Selecting suitable sites for animal waste application using a raster GIS

Rapid growth of intensive animal industries in southeast Queensland, Australia, has led to large volumes of animal waste production, which posses serious environmental problems in the Murray Darling Basin (MDB). This study presents a method of selecting sites for the safe application of animal waste as fertiliser to agricultural land. A site suitability map for the Westbrook subcatchment within the MDB was created using a geographic information system (GIS)-based weighted linear combination (WLC) model. The factors affecting the suitability of a site for animal waste application were selected, and digital data sets derived from up to 1:50,000 scale maps were acquired. After initial preprocessing, digital data sets were clipped to the size of the delineated subcatchment boundary producing input factors. These input factors were weighted using the analytical hierarchy process (AHP) that employed an objectives-oriented comparison (OOC) technique to formulate the pairwise comparison matrix. The OOC technique, which is capable of deriving factor weight independently, formulated the weight derivation process by making it more logical and systematic. The factor attributes were classified into multiple classes and weighted using the AHP. The effects of the number of input factors and factor weighting on the areal extent and the degree of site suitability were examined. Due to the presence of large nonagricultural and residential areas in the subcatchment, only 16% of the area was found suitable for animal waste application. The areal extent resulting from this site suitability assessment was found to be dependent on the areal constraints imposed on each input factor, while the degree of suitability was principally a function of the weight distribution between the factors.     

The scent of dominance: female field crickets use odour to predict the outcome of male competition

Pheromones may convey information about mate quality and social status. In the field cricket Gryllus integer, females mount the males for copulation, such that males cannot coerce females to mate. We examined whether virgin G. integer females preferred the scent of potentially dominant males to that of subordinate males. First, we collected pheromones by confining males on filter paper. Next, we offered filter paper from each of two size-matched males and control paper to females that had never been exposed to males, and measured the time spent by the female on each kind of paper. Finally, dominance status of the males in each size-matched pair was determined by pitting the two males against one another in agonistic contests. When offered filter paper from subsequently dominant versus subsequently subordinate males, females spent more time on the paper from the dominant male than the subordinate male, and much less time on control paper. Thus, pheromones may inform female G. integer about a male's potential to achieve dominant social status. Male pheromones were also associated with the female's tendency to mount a male. In contrast to cockroaches, where females prefer the scent of subordinate males (presumably to avoid risk of injury), female crickets prefer the scent of potentially dominant males and are more likely than males to wound their mating partners.     

Colony nutritional status modulates worker responses to foraging recruitment pheromone in the bumblebee Bombus terrestris

Foraging activity in social insects should be regulated by colony nutritional status and food availability, such that both the emission of, and response to, recruitment signals depend on current conditions. Using fully automatic radio-frequency identification (RFID) technology to follow the foraging activity of tagged bumblebees (Bombus terrestris) during 16,000 foraging bouts, we tested whether the cue provided by stored food (the number of full honeypots) could modulate the response of workers to the recruitment pheromone signal. Artificial foraging pheromones were applied to colonies with varied levels of food reserves. The response to recruitment pheromones was stronger in colonies with low food, resulting in more workers becoming active and more foraging bouts being performed. In addition to previous reports showing that in colonies with low food successful foragers perform more excited runs during which they release recruitment pheromone and inactive workers are more prone to leave the nest following nectar influx, our results indicate that evolution has shaped a third pathway that modulates bumblebee foraging activity, thus preventing needless energy expenditure and exposure to risk when food stores are already high. This new feedback loop is intriguing since it involves context-dependent response to a signal. It highlights the integration of information from both forager-released pheromones (signal) and nutritional status (cue) that occurs within individual workers before making the decision to start foraging. Our results support the emerging view that responses to pheromones may be less hardwired than commonly acknowledged. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A population comparison of the strength and persistence of innate colour preference and learning speed in the bumblebee <Emphasis Type="Italic">Bombus terrestris</Emphasis>

Studies of innate colour preference and learning ability have focused on differences at the species level, rather than variation among populations of a single species. Initial strength and persistence of colour preferences are likely to affect colour choices of naïve flower visitors. We therefore study the influence of both the strength and persistence of innate colour preference (for blue) on an operant learning task (associating food reward with yellow flowers) in two populations of the bumblebee Bombus terrestris. We found that both strength and persistence of blue preference differed significantly between populations: B. terrestris dalmatinus had a weaker and less persistent blue preference than B. terrestris audax. These differences in preference also influenced learning performance. Considering only landing behaviours, one-trial learning occurred in the majority (73%) of bees, and was achieved sooner in B. terrestris dalmatinus because of its weaker blue preference. However, compared to landing behaviours the relative frequency of approach flights to rewarding and unrewarding flower types changed more slowly with task experience in both populations. When considering both approaches and landings, the rate of learning, following the first rewarded learning trial, was faster in B. terrestris audax than B. terrestris dalmatinus. However, the net effects of population differences in blue preference and learning dynamics result in similar final levels of task performance. Our results provide new evidence of behavioural differences among isolated populations within a single species, and raise intriguing questions about the ecological significance and adaptive nature of colour preference.     

An evaluation of the applicability of microarrays for monitoring toxic algae in Irish coastal waters

The applicability of microarrays to monitor harmful algae across a broad range of ecological niches and toxic species responsible for harmful algal events has been one of the key tasks in the EU Seventh Framework Programme (FP7)-funded Microarrays for the Detection of Toxic Algae project. The technique has a strong potential for improving speed and accuracy of the identification of harmful algae and their toxins to assist monitoring programmes. Water samples were collected from a number of coastal sites around Ireland, including several that are used in the Irish National Phytoplankton and Biotoxin Monitoring Programme. Ribosomal RNA was extracted from filtered field samples, labelled with a fluorescent dye, and hybridised to probes spotted in a microarray format on a glass slide. The fluorescent signal intensity of the hybridisation to >120 probes on the chip was analysed and compared with actual field counts. There was a general agreement between cell counts and microarray signal. Results are presented for field samples taken from a range of stations along the Irish coastline known for harmful algal events during the first field trial (July 2009–April 2010).     

Nymphal density, behavioral development, and life history in a field cricket

Population density regulates the strength of intraspecific competition and may thereby be reflected in life-history variables, such as development time, growth rate, or investment in immune defense. However, population density may also affect the fitness payoffs of different behaviors and consequently shape the development of personality. Here we studied if population density during nymphal development (one, four, or ten individuals raised together) affects the level of boldness, measured as the latency time to recover from freezing and emerge from a shelter, aggressiveness towards conspecifics or their correlation at the adult stage in the field crickets, Gryllus integer. In addition, we tested if individuals invest more resources in immune function or speed up their development in response to a high conspecifics density during ontogeny. Nymphal density did not affect adult boldness or aggressiveness towards conspecific males per se, but these variables showed a negative association, i.e., indicated an unconventional behavioral syndrome in the highest density treatment. Supporting the effectiveness of density treatments in inducing plastic responses, individuals reached maturity sooner and invested more resources in immune function in the highest nymphal density group compared to groups consisting of one or four individuals. Our results suggest that population density may play an important role in shaping both the realized life history and development of behavioral syndromes.