199 research outputs found

    Biologically inspired radar and sonar target classification

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    Classification of targets is a key problem of modern radar and sonar systems. This is an activity carried out with great success by echolocating mammals, such as bats, that have evolved echolocation as a means of detecting, selecting and attacking prey over a period of more than 50 million years. Because they have developed a highly sophisticated capability on which they depend for their survival, it is likely that there is potentially a great deal that can be learnt from understanding how they use this capability and how this might be valuably applied to radar and sonar systems. Bat-pollinated plants and their flowers represent a very interesting class of organisms for the study of target classification as it is thought that co-evolution has shaped bat-pollinated flowers in order to ease classification by bats. In this thesis, the strategy that underpins classification of flowers by bats is investigated. An acoustic radar has been developed to collect data to perform a floral echoes analysis. Results show that there is a relative relevance of specific parts of the flower in displaying information to bats and show that there are different characteristics in the flowers' echo fingerprints, depending on age and stage of maturity, that bats might use to choose the most suitable flowers for pollination. We show that, as suggested by the oral echoes analysis, a more intelligent way to perform target classification can result in improved classification performance and, investigate biologically inspired methods and ideas that might become important tools for the study and the development of radar and sonar target classification

    Pollination ecology of Agave palmeri in New Mexico, and landscape use of Leptonycteris nivalis in relation to Agaves

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    Where animals spend time can provide important clues to their ecological needs, but this information is very difficult to obtain for small volant animals. The research described in Chapter 1 was an attempt to discern how L. nivalis utilize the landscape in relation to the distribution of Agave havardiana in Big Bend National Park, Texas. I found that although the landscape use of Leptonycteris nivalis is centered on habitat with high concentrations of blooming A.havardiana, it is not restricted to those areas, and furthermore adults and juveniles may differ in their behavior. Adult females may remain near food sources in order to replenish energy stores lost to migration and the demands of reproduction, whereas juveniles may feed early in the evening and then undertake occasional far-reaching expeditions, perhaps in order to create a navigational map. If this behavior is widespread among juveniles, it emphasizes the need to carefully assess the risk of constructing wind-turbine energy facilities not just within agave-rich habitat, but anywhere near the range of this endangered bat species. The research described in Chapter 2 focused on documenting the importance of flowering agaves as a food resource for the many vertebrate and invertebrate, diurnal and nocturnal visitors. I found that A. palmeri was visited by a wide variety of vertebrate and invertebrate visitors, many of which are pollinators of other plants, and that there was considerable variation in visitation rates in space and time - in fact, bats were not even observed at one of the study sites. Increased visitation was associated with larger plant sizes for all visitor types assessed. In Chapter 3, I explored how the fruit and seed production of A. palmeri at these three sites were affected by the plants morphology, phenology (timing of bloom), prior reproductive success, and the patterns of visitation by different animal guilds. Models indicated that bats were the most effective visitors, because periods with high bat visitation rates also had very high seed. Periods with high bird visitation resulted in many fruits but with poor seed set, possibly indicating that they are responsible for some degree of reproduction, though the exact mechanism is not clear. Floral branch position interacted in a complex manner with prior fruit set, affecting fruit set, seed set, and mean seed mass. Plants with high prior fruit set showed decreased seed set in fruits on late-blooming branches, possibly indicative of resource limitation

    Adaptive evolution of butterfly wing shape: from morphology to behaviour

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    International audienceButterflies display extreme variation in wing shape associated with tremendous ecological diversity. Disentangling the role of neutral versus adaptive processes in wing shape diversification remains a challenge for evolutionary biologists. Ascertaining how natural selection influences wing shape evolution requires both functional studies linking morphology to flight performance, and ecological investigations linking performance in the wild with fitness. However, direct links between morphological variation and fitness have rarely been established. The functional morphology of butterfly flight has been investigated but selective forces acting on flight behaviour and associated wing shape have received less attention. Here, we attempt to estimate the ecological relevance of morpho-functional links established through biomechanical studies in order to understand the evolution of butterfly wing morphology. We survey the evidence for natural and sexual selection driving wing shape evolution in butterflies, and discuss how our functional knowledge may allow identification of the selective forces involved, at both the macro-and micro-evolutionary scales. Our review shows that although correlations between wing shape variation and ecological factors have been established at the macro-evolutionary level, the underlying selective pressures often remain unclear. We identify the need to investigate flight behaviour in relevant ecological contexts to detect variation in fitness-related traits. Identifying the selective regime then should guide experimental studies towards the relevant estimates of flight performance. Habitat, predators and sex-specific behaviours are likely to be major selective forces acting on wing shape evolution in butterflies. Some striking cases of morphological divergence driven by contrasting ecology involve both wing and body morphology, indicating that their interactions should be included in future studies investigating co-evolution between morphology and flight behaviour

    Laboratory studies examining aspects of scent marking, traplining and remote detection of reward in the foraging bumblebee.

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    PhDEnergy from food is essential for the survival of all animals. For decades, bumblebees have been used as model organisms for studying animal foraging strategies. Here, I use bumblebees to examine two foraging strategies: scent marking and traplining. I find that experience and long term memory play an important role in both of these strategies. I show that bees interpret scent marks differently depending on context. They learn to rely on these scent marks to different degrees depending on flower handling time. Bees also learn to associate the same scent marks with high and low rewarding food, which means the same scent promotes and suppresses acceptance of flowers. Contrary to previous speculation, I find that these scent marks are not pheromonal signals specifically evolved to play a role in foraging. Rather they are incidental cues that bees learn to use to improve foraging performance and locate their nesting sites. Experience is also important in developing repeatable stable routes between food sites i. e. traplines. I show that bees required long term spatial memory to gradually form traplines. They reduced their travel distance by linking near neighbour flowers, which did not result in using the shortest routes. Traplining bees were also less likely to revisit emptied flowers and spent less time searching for these flowers. For decades, scientists have used water to control for remote effects of sucrose solution in experiments. I find that bees are able to detect the difference between these two liquids without contact chemoreception. The exact cue they use remains to be determined, but it is not humidity.University of London Central Research fun

