Does sample length influence the shape of xylem embolism vulnerability curves? A test with the Cavitron spinning technique

The Cavitron spinning technique is used to construct xylem embolism vulnerability curves (VCs), but its reliability has been questioned for species with long vessels. This technique generates two types of VC: sigmoid ‘s’‐shaped and exponential, levelling‐off ‘r’‐shaped curves. We tested the hypothesis that ‘r’‐shaped VCs were anomalous and caused by the presence of vessels cut open during sample preparation. A Cavitron apparatus was used to construct VCs from samples of different lengths in species with contrasting vessel lengths. The results were compared with VCs obtained using other independent techniques. When vessel length exceeded sample length, VCs were ‘r’‐shaped and anomalous. Filling vessels cut open at both ends with air before measurement produced more typical ‘s’‐shaped VCs. We also found that exposing segments of 11 woody species in a Cavitron at the pressure measured in planta before sampling considerably increased the degree of embolism above the native state level for species with long vessels. We concluded that open vessels were abnormally more vulnerable to cavitation than intact vessels. We recommend restricting this technique to species with short conduits. The relevance of our conclusions for other spinning techniques is discussed.     

Spatial and temporal dynamics of rabies virus variants in big brown bat populations across Canada: footprints of an emerging zoonosis

Phylogenetic analysis of a collection of rabies viruses that currently circulate in Canadian big brown bats (Eptesicus fuscus) identified five distinct lineages which have emerged from a common ancestor that existed over 400 years ago. Four of these lineages are regionally restricted in their range while the fifth lineage, comprising two‐thirds of all specimens, has emerged in recent times and exhibits a recent demographic expansion with rapid spread across the Canadian range of its host. Four of these viral lineages are shown to circulate in the US. To explore the role of the big brown bat host in dissemination of these viral variants, the population structure of this species was explored using both mitochondrial DNA and nuclear microsatellite markers. These data suggest the existence of three subpopulations distributed in British Columbia, mid‐western Canada (Alberta and Saskatchewan) and eastern Canada (Quebec and Ontario), respectively. We suggest that these three bat subpopulations may differ by their level of female phylopatry, which in turn affects the spread of rabies viruses. We discuss how this bat population structure has affected the historical spread of rabies virus variants across the country and the potential impact of these events on public health concerns regarding rabies.     

Text messaging: an innovative method of data collection in medical research

Background

The ubiquitous use of mobile phones in sending and receiving text messages has become a norm for young people. Undeniably, text messaging has become a new and important communication medium not only in the social realm but in education as well. The aim of this study is to evaluate the effectiveness of using text messaging as a means to collect data for a medical research project.A cross sectional study was carried out during a double blind, randomized controlled trial to assess the efficacy and safety of a probiotic in the management of Irritable Bowel Syndrome (IBS). The study aim was to assess the response rate of weekly symptom reports via Short Message Service (SMS). The subjects were undergraduates in a private medical university in Malaysia. They were identified through a previous university wide study as suffering from IBS based on Rome III criteria. The subjects were randomly assigned to either the treatment arm receiving a daily probiotic, or the placebo arm. They were required to score their symptoms using eight-item-questionnaires at baseline, and thereafter weekly, for a total of 8 weeks. All subjects were given the choice to communicate their symptom scores by text messaging via mobile phones or by email. SMS text messages were sent to remind trial subjects to attend face-to-face visits and to complete a paper based 34-item-questionnaires on IBS quality of life assessment at baseline and at end of 8 weeks.

Findings

The response rate of weekly symptom scores via Short Message Service (SMS) from a total of 38 subjects was 100%. Through the study, 342 reports were submitted: 33.3% of these were received on the due date without reminder, 60.0% one day after the deadline, after a single reminder, 6.1% 2-3 days after the deadline, after 2-3 reminders and 0.6% 5 days after the deadline, after SMS, phone reminder and face-to-face encounter. All SMS symptom reports, whether on time or late, were complete. With the help of SMS reminder, all trial subjects completed the paper based IBS quality of life assessment at baseline and at end of study.

