Environmental change and the phenology of European aphids

Aphids, because of their short generation time and low developmental threshold temperatures, are an insect group expected to respond particularly strongly to environmental changes. Forty years of standardized, daily data on the abundance of flying aphids have been brought together from countries throughout Europe, through the EU Thematic Network 'EXAMINE'. Relationships between phenology, represented by date of first appearance in a year in a suction trap, of 29 aphid species and environmental data have been quantified using the residual maximum likelihood (REML) methodology. These relationships have been used with climate change scenario data to suggest plausible changes in aphid phenology. In general, the date of first record of aphid species in suction traps is expected to advance, the rate of advance varying with location and species, but averaging 8 days over the next 50 years. Strong relationships between aphid phenology and environmental variables have been found for many species, but they are notably weaker in species living all year on trees. Canonical variate analysis and principal coordinate analysis were used to determine ordinations of the 29 species on the basis of the presence/absence of explanatory variables in the REML models. There was strong discrimination between species with different life cycle strategies and between species feeding on herbs and trees, suggesting the possible value of trait-based groupings in predicting responses to environmental changes.     

Two new species of Multiclavula (lichenized basidiomycetes) from savanna soils in Rwanda (East Africa)

Two new species of Multiclavula are described from Rwanda: M. akagerae , with a thallus consisting of turgescent glomerules, and M. rugaramae , with a thallus composed of flattened, rounded, marginate, and dispersed squamules. They grow on soil in frequently burned savannas or on lateritic soils in eastern Rwanda. The genus Lepidostroma should probably be reduced into synonymy with Multiclavula .  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 457–465.     

The tobacco Ntann12 gene, encoding an annexin, is induced upon Rhodoccocus fascians infection and during leafy gall development

Annexins are calcium-binding proteins that have been associated in plants with different biological processes such as responses to abiotic stress and early nodulation stages. Until now, the implication of annexins during plant–pathogen interactions has not been reported. Here, a novel plant annexin gene induced in tobacco BY-2 cell suspension cultures infected with the phytopathogenic bacterium Rhodococcus fascians (strain D188) has been identified . Expression of this gene, called Ntann12 , is also induced, but to a lower extent, by a strain (D188-5) that is unable to induce leafy gall formation. This gene was also induced in BY-2 cells infected with Pseudomonas syringae but not in cells infected with Agrobacterium tumefaciens or Escherichia coli. Ntann12 expression was also found to be stimulated by abiotic stress, including NaCl and abscissic acid, confirming a putative role in stress signal transduction pathways. In addition, promoter- GUS analyses using homozygous transgenic tobacco seedlings showed that the developmentally controlled expression of Ntann12 is altered upon R. fascians infection. Finally, up-regulation of Ntann12 during leafy gall ontogenesis was confirmed by RT-qPCR. Discussion is focused on the potential role of Ntann12 in biotic and abiotic stress responses and in plant development, both processes that may involve Ca²⁺-dependent signalling.     

Membrane water permeability and aquaporin expression increase during growth of maize suspension cultured cells

Aquaporins (AQPs) are water channels that allow cells to rapidly alter their membrane water permeability. A convenient model for studying AQP expression and activity regulation is Black Mexican Sweet (BMS) maize cultured cells. In an attempt to correlate membrane osmotic water permeability coefficient (P_f) with AQP gene expression, we first examined the expression pattern of 33 AQP genes using macro-array hybridization. We detected the expression of 18 different isoforms representing the four AQP subfamilies, i.e. eight plasma membrane (PIP), five tonoplast (TIP), three small basic (SIP) and two NOD26-like (NIP) AQPs. While the expression of most of these genes was constant throughout all growth phases, mRNA levels of ZmPIP1;3 , ZmPIP2;1 , ZmPIP2;2, ZmPIP2;4 and ZmPIP2;6 increased significantly during the logarithmic growth phase and the beginning of the stationary phase. The use of specific anti-ZmPIP antisera showed that the protein expression pattern correlated well with mRNA levels. Cell pressure probe and protoplast swelling measurements were then performed to determine the P_f. Interestingly, we found that the P_f were significantly increased at the end of the logarithmic growth phase and during the steady-state phase compared to the lag phase, demonstrating a positive correlation between AQP abundance in the plasma membrane and the cell P_f.     

