Comparison of the different effects of BEP (red), E-<i>β</i>-ocimene (blue) and real brood (black) on worker physiology and behaviour.

<p>(dotted line: low pheromone production).</p

E-<i>β</i>-ocimene emission by the brood during 20 minutes.

<p>A. as ng per individual. B. as ng per mg of individual. (Different letters indicate significant differences in individual E-<i>β</i>-ocimene emission (P<0.05) (n≥4), cross: mean, box: 25%–75%; line in the box: median, whisker: Min-Max, //: larvae cell capping).</p

Quantitative analysis of the phoretic <i>Varroa</i> infestation.

<p>(<b>A</b>) Varroa prevalence. The proportion of colonies where mites could be retrieved (black) versus not retrieved (white) is presented in terms of the sampling site location and number of years <i>Varroa</i> had been detected in the area. A significant increase in <i>Varroa</i> prevalence along the sampling transect is symbolised by the red curve (GLMM, Z = 4.14, p<0.001, 27≤n≤39). (<b>B</b>) <i>Varroa</i> infestation levels according to the number of years of confirmed exposure to <i>Varroa</i>. Number of phoretic mites per 100 bees (27≤n≤39). Stars indicate significant differences between years of infestation (Pairwise post-hoc comparisons, p<0.01).</p

Contingency table analyses for virus co-prevalence in both bees and mite samples.

<p>For the <i>Varroa</i>-infested region, separate comparisons were made for the virus prevalences and co-infection in bee samples and in mite samples (n = 41). The contingency tables were derived through comparing the observed incidence of co-infection with the expected values derived from the individual prevalences in bees and mites. For significant non-random associations (bold; p<0.05) is also indicated whether the association is positive (+), i.e. a higher incidence of co-infection than expected, or negative (−), i.e. a lower incidence of co-infection than expected.</p

Principal component analyses of pathogen titres in honeybee and <i>Varroa</i> samples.

<p>(<b>A</b>) Barplot of the eigenvectors of the PCA performed on the variables measured in bees. Variables included in the Principal Component Analysis (PCA) are the titres of 5 viruses (DWV, BQCV, CBPV, KBV, SBV) and the <i>Varroa</i> infestation rate (Var). Numbers above each bar indicate the cumulative percentage of variability explained by the successive eigenvectors. The two principal eigenvectors, represented by black bars, correspond to the axes used to plot the colonies in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004323#ppat-1004323-g004" target="_blank">Figure 4.B</a>. (<b>B</b>) Scatterplot of colonies analysed by PCA for the titres of 5 viruses plus the <i>Varroa</i> infestation rates in bees (n = 191). The colony values for the two principal components are plotted, with each colony represented by a filled circle. The colonies are clustered by colour and bound by an ellipse according to the number of years since the first detection of <i>Varroa</i>, indicated by the number located at the centre of gravity of each ellipse. The ellipse covers 67% of the samples belonging to the cluster. The colour code is the same as for <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004323#ppat-1004323-g001" target="_blank">Figure 1</a>. (<b>C</b>) Barplot of the eigenvectors of the PCA performed on variables measured in bees and in <i>Varroa</i>. Variables included in the PCA are the titres of 4 virus species in bees (DWV, BQCV, KBV, SBV), titres of 4 virus species in <i>Varroa</i> (DWV.V, BQCV.V, KBV.V, SBV.V) and the <i>Varroa</i> infestation rates (Var). The numbers above each bar indicate the cumulative percentage of variability explained by the successive eigenvectors. The two principal eigenvectors, represented by the black bars, correspond to the axes used to plot the colonies in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004323#ppat-1004323-g004" target="_blank">Figure 4.D</a>. (<b>D</b>) Scatterplot of colonies analysed by PCA for virus titres in bees and mites plus the <i>Varroa</i> infestation rates (n = 83). The colony values for the two principal components are plotted, with each colony represented by a filled circle. The colonies are clustered by colour and bound by an ellipse, according to the number of years since the first detection of <i>Varroa</i>. Each ellipse covers 67% of the samples belonging to the cluster.</p

Map illustrating the spread of <i>Varroa</i> across New Zealand and the location of sampling sites.

<p>Colours indicate the date <i>Varroa</i> was first confirmed in each area. Shaded tones from dark red to light yellow show the progression of the front of <i>Varroa</i> infestation. Control regions where the mite had not yet been detected are presented in white. Black dots indicate the location of the apiaries sampled in each region. The sampling transect crosses the front of infestation.</p

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Honeybee virus prevalence across the <i>Varroa</i> front of infestation.

<p>Pathogen prevalence across the front of infestation, in bee samples and <i>Varroa</i> mite samples. The percentage of colonies assigned positive for each of the seven viruses monitored is compared between <i>Varroa</i>-free areas for bee samples (white bars, n = 39), <i>Varroa</i>-infested areas for bee samples (black bars, n = 75), and <i>Varroa</i> mite samples (grey bars, n = 34). Stars indicate significant differences between proportions (Chi-square, p<0.05). Viruses are presented in decreasing order of prevalence. The average pathogen prevalence in bee samples across all regions sampled is indicated on the x-axis below the pathogen acronym.</p

Virus titres in honeybees and <i>Varroa</i> mites along the <i>Varroa</i> front of expansion.

<p>(<b>A</b>) DWV titres in bees (Log₁₀ DWV copies/bee) according to the number of years of exposure to <i>Varroa</i>. A significant increase in the level of viral infestation was detected along the sampling transect (GLMM, t = 3.78, p<0.001, 30≤n≤41). (<b>B</b>) DWV titres in <i>Varroa</i> (Log₁₀ DWV copies/mite) according to the number of years of confirmed exposure to <i>Varroa</i>. A significant increase in the level of viral infestation was detected along the sampling transect (GLMM, t = 4.55, p<10⁻⁵). (<b>C</b>) BQCV titres in bees (Log₁₀ BQCV copies/bee) according to the number of years of exposure to <i>Varroa</i>. A significant increase in the level of viral infestation was detected along the sampling transect (GLMM, t = 3.35, p<0.001, 30≤n≤41). (<b>D</b>) KBV titres in bees (Log₁₀ KBV copies/bee) according to the number of years of exposure to <i>Varroa</i>. (<b>E</b>) SBV titres in bees (Log₁₀ SBV copies/bee) according to the number of years of exposure to <i>Varroa</i>. (<b>F</b>) CBPV titres in bees (Log₁₀ CBPV copies/bee) according to the number of years of exposure to <i>Varroa</i>.</p

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