    Trophic niche shifts and phenotypic trait evolution are largely decoupled in Australasian parrots

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    Background: Trophic shifts from one dietary niche to another have played major roles in reshaping the evolutionary trajectories of a wide range of vertebrate groups, yet their consequences for morphological disparity and species diversity differ among groups. Methods: Here, we use phylogenetic comparative methods to examine whether the evolution of nectarivory and other trophic shifts have driven predictable evolutionary pathways in Australasian psittaculid parrots in terms of ecological traits such as body size, beak shape, and dispersal capacity. Results: We found no evidence for an ‘early-burst’ scenario of lineage or morphological diversification. The bestfitting models indicate that trait evolution in this group is characterized by abrupt phenotypic shifts (evolutionary jumps), with no sign of multiple phenotypic optima correlating with different trophic strategies. Thus, our results point to the existence of weak directional selection and suggest that lineages may be evolving randomly or slowly toward adaptive peaks they have not yet reached. Conclusions: This study adds to a growing body of evidence indicating that the relationship between avian morphology and feeding ecology may be more complex than usually assumed and highlights the importance of adding more flexible models to the macroevolutionary toolbox.info:eu-repo/semantics/publishedVersio

    Behavioral responses of Brazilian free-tailed bats (\u3ci\u3eTadarida brasiliensis\u3c/i\u3e) to noctuid moth migrations

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    Animal migrations involve significant movement of biomass across landscapes and are likely to have cascading effects on animal and plant communities. However, most studies on migration address the behavior and ecology of single taxa, such as birds or insects. Few consider more than one trophic level or predator/prey interaction within the overall migration context. I studied the migration ecology of noctuid moths and of Brazilian free-tailed bats in Texas. Noctuid moth migrations during the 2010-2012 fall seasons were driven significantly by weather at the regional and local levels. Bats also responded to the same weather patterns, with changes in body mass and bat flight activity linked to increased northerly wind after cold front passage. Many of the behavioral and physiological changes in bats were more likely due to their own migratory cycles, rather than in direct response to the local availability of migratory moths in the study area. Noctuid moths are destructive agricultural pests affecting crops on a continental scale, and the bats offer significant pest control ecosystem services. Since the system is driven by weather, understanding the system is important because it is likely to be affected by climate change

    Camouflage in predators

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    Camouflage – adaptations that prevent detection and/or recognition – is a key example of evolution by natural selection, making it a primary focus in evolutionary ecology and animal behaviour. Most work has focused on camouflage as an anti‐predator adaptation. However, predators also display specific colours, patterns and behaviours that reduce visual detection or recognition to facilitate predation. To date, very little attention has been given to predatory camouflage strategies. Although many of the same principles of camouflage studied in prey translate to predators, differences between the two groups (in motility, relative size, and control over the time and place of predation attempts) may alter selection pressures for certain visual and behavioural traits. This makes many predatory camouflage techniques unique and rarely documented. Recently, new technologies have emerged that provide a greater opportunity to carry out research on natural predator–prey interactions. Here we review work on the camouflage strategies used by pursuit and ambush predators to evade detection and recognition by prey, as well as looking at how work on prey camouflage can be applied to predators in order to understand how and why specific predatory camouflage strategies may have evolved. We highlight that a shift is needed in camouflage research focus, as this field has comparatively neglected camouflage in predators, and offer suggestions for future work that would help to improve our understanding of camouflage.Publisher PDFPeer reviewe

    Carbohydrate Composition and Structure Changes as Phloem Sap is Converted to Nectar in Borago officinalis L. and Select Brassica spp. L.

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    Nectar is a carbohydrate-rich solution produced by nectary organs as a reward to pollinators and animal mutualists. Nectar production involves the upload of carbohydrate (i.e., sucrose) from the phloem sap, intracellular (symplastic) and/or intercellular (apoplastic) transport of carbohydrates into the nectary, and secretion of carbohydrates to the nectary exterior as nectar. To investigate carbohydrate composition and structure changes during nectar production, the carbohydrate composition of phloem sap, nectary fluid, and nectar of Borago officinalis L. and two Brassica spp. L. (Brassica napus L. var. AC Excel, B. napus L. transgenic var. AV 225 R. R., and B. rapa L. var. AC Parkland) were determined employing high performance anion exchange-pulsed amperometric detection (HPAE-PAD) and capillary gas chromatography-flame ionization detection (CGC-FID) chromatographic methods. To elucidate the mechanism(s) of carbohydrate transformation during nectar production, substrate hydrolysis experiments were conducted on both nectaries and nectar, and nectary proteomics analysis was also employed. Carbohydrate composition results showed that: a) sucrose (S; >95% w:v) was present in the phloem sap of both genera; b) fructose (F; >50%), glucose (G; ~45%), and non-sucrose oligosaccharides were present in the nectary fluids of B. officinalis and Brassica spp., indicating that sucrose hydrolysis and carbohydrate synthesis occurred; c) F, G, S, and non-sucrose oligosaccharides were detected in the nectars of both genera with significant concentration differences; d) B. officinalis nectar was sucrose-dominant (S; 61%), whereas Brassica spp. nectars were hexose-dominant (average, F + G; 99%) indicating that sucrose was resynthesized in B. officinalis; and e) common non-sucrose oligosaccharides were detected in B. officinalis and Brassica spp. nectars and unique non-sucrose oligosaccharides were detected in both genera. The observed hydrolysis of sucrose and