Effects of varying character definitions on classification of Genisteae (Leguminosae)

Six different sets of morphological taxonomic data were recorded for 175 species of the tribe Genisteae; these were based on the same observations, but four data sets differed in the definition of character states and three data sets differed in the method of selecting characters. Linkage diagrams drawn from single-link clustering results were markedly different for each data set and might have led taxonomists to propose quite different classifications. The arrangements in five of the six results agreed closely in parts with one or more of the four published systems for the tribe. It is concluded that the characterization of interspecific variation in the Genisteae into comparative characters is an unstable process, and that this process may be unstable in other instances.     

An Evaluation of Commercial Thiosulphate Citrate Bile Salt Sucrose Agar (TCBS)

The recovery of vibrios, in particular Vibrio cholerae , non-cholera vibrios and V. parahaemolyticus , on four brands of TCBS has been compared. The selectivity of the media was also compared. Eiken TCBS performed best in our tests but was closely followed by Oxoid TCBS.     

Climate change and plant regeneration from seed

At the core of plant regeneration, temperature and water supply are critical drivers for seed dormancy (initiation, break) and germination. Hence, global climate change is altering these environmental cues and will preclude, delay, or enhance regeneration from seeds, as already documented in some cases. Along with compromised seedling emergence and vigour, shifts in germination phenology will influence population dynamics, and thus, species composition and diversity of communities. Altered seed maturation (including consequences for dispersal) and seed mass will have ramifications on life history traits of plants. Predicted changes in temperature and precipitation, and thus in soil moisture, will affect many components of seed persistence in soil, e.g. seed longevity, dormancy release and germination, and soil pathogen activity. More/less equitable climate will alter geographic distribution for species, but restricted migratory capacity in some will greatly limit their response. Seed traits for weedy species could evolve relatively quickly to keep pace with climate change enhancing their negative environmental and economic impact. Thus, increased research in understudied ecosystems, on key issues related to seed ecology, and on evolution of seed traits in nonweedy species is needed to more fully comprehend and plan for plant responses to global warming.     

Depth selection by Daphnia pulex in response to Chaoborus kairomone

1. The presence of kairomone from the predaceous larval dipteran Chaoborus americanus can result in juvenile Daphnia pulex positioning themselves higher in the water column. Chaoborus normally lives at greater depth during the day, so this behavioural response by Daphnia will reduce its encounter rate with the predator and enhance survival. 2. Behavioural observations of seven clones from a single population were made under four treatments (with and without Chaoborus kairomone prior to and/or during experiments). 3. All clones moved higher when exposed to kairomones during behavioural observations. Six moved higher when kairomone was added prior to the experiment (i.e. pre‐conditioned), while the other clone went lower, providing evidence for the presence of genetic variation in induced behaviour. When this clone was removed from the analysis, the evidence for genetic variation in induced response disappeared. 4. Juvenile Daphnia that were pre‐conditioned had a significantly greater response than those that had no previous exposure. Of the total shift in depth (comparing treatment and control means), 38% was due to prior exposure to the kairomone (‘preconditioning’), while 62% was due to exposure during the 2‐h experiments when the depth selection was assessed. When the effect of the one clone with a qualitatively different response was removed, these two figures became 45% and 55%, respectively. 5. The enhanced effect of prior exposure to the kairomone during development suggests that such exposure causes greater sensitivity to the kairomone.     

Investigating the effects of predator removal and habitat management on nest success and breeding population size of a farmland passerine: a case study

Passerines are especially vulnerable to predation at the pre-independence stage. Although the role of nest success in British farmland passerine declines is contentious, improvement in nest success through sympathetic management could play a role in their reversal. Because habitat is known to interact with predation, management options for mitigation will need to consider effects of nest predation. We present results from an observational study of a population of Common Blackbird Turdus merula on a farm which has experienced a range of agri-environment and game-management options, including a period with nest predator control, as a case study to address some of these issues. We used an information theoretic model comparison procedure to look for evidence of interactions between habitat and nest predation, and then asked whether habitat management and nest predator abundances could explain population trends at the site through their effects on nest success. Interactions were detected between measures of predator abundance and habitat variables, and these varied with nest stage – habitat within the vicinity of the nest appeared to be important at the egg stage, and nest-placement characteristics were important at the nestling stage. Although predator control appeared to have a positive influence on Blackbird breeding population size, the non-experimental set-up meant we could not eliminate other potential explanations. Variation in breeding population size did not appear to be influenced by variation in nest success alone. Our study demonstrates that observational data can only go so far in detection of such effects, and we discuss how it might be taken further. Agri-environment and game-management techniques are likely to influence nest predation pressure on farmland passerines, but the patterns, mechanisms and importance to population processes remain not wholly understood.