Reaction norm analysis reveals rapid shifts toward delayed maturation in harvested Lake Erie yellow perch (Perca flavescens )

Harvested marine fish stocks often show a rapid and substantial decline in the age and size at maturation. Such changes can arise from multiple processes including fisheries‐induced evolution, phenotypic plasticity, and responses to environmental factors other than harvest. The relative importance of these processes could differ systematically between marine and freshwater systems. We tested for temporal shifts in the mean and within‐cohort variability of age‐ and size‐based maturation probabilities of female yellow perch (Perca flavescens Mitchill) from four management units (MUs) in Lake Erie. Lake Erie yellow perch have been commercially harvested for more than a century, and age and size at maturation have varied since sampling began in the 1980s. Our analysis compared probabilistic maturation reaction norms (PMRNs) for cohorts when abundance was lower and harvest higher (1993–1998) to cohorts when abundance was higher and harvest lower (2005–2010). PMRNs have been used in previous studies to detect signs of evolutionary change in response to harvest. Maturation size threshold increased between the early and late cohorts, and the increases were statistically significant for the youngest age in the western MU1 and for older ages in the eastern MU3. Maturation envelope widths, a measure of the variability in maturation among individuals in a cohort, also increased between early and late cohorts in the western MUs where harvest was highest. The highest rates of change in size at maturation for a given age were as large or larger than rates reported for harvested marine fishes where declines in age and size at maturation have been observed. Contrary to the general observation of earlier maturation evolving in harvested stocks, female yellow perch in Lake Erie may be rapidly evolving delayed maturation since harvest was relaxed in the late 1990s, providing a rare example of possible evolutionary recovery

Same, Similar, or Something Completely Different? Calibrating Student Surveys and Classroom Observations of Teaching Quality Onto a Common Metric

Using item response theory, this study explores whether student survey and classroom observation items can be calibrated onto a common metric of teaching quality. The data comprises 269 lessons of 141 teachers that were scored on the International Comparative Analysis of Learning and Teaching (ICALT) observation instrument and the My Teacher student survey. Using Rasch model concurrent calibration, items from both instruments were calibrated onto a common one‐dimensional metric of teaching quality. Most items were found to fit the model. Challenges pertain mainly to items measuring teaching students learning strategies and differentiation. Explanations for these difficulties are discussed

Inter-individual variability of stone marten behavioral responses to a highway

Efforts to reduce the negative impacts of roads on wildlife may be hindered if individuals within the population vary widely in their responses to roads and mitigation strategies ignore this variability. This knowledge is particularly important for medium-sized carnivores as they are vulnerable to road mortality, while also known to use available road passages (e.g., drainage culverts) for safely crossing highways. Our goal in this study was to assess whether this apparently contradictory pattern of high road-kill numbers associated with a regular use of road passages is attributable to the variation in behavioral responses toward the highway between individuals. We investigated the responses of seven radio-tracked stone martens (Martes foina) to a highway by measuring their utilization distribution, response turning angles and highway crossing patterns. We compared the observed responses to simulated movement parameterized by the observed space use and movement characteristics of each individual, but naı¨ve to the presence of the highway. Our results suggested that martens demonstrate a diversity of responses to the highway, including attraction, indifference, or avoidance. Martens also varied in their highway crossing patterns, with some crossing repeatedly at the same location (often coincident with highway passages). We suspect that the response variability derives from the individual’s familiarity of the landscape, including their awareness of highway passage locations. Because of these variable yet potentially attributable responses, we support the use of exclusionary fencing to guide transient (e.g., dispersers) individuals to existing passages to reduce the road-kill risk

Comparative population genetic structure of the endangered southern brown bandicoot, Isoodon obesulus, in fragmented landscapes of Southern Australia

Genetic connectivity is a key factor for maintaining the persistence of populations in fragmented landscapes. In highly modified landscapes such us peri-urban areas, organisms' dispersal among fragmented habitat patches can be reduced due to the surrounding matrix, leading to subsequent decreased gene flow and increased potential extinction risk in isolated sub-populations. However, few studies have compared within species how dispersal/gene flow varies between regions and among different forms of matrix that might be encountered. In the current study, we investigated gene flow and dispersal in an endangered marsupial, the southern brown bandicoot (Isoodon obesulus) in a heavily modified peri-urban landscape in South Australia, Australia. We used 14 microsatellite markers to genotype 254 individuals which were sampled from 15 sites. Analyses revealed significant genetic structure. Our analyses also indicated that dispersal was mostly limited to neighbouring sites. Comparisons of these results with analyses of a different population of the same species revealed that gene flow/dispersal was more limited in this peri-urban landscape than in a pine plantation landscape approximately 400 km to the south-east. These findings increase our understanding of how the nature of fragmentation can lead to profound differences in levels of genetic connectivity among populations of the same species.You Li, Steven J.B. Cooper, Melanie L. Lancaster, Jasmin G. Packer, Susan M. Carthe

3D velocity measurement of fertiliser with an optical sensor : practical issues

Nowadays, one of the most important objective in fertiliser centrifugal spreading research is the best prediction of spatial distribution of fertiliser on the ground. This is explained by the great number of spreading settings solutions (which can be used in a unit way or in combinations), and by the very important panel of fertiliser characteristics. All different combinations can't be tested with real test bench trials, so good prediction devices should be very interesting for researchers and manufacturers in order to determine experimental spreading characteristics, validate new solutions, draw up setting tables. The spatial prediction of fertiliser on the ground is computed by using a ballistic flight model (fig. 1). The first objective of our research is to validate the data sensor obtained, in order to envisage its integration on a real spreader

High-throughput phenotyping technology for maize roots

This paper describes the development of high-throughput measurement techniques allowing acquisition of phenotypical data describing maize roots. One of a maize root's traits is the level of complexity, which was expressed in a Fractal Dimension (FD) calculated from root images. Another important trait is the Root Top Angle (RTA) that was measured using a new machine vision algorithm. The measurement system consisted of a semi-automated imaging box that provided a highly diffuse lighting scene and allowing imaging of up to 700 roots per day. The measurement techniques were evaluated using roots recovered from a set of 200 recombinant inbred lines (RILs) derived from a cross between maize inbreds B73 and CML333. B73 and CML333 are known to have different root characteristics and their progeny are expected to show segregation for root traits. Since standard protocols for the measurement of the two root traits are non-existent, no comparisons could be made. Nevertheless, the data showed that the techniques were capable of confirming significant differences in FD among the two inbred lines and their progeny, as well as measuring variations in RTA that are known for the inbreds and their crosses. In addition, first hypotheses about the inheritance of root complexity (as expressed in the FD) and RTA in maize were derived and tested: initial evidence showed that root complexity is a phenotype probably determined by a multitude of genes with small effects. In contrast, the data indicated that the RTA is additively inherited