Vosteen et al. 2016_R Skript_Fig. 3 honeydew attractivity

Fig. 3 – hoverfly oviposition experiment: To test which cues elicit hoverfly oviposition under field conditions, eggs were counted on plants that were previously aphid infested, non-infested plants treated with aphid honeydew and non-treated control plants in the presence and absence of pea aphids. Plants were left for 30 h in the field and hoverfly eggs were counted afterwards. A randomized block design was used in this experiments. Each block consisted of all six treatments. Number of hoverfly eggs was analyzed with a generalized linear mixed effects model with a poisson error distribution, using blocks as random effects (random intercept) and treatments as fixed effects. P-values for explanatory variables were obtained by sequentially deleting explanatory variables and comparison of the more complex model with the simpler model with a likelihood ratio test (Zuur et al. 2009). Factor level reductions were used to reveal differences between levels of a treatment (Crawley 2013).