Conclusions

This study found using text messaging via mobile phone an excellent instrument for collecting weekly symptom reports in response to trial medication, reminding trial subjects to attend face to face visits and completing more complex paper based evaluation. The 100% response rate of weekly symptom reports was facilitated by using simple number codes for SMS submission.

Trial Registration

Not appropriate.

     

Characterization of microsatellite loci isolated in trumpeter swan (Cygnus buccinator)

Primers for 16 microsatellite loci were developed for the trumpeter swan (Cygnus buccinator), a species recovering from a recent population bottleneck. In a screen of 158 individuals, the 16 loci were found to have levels of variability ranging from two to seven alleles. No loci were found to be linked, although two loci repeatedly revealed significant departures from Hardy–Weinberg equilibrium. Amplification in the closely related tundra swan (Cygnus columbianus) was successful for all except one locus. These microsatellite loci will be applicable for population genetic analyses and ultimately aid in management efforts.     

Endophytic fungi decrease available resources for the aphid Rhopalosiphum padi and impair their ability to induce defences against predators

Abstract.  1. The production of winged morphs is a well known mechanism of induced defence in aphids to escape from natural enemies, and is also a reaction to poor resource quality.
2. Host plants of aphids often associate with endophytic fungi that have been shown to reduce the fitness of some species of aphids.
3. It was hypothesised that endophyte infection of host plants that represent a low quality plant resource should increase the aphid's induced response to a predator because both low plant quality and predator presence represent a stronger cue for wing production than predator presence alone.
4. In a laboratory experiment, bird cherry-oat aphids Rhopalosiphum padi L. were exposed to the factors predator threat and endophyte infection and the effects of these factors on the proportion of winged morphs produced by the aphid colonies was analysed.
5. The presence of endophytic fungi strongly decreased aphid colony sizes. When a predator threat was present, all colonies on endophyte-free grasses produced winged morphs whereas only a few colonies were able to produce winged morphs on endophyte-infected grasses. However, these few colonies produced larger proportions of winged morphs than colonies on endophyte-free grasses. Without a predator threat, no colonies on endophyte-infected grasses produced any winged morphs.
6. These results show that aphids in stressed conditions and with reduced fitness will only invest in inducible defences when predators are present but are unable to produce winged morphs in response to endophyte presence.     

Polyploid evolution and plastid DNA variation in the Dactylorhiza incarnata/maculata complex (Orchidaceae) in Scandinavia

The Dactylorhiza incarnata/maculata complex (Orchidaceae) was used as a model system to understand genetic differentiation processes in a naturally occurring polyploid complex with much of ongoing diversification and wide distribution in recently glaciated areas in northern Europe. Data were obtained for 12 hypervariable regions in the plastid DNA genome. A total of 166 haplotypes were found in a sample of 1099 plants. Allopolyploid taxa have inherited their plastid genomes from D. maculata s.l. Overall haplotype diversity of the combined group of allopolyploid taxa was comparable to that of maternal D. maculata s.l., but populations of allopolyploids were also more strongly differentiated from each other and contained lower numbers of haplotypes than populations of D. maculata s.l. In addition to haplotypes found in extant D. maculata s.l., the allopolyploids also contained several distinct and widespread haplotypes that were not found in any of the parental lineages. Some of these haplotypes were shared between widespread allopolyploids. Divergent allopolyploids with small distributions did not seem to originate from local polyploidization events, but rather as segregates of already existing allopolyploids. Genetic diversification of allopolyploid Dactylorhiza is the result of repeated polyploid formation, secondary hybridization and introgression between already existing polyploids and extant representatives of parental lineages, hybridization between independently derived polyploid lineages, and phyletic diversification in the group of allopolyploids. Although some polyploid taxa must have evolved after the last glaciation, genetic material from the parental lineages has been transferred continuously for longer periods of time. This combination of processes may explain the taxonomic complexity encountered in Dactylorhiza and other polyploid complexes distributed in previously glaciated parts of Europe.