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

Homing abilities of the Australian intertidal ant Polyrhachis sokolova

The pressure of returning to and locating the nest after a successful foraging trip is immense in ants. To find their way back home, ants use a number of different strategies (e.g. path integration, trail following) and rely on a range of cues (e.g. patt

Head roll stabilisation in the nocturnal bull ant Myrmecia pyriformis: implications for visual navigation

Ant foragers are known to memorise visual scenes that allow them to repeatedly travel along idiosyncratic routes and to return to specific places. Guidance is provided by a comparison between visual memories and current views, which critically depends on how well the attitude of the visual system is controlled. Here we show that nocturnal bull ants stabilise their head to varying degrees against locomotion-induced body roll movements and this ability decreases as light levels fall. There are always un-compensated head roll oscillations that match the frequency of the stride-cycle. Head roll stabilisation involves both visual and non-visual cues as ants compensate for body roll in complete darkness and also respond with head roll movements when confronted with visual pattern oscillations. We show that imperfect head roll control degrades navigation-relevant visual information and discuss ways in which navigating ants may deal with this problem

Vision and navigation in nocturnal ants

The ability to navigate between places of importance is fundamental for all animals be it for foraging on a daily basis or for migrating seasonally from and to mating or feeding grounds. Central-place foragers, such as ants, have to regularly navigate between their nest and food sources every day, often covering 1000 times their body length. Ants have occupied almost every environment on earth, from barren deserts to the dense understory of rainforests and they are active during both day and night. The navigational cues available in these different environmental and temporal niches are radically different. This makes it possible to study the mechanisms underlying navigation in both closely and distantly related species by comparing (1) their reliance on different navigational cues between different niches, (2) how their sensory systems have adapted to perceive and capture the information they need and (3) how their brains process the information, which ultimately drives behaviour. This combination of the disciplines of ethology, evolutionary biology and neuroscience is commonly referred to as neuroethology and aims at studying the mechanisms underlying animal behaviour in the context in which they have evolved. Ants repeatedly return to places of interest by first memorising the visual scene around it. On their return trips they move and compare their current views to a stored memory image to pinpoint specific locations. For this, animals require a stable image. The robustness of visual information needed to compare memorised and current views is prone to degradation by both locomotion-induced blurring and also by environmental factors such as falling light levels. In the first part of my thesis, I address how nocturnal bull ants, Myrmecia pyriformis, stabilise their head to varying degrees of locomotion-induced body roll at a range of light intensities. I demonstrate through experiments in the animals' natural habitat and in laboratory conditions using highspeed videography that their ability to stabilise their head decreases as light levels drop. This clearly indicates that vision plays a role in head stabilisation in these ants. I discuss the consequences of imperfect head roll for visually guided navigation. In the second part of my thesis I describe techniques in histology, neuroanatomy and behavioural ecology that I learnt to understand the underlying mechanisms of navigation in nocturnal ants

Formulierungen von ätherischen Ölen zur Regulierung des Rapsglanzkäfers (Meligethes spp.)

Different formulations of repellent essential oils were developed in order to control Pollen beetles. Odour release rate over time of different formulations was analyzed b gas-chromatography

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 decisions necessary to strike this balance are often based on information that is inherently imperfect and inc

Habituation under natural conditions: model predators are distinguished by approach direction

Habituation is an active process that allows animals to learn to identify repeated, harmless events, and so could help individuals deal with the trade-off between reducing the risk of predation and minimizing escape costs. Safe habituation requires an accurate distinction between dangerous and harmless events, but in natural environments such an assessment is challenging because sensory information is often noisy and limited. What, then, comprises the information animals use to recognize objects that they have previously learned to be harmless? We tested whether the fiddler crab Uca vomeris distinguishes objects purely by their sensory signature or whether identification also involves more complex attributes such as the direction from which an object approaches. We found that crabs habituated their escape responses after repeated presentations of a dummy predator consistently approaching from the same compass direction. Females habituated both movement towards the burrow and descent into the burrow, whereas males only habituated descent into the burrow. The crabs were more likely to respond again when a physically identical dummy approached them from a new compass direction. The crabs distinguished between the two dummies even though both dummies were visible for the entire duration of the experiment and there was no difference in the timing of the dummies' movements. Thus, the position or approach direction of a dummy encodes important information that allows animals to identify an event and habituate to it. These results argue against the traditional notion that habituation is a simple, nonassociative learning process, and instead suggest that habituation is very selective and uses information to distinguish between objects that is not available from the sensory signature of the object itself

Individual foraging patterns of the jack jumper ant Myrmecia croslandi (Hymenoptera: Formicidae)

In ants, we know most about the foraging patterns at the colony level. We know surprisingly little about the foraging behaviour of individual foragers and how they shape the behaviour of the colony. To identify spatial and temporal varia-tion in foragin