Landscape complexity benefits bumble bee visitation in faba bean (Vicia faba minor L.) but crop productivity is not pollinator-dependent

Faba bean (Vicia faba minor L.) is partially dependent on insects for pollination, but the degree of pollinatordependency and whether crop productivity is limited by insufficient insect pollination remain unknown. We monitored insect pollinators and their foraging behaviors (i. e., legitimate flower visitation, nectar robbing and extra-floral nectary visitation) in a total of 20 faba bean fields of a single cultivar (Tiffany) 2018?2019. Focal fields were situated along a gradient of landscape complexity. In each field, a pollination experiment was established, where plants were either bagged to exclude pollination by insects or remained open for pollinator visits. In addition, all flowers on half of the bagged and open-pollinated plants were pollinated by hand to measure the degree of pollen limitation. We found that bumble bee abundance was higher, and legitimate flower visitor abundance tended to be higher, in complex landscapes with more semi-natural habitat, indicating that the faba bean pollination potential is higher in complex landscapes. The pollination experiment showed that the number of beans per pod was lower in bagged plants compared with other treatments in one of the years, but the lower number of beans per pod was compensated for by a higher individual bean weight, such that there was no pollinator-dependency or effect of hand pollination on total bean mass per plant. We conclude that to be able to characterize the value of insect pollination services in faba bean we need an improved understanding of how pollinator-dependency varies across modern cultivars, and how environmental conditions can increase or, as in our case, cancel this pollinator-dependency

Flicker is part of a multi-cue response criterion in fiddler crab predator avoidance.

Predator avoidance behaviour costs time, energy and opportunities, and prey animals need to balance these costs with the risk of predation. The necessary decisions to strike this balance are often based on information that is inherently imperfect and incomplete due to the limited sensory capabilities of prey animals. Our knowledge, however, about how prey animals solve the challenging task of restricting their responses to the most dangerous stimuli in their environment, is very limited. Using dummy predators, we examined the contribution of visual flicker to the predator avoidance response of the fiddler crab Uca vomeris. The results illustrate that crabs let purely black or purely white dummies approach significantly closer than black-and-white flickering dummies. We show that this effect complements other factors that modulate escape timing such as retinal speed and the crab's distance to its burrow, and is therefore not exclusively due to an earlier detection of the flickering signal. By combining and adjusting a range of imperfect response criteria in a way that relates to actual threats in their natural environment, prey animals may be able to measure risk and adjust their responses more efficiently - even under difficult or noisy sensory conditions