis, molecular chaperoning, infection, inflammation and innate immunity. In an attempt to study the involvement of CRT in innate immunity, the full-length cDNA of calreticulin (PxCRT) was cloned from the diamondback moth, Plutella xylostella. It consists of 1674 bp (excluding poly-A tail) with a longest open reading frame (ORF) of 1197 bp encoding 398 amino acids. In silico analysis of PxCRT ORF reveals that it has various repeat motifs and endoplasmic reticulum retention signal found in all the calreticulin proteins. As expected, high amino acid sequence identities were found from other CRTs identified from Bombyx mori (87%), Galleria mellonella (87%), Apis mellifera (74%), Anopheles gambiae (74%), Tribolium castaneum (73%), Culex quinquefasciatus (73%), Rhodnius prolixus (72%), Nasonia vitripennis (71%), Drosophila melanogaster (71%) and Haemaphysalis qinghaiensis (68%). During development, P. xylostella expressed PxCRT predominantly in the pupal stage. In addition, spatial expression pattern analysis indicates that PxCRT was highly expressed in the silk gland. PxCRT mRNA, furthermore, was strongly induced 3 to 6 h after laminarin treatment, suggesting that PxCRT appears to be involved in immune responses and also plays an important role in the silk gland.