Altitudinal distribution limits of aquatic macroinvertebrates: an experimental test in a tropical alpine stream

1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle. 2. This was experimentally addressed using aquatic macroinvertebrates; larvae of Andesiops (Ephemeroptera), Claudioperla, (Plecoptera), Scirtes (Coleoptera) and Anomalocosmoecus (Trichoptera), and the amphipod Hyalella in an Ecuadorian glacier‐fed stream (4100–4500 m a.s.l.). The following were performed: (i) quantitative benthic sampling at three sites to determine altitudinal patterns in population densities, (ii) transplants of the five taxa upstream of their natural altitudinal limit to test the short‐term (14 days) effect on survival, and (iii) in situ experiments of locomotory activity as a proxy for animal response to relatively small differences in temperature (5 °C vs. 10 °C) and oxygen saturation (55% vs. 62%). 3. The transplant experiment reduced survival to a varying degree among taxa, but Claudioperla survived well at a site where it did not naturally occur. In the in situ experiment, Scirtes and Hyalella decreased their activity at lower oxygen saturation, whereas Andesiops and Anomalocosmoecus did so at a low temperature. The decrease in activity from a high to a low temperature and oxygen for the five taxa was significantly correlated with their mortality in the transplant experiment. 4. Together the present experiments indicate that even relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits.     

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.     

Two New Kalyptorhynchia (Turbellaria) from the Coast of Northern New England,USA1

Cystiplana rubra sp.n. and Crassicollum musculare gen. et sp.n. are described and their taxonomy discussed. C. rubra (family Cystiplanidae Karling, 1964) is distinguished by red pigmented stripes, two pairs of cuticular pieces within the copulatory bulb, a small male atrium posterior to the copulatory bulb, and a two part atrial bulb. C. musculare is characterized by a large, unpaired prostatic vesicle with two distinct regions of secretory products, a muscular penis papilla with a small apical stylet, large muscle bolsters bracketing a glandular evagination of the genital atrium, and a large sphincter encircling the genital canal. A new family of Eukalyptorhynchia, Crassicollidae, is erected. Notes on some biological aspects of these species are included.     

SEM study of surface structures of the spathe in Cryptocoryne and Lagenandra (Araceae: Aroideae: Cryptocoryneae)

SEM studies of the spathe structures in the two closely related genera Cryptocoryne and Lagenandra show differences between the inner and outer surfaces, as well as in cell structures in the various parts of the spathe. The cell structure reveals patterns mat makes it possible to depict homologous structures of the spathe, even though the spathes of the two genera look different. The basal part of the kettle has a mucilage covering of the cells, interpreted as a hitherto unnoticed food source. The cells of the inner surface of the kettle and tube have downward pointing trichomes. On the second day of flowering these collapse and sink into the cell lumen, which is suggested to create a unique lattice-like structure that enables the insects to climb out of the kettle and tube. The cell structure of the flap shows that it is a prolongation and continuation of the spathe tube margin.     

Isolation of fungal DNA from plant tissues and removal of DNA amplification inhibitors

Specific primers and the polymerase chain reaction (PCR) are increasingly used for detection of fungi in plants. Detection depends on isolation of DNA that is free of compounds that inhibit amplification. We report on the significance of inhibition in soybean stems with a focus on studies of the vascular fungal pathogen Phialophora gregata. A simple DNA extraction procedure based on a FastDNA® kit is described that allows consistent detection of fungi in soybean stems using PCR. The addition of polyvinylpyrrolidone and supplemental DNA purification steps overcame inhibition in over 90% of samples. These methods should also facilitate studies with other plant and fungal species.     

Agroinfection-based high-throughput screening reveals specific recognition of INF elicitins in Solanum

We adapted and optimized the use of the Agrobacterium tumefaciens binary PVX expression system (PVX agroinfection) to screen Solanum plants for response to pathogen elicitors and applied the assay to identify a total of 11 clones of Solanum huancabambense and Solanum microdontum , out of 31 species tested, that respond to the elicitins INF1, INF2A and INF2B of Phytophthora infestans . Prior to this study, response to INF elicitins was only known in Nicotiana spp. within the Solanaceae. The identified S. huancabambense and S. microdontum clones also exhibited hypersensitivity-like cell death following infiltration with purified recombinant INF1, INF2A and INF2B, thereby validating the screening protocol. Comparison of INF elicitin activity revealed that Nicotiana plants responded to significantly lower concentrations than Solanum , suggesting variable levels of sensitivity to INF elicitins. We exploited natural variation in response to INF elicitins in the identified Solanum accessions to evaluate the relationship between INF recognition and late blight resistance. Interestingly, several INF-responsive Solanum plants were susceptible to P. infestans . Also, an S. microdontum  × Solanum tuberosum (potato) population that segregates for INF response was generated but failed to identify a measurable contribution of INF response to resistance. These results suggest that in Solanum , INF elicitins are recognized as general elicitors and do not have a measurable contribution to disease resistance.     

Excising stem samples underwater at native tension does not induce xylem cavitation

Xylem resistance to water stress‐induced cavitation is an important trait that is associated with drought tolerance of plants. The level of xylem cavitation experienced by a plant is often assessed as the percentage loss in conductivity (PLC) at different water potentials. Such measurements are constructed with samples that are excised underwater at native tensions. However, a recent study concluded that cutting conduits under significant tension induced cavitation, even when samples were held underwater during cutting. This resulted in artificially increased PLC because of what we have termed a ‘tension‐cutting artefact’. We tested the hypothesized tension‐cutting artefact on five species by measuring PLC at native tension compared with after xylem tensions had been relaxed. Our results did not support the tension‐cutting artefact hypothesis, as no differences were observed between native and relaxed samples in four of five species. In a fifth species (Laurus nobilis), differences between native and relaxed samples appear to be due to vessel refilling rather than a tension‐cutting effect. We avoided the tension‐cutting artefact by cutting samples to slightly longer than their measurement length and subsequent trimming of at least 0.5 cm of sample ends prior to measurement.     

Two temperature-sensitive photosystem II mutants of pea

Two nuclear gene mutants of pea, chlorotica-887 and chlorina-5756, are temperature-sensitive in the development of photosystem II activity. Low temperature flourescence emission spectra of leaves show that the peak at 697 nm from the reaction center of photosystem II is present when the mutants have been grown at 18°C, but absent when they have been grown at 30°C. For leaves of chlorina-5756 grown at 18°C the relative size of the peak at 697 nm is reduced compared to that of leaves of the wild type or chlorotica-887 grown at this temperature. Flourescence induction curves of leaves from wild type plants and chlorotica-887 grown at 18°C possess two steps, while those of leaves from chlorina-5756 grown at 18°C or 30°C and chlorotica-887 grown at 30°C show at fast rise to the maximal level of fluorescence. Measurements on chloroplasts isolated from the mutants indicated that the photosystem I activity per g leaf material is comparable for plants grown at 18°C and plants grown at 30°C. In contrast, no photosystem II activity was detected when the mutants had been grown at 30°C. It is suggested that these mutants are affected in a component required for the assembly of functional photosystem II complexes.