Yield and its components
Lack of pollination (P-) decreased total bean weight per plant, mean number of beans per pod and total number of beans per plant, independently of the herbivory treatment (Table 1, Fig. 1b,c, Fig. S4). In the absence of insect pollination, bean weight and number of beans per plant decreased by 15% and 17%, respectively. There was a marginal (p= 0.06) interactive effect of pollination and herbivory on individual bean weight, with pollination increasing individual bean weight but only in the absence of herbivory (Table 1, Fig. 1a, Fig. S4). Herbivory increased percent damaged beans, with on average 39% damaged beans in the H+ treatment (Table 1, Fig. S3), which is over tenfold the economic injury threshold set for beans targeting human consumption and could lead to up to 78% economical losses (Bachmann et al., 2020; Roubinet, 2016). There was no effect of pollination nor herbivory treatments on yield (kg.ha-1), or mature or total number of pods per plant, however, proportion of mature pods was lower with lack of pollination, due to higher numbers of unfertilized and immature pods (Table 1, Fig. 1d, Fig. S4).
When herbivory damage on each plant was used as an explanatory variable (% Damage), there were interactive effects of pollination and herbivory damage on individual bean weight, total bean weight per plant, and number of beans per pod (Table 1, Fig. 2, Fig. S5). In the absence of pollination, there were positive relationships between yield and herbivory damage for several yield components (individual bean weight: est=0.001, se=0.0004, p<0.01; total bean weight: est=0.06, se=0.02, p<0.01; and number of beans per pod: est=0.007, se=0.002, p<0.01) (Fig. 2, Fig. S5). In the presence of insect pollination, there were no relationships with herbivory damage. In addition, number of beans per plant increased with increasing herbivory damage independent of pollination treatment (Table 1). Number of pods per plant was not affected, but proportion of mature pods increased with herbivory damage due to a decrease in the number of unfertilized and immature pods (Table 1).