Experimental herbivory of native Australian macrophytes by the introduced Mozambique tilapia Oreochromis mossambicus

This study describes experimental herbivory and detritivory of three common native aquatic macrophyte species by the introduced Mozambique tilapia Oreochromis mossambicus (Peters) (Pisces: Cichlidae), and its physiological response to their consumption. There was a highly significant effect of fish herbivory on plant weight for each of the macrophyte species, but this effect was not influenced by any preference for periphyton. Despite the herbivory, there was a highly significant loss of fish body weight across all plant species and weight could only be maintained by supplementary feeding of a high protein fish flake. These results suggest that despite eating these plants, an alternative food resource may be needed for survival and may trigger trophic plasticity in O. mossambicus.     

Antisense inhibition of the sucrose transporter in potato: effects on amount and activity

The sucrose proton-cotransporter gene from potato (StSUT1) is mainly expressed in the phloem of mature, exporting leaves. To study the in vivo role of the protein, potato plants were transformed with antisense constructs of the sucrose transporter cDNA under control of the CaMV35S and the rolC promoters, respectively. Both types of transgenic plant develop symptoms characteristic of an inhibition of phloem loading. To determine the level of inhibition, immunological and transport studies were performed. Purified antibodies directed against a peptide from the central loop of SUT1 recognized a transporter with an apparent molecular mass of 47 kDa in leaf plasma membrane vesicles. Antisense repression under control of the non-specific CaMV35S promoter led to a strong reduction in SUT1 protein, whereas no such reduction could be detected when the companion cell-specific rolC promoter was used. Similarily. sucrose uptake in plasma membrane vesicles was reduced by 50–75% in CaMV35S but not in rolC plants. These data suggest that, unlike the rolC promoter, the sucrose transporter is expressed not only in the companion cells but also in other leaf cells. However, inhibition of the transporter by rolC-controlled antisense repression is sufficient to impair phloem loading.     

Modelling the impacts of flow regulation on fish distributions in naturally intermittent lowland streams: an approach for predicting restoration responses

1. Understanding the relationships between flow regime and the distribution of biota is critical for managing flows in regulated rivers. In northern Victoria, Australia, efforts are presently underway to restore a natural, intermittent flow regime to several streams which, for over 100 years, have received perennial diversions as part of a stock, irrigation and domestic water supply. 2. Bayesian, model‐averaged, binomial regression was used to predict probabilities of occurrence for 13 fish species, including five non‐native species, based on hydrologic variables characterising both the current and modelled future flow regimes at 10 sites representing a range of hydrologic regimes (categorised here as heavily regulated, moderately regulated and unregulated). 3. Regression models accurately predicted present probabilities of occurrence for most species across all sites. The models predicted a reduced likelihood of large, native, flow‐dependent species occurring at regulated sites following flow restoration. Predictions regarding the future distribution of widespread species including two small‐bodied native and four exotic species were less certain as current distributions of these widespread species were unrelated to hydrologic variables we examined and thus unlikely to be significantly affected by flow restoration. The distributions of two small native species currently restricted to unregulated sites are predicted to increase throughout the system. 4. This study illustrates the effects of artificially induced perennial flow on lowland fish distributions. Furthermore, the combination of pre‐restoration data together with predictive modelling provides valuable insights into the likely outcomes of flow regime shifts. 5. This study clearly demonstrates the value of combining empirical research and modelling in guiding environmental flow and ecosystem restoration decisions. Knowledge from the study is now helping guide management decisions and the development of mitigation strategies to protect highly valued species in the system from potential future threats.     

Classifying the fire‐response traits of plants: How reliable are species‐level classifications?

Plant species in fire‐prone environments possess specific traits which allow them to survive fire. Species are commonly classified according to whether they survive fire and resprout or whether they are killed by fire and regenerate from seed. However, different populations of the same species have been shown to vary in their responses. Therefore, the classification of a species into a single category based on fire‐response traits may not necessarily be representative of every population under every circumstance. This study examined the extent of within‐species variation in fire‐response traits of woody plants in south‐eastern Australia after the 2003 fires. Species were then classified using two approaches: (i) using data from a field survey of fire‐response traits, taking into account within‐species variation; and (ii) using species' fire responses listed in a pre‐existing fire‐response database compiled from a variety of primary sources. Field data showed that the majority of species in the study area resprouted after fire with around one in 10 species variable in their resprouting response. Almost half of all species varied from site to site according to whether they regenerated from seed, either solely or in addition to resprouting. The numbers of species classified as resprouters and seed regenerators varied according to the classification method used. Differences were also found between the classification method when calculating the mean proportion of resprouters and seed regenerators across sites. The fire‐response traits for some species from the database were found to differ from the observed field responses. This study demonstrated that the application of a fire‐response trait, reported in a trait database, to an entire species, may not adequately represent the actual fire responses of the populations of interest. Rather than considering the fire‐response traits of a species, accurate prediction may be better achieved by considering how different populations of plants will respond to fire.