Neurons against Noise : Neural adaptations for dim light vision in hawkmoths

All animals perceive the world through their senses, which form the basis for their decisions and motor actions. However, when these all-important senses reach their limit and cease to provide reliable information, the animal’s survival is threatened. Among the senses, vision is brought to its limits on a daily basis, because its signal strength is diminished as night falls, and increases again as the sun rises. In this thesis, I investigated adaptations that enable the visual system of hawkmoths, a group of insects, to cope with the low light intensities they face at night. I have focused on neural adaptations, manifested in the processing of visual neurons, in contrast to anatomical adaptations, such as modifications of the eye. I showed that neural adaptations exist in the motion vision system of hawkmoths, in the form of integration of visual information in space and time. Furthermore, I demonstrated that a combination of such spatial and temporal summation increased sensitivity and information content in dim light (Paper I). The amount of spatial and temporal summation matched the ecological needs of different hawkmoth species, as well as their anatomical adaptations for visual sensitivity: night active species, and species with less sensitive eyes had more extensive spatial and temporal summation than day-active species and species with very sensitive optics (Paper II). Furthermore, I identified and characterised candidate neurons that carry out spatial and temporal summation in the brain of hawkmoths (Paper III). Finally, I quantified the effects of temporal summation on the ability of hawkmoths to track flowers in hovering flight at different light levels, and showed that a subset of the observed behavioural phenomena could be explained by temporal processing in the nervous system (Paper IV). Taken together, this work has provided detailed insight into how neural processing can increase visual reliability in dim light. The results presented are not only relevant to hawkmoths, since neural summation is also expected to increase visual sensitivity in other species of nocturnal insects, and can be compared to similar mechanisms in vertebrates. Furthermore, this work is instructive for the development of artificial visual systems, for which insect brains have proven to be a successful biomimetic model

A glass half empty: Assessing the impact of empty flowers on foraging behaviour in three bee species

Flower-visiting insects face the difficult choice of selecting which flowers to visit and which to ignore. Foraging becomes more complicated because flowers can sometimes stop offering nectar, either due to removal by other visitors or because of physiological changes in the plant. In humans, items that are unexpectedly unavailable at the time of choice are called ‘phantom decoys’ and have been shown to influence preference relationships between other items in the choice set. If phantom decoys occur in pollinating insects, then the presence of empty flowers could have community-wide impacts on visitation rates of neighbouring flowers. In my first chapter, we tested if European honeybees Apis mellifera were susceptible to phantom decoy-style empty flowers. We then tested the effects of empty flowers on Bombus impatiens when they were influenced by the choices of their conspecifics. Finally, we tested if stingless bees, Tetragonula carbonaria made use of floral colour generalisations to choose flowers when the best flower in the choice set had its nectar removed. Overall, while we saw minimal impacts on floral choice by empty flowers, we did show that social behaviour is a key driver in allowing bees to make effective foraging decisions in the presence of empty flowers, and empty flowers can result in the abandonment of patches

The Ecology of a Tallgrass Treasure: Audubon’s Spring Creek Prairie

This book describes the major plant and animal components of Spring Creek Prairie Audubon Center, an 850-acre National Audubon Society tallgrass prairie in Lancaster County, southeastern Nebraska. In addition to providing a species list of the area’s plants (368 species), there are comprehensive annotated lists of its birds (240), mammals (43), reptiles (23), and amphibians (10). There are also variably complete annotated lists of the area’s butterflies (76), sphinx moths (30), silk moths (7), dragonflies (24), damselflies (11), grasshoppers (9), katydids (11), mantids (2), and walkingsticks (2). Brief profiles of life histories and ecologies of 55 animal and 7 plant species are included, as well as information on nearly 100 public-access native grasslands in eastern Nebraska. The text comprises more than 68,000 words, 400 references, and a glossary of 125 biological/scientific terms as well as more than 40 line drawings by the author. doi 10.13014/K25B00NKhttps://digitalcommons.unl.edu/zeabook/1066/thumbnail.jp

The assessment report of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services on pollinators, pollination and food production

The thematic assessment of pollinators, pollination and food production carried out under the auspices of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services aims to assess animal pollination as a regulating ecosystem service underpinning food production in the context of its contribution to nature’s gifts to people and supporting a good quality of life. To achieve this, it focuses on the role of native and managed pollinators, the status and trends of pollinators and pollinator-plant networks and pollination, drivers of change, impacts on human well-being, food production in response to pollination declines and deficits and the effectiveness of responses