Observed (o) and predicted (line) cumulative number of recaptured <i>P. melanarius</i> as a function of time.

<p>Predicted values were simulated with the calibrated model that had most support from the data (model 1, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115751#pone-0115751-t001" target="_blank">Table 1</a>). Panels on the left (a–c) are for beetles released in oilseed radish, on the right (d–f) for beetles released in rye. Error-bars show the 95% confidence interval of the observations.</p

Time evolution of the distribution of <i>Pterostichus melanarius</i> in two adjacent crops simulated with a Fokker-Planck diffusion model (model 1, Table 1) that had a common value of motility for both crops (215 m² d⁻¹) and preferential movement at the interface equivalent to a beetle on the interface moving to oilseed radish with a probability of 0.60 and moving to rye with a probability of 0.40.

<p>Beetle densities varied between 0.42 m⁻² on day 1 to 0.008 m⁻² on day 21. Beetles densities in the slow-release margins that surrounded the experimental field were omitted. Crosses and dots in the upper left panel mark the locations at which beetles in the model were released and recaptured, respectively.</p

Distribution of <i>P. melanarius</i> along the length of the field over time simulated with the model that had most support from the data (model 1, Table 1).

<p>The Y-axis represents the total number of beetles over the width of the field. On day 0, 1015 beetles were released at each black dot. Number of beetles in the slow-release margins that surround the field are not shown.</p

Model selection among variants of the <i>Fokker-Planck</i> diffusion model describing beetle dispersal in the field experiment.

<p>A single parameter value is shown when habitats or trap types were not distinguished in a model variant. The value of <i>π</i>₁ is 1 throughout. If no value for <i>π</i>₂ is shown, it was set to 1 and not included in the calibration. The negative log-likelihood (NLL) is a measure of the goodness of fit of the model to the data. ΔAIC is the difference in Akaike's information criterion between a model variant and the model variant with most support of the data (model 1). Models variants of which the ΔAIC is smaller than two are considered equivalent and have equal support from the data.</p><p><i>μ</i>₁: motility in oilseed radish; <i>μ</i>₂: motility in rye; <i>ξ</i>: relative loss rate due to removal other than recapture (e.g. mark wear and mortality); <i>ω</i>₀: trap-coefficient for trapping stations without screens; <i>ω</i>₁: trap-coefficient for trapping stations with screens; <i>π</i>₁: multiplication factor of the flux of beetles from oilseed radish to rye; <i>π</i>₂: multiplication factor of the flux of beetles from rye to oilseed radish.</p><p>Model selection among variants of the <i>Fokker-Planck</i> diffusion model describing beetle dispersal in the field experiment.</p

Examples of movement tracks for a starved <i>Pterostichus melanarius</i> beetle with low motility (7 cm² s⁻¹; left) and for a fed beetle with a high motility (88 cm² s⁻¹; right).

<p>The total time spent in the arena's interior was 24.8 min for the starved and 11.7 min for the fed beetle. Moves in the 10 cm edge zone are represented by thin grey lines.</p

Simulated change in time of the number of marked beetles in the field and the slow-release boundaries, and the change in number of beetles that were either captured or lost due to mark wear or death.

<p>Simulations were made with the model that had most support from the data (model 1, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115751#pone-0115751-t001" target="_blank">Table 1</a>). At Time  = 0, a total of 2030 virtual beetles were released.</p

Spatial layout of the field experiment at Droevendaal organic experimental farm in Wageningen, the Netherlands.

<p><i>Pterostichus melanarius</i> were released at the long vertical lines and recaptured at trapping stations with (|•, •|) or without (•) screens.</p

Representation of fluxes in the <i>x-</i>direction in the spatial simulation model.

<p><i>N</i> (<i>x,y,t</i>) is the density of beetles (m⁻²) in a grid cell with coordinates (<i>x,y</i>) at time <i>t. μ</i>₁ and <i>μ₂</i> (m² d⁻¹) are the motilities of beetles in oilseed radish and rye, respectively. <i>π</i>₁ and <i>π</i>₂ are dimensionless and modify the fluxes of beetles between the two habitats.</p

Distribution of observed (o) and predicted (line) number of <i>P. melanarius</i> recaptured along the length of the experimental field, cumulated over time and over the width of the field for (a) beetles released in oilseed radish at 50 m and (b) beetles released in rye at 70 m. Predicted values are simulated with the model that had most support from the data (model 1, Table 1).

<p>The error-bars show the 95% CI of the observations. Averaging of densities at a given <i>x</i> was done over all traps at that <i>x</i>-value. At x = 50 and 70 m, there were no traps close to the release points, causing a drop in the catch, both in the data and the fitted model. Cf. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115751#pone-0115751-g001" target="_blank">Fig. 1</a> for trap locations.</p

Average movement parameters (± se) of <i>P. melanarius</i> in an arena experiment with hunger level, gender and crop species as factors.

<p>Number of observations per factor are indicated in the column headings. Beetles were recorded for 50 min in arenas of 5 m². <i>P</i>-values in bold indicate significant differences (<i>p</i><0.05) between treatment groups.</p><p>*F statistic, n.d.f. = 1 for all tests.</p><p>Average movement parameters (± se) of <i>P. melanarius</i> in an arena experiment with hunger level, gender and crop species as factors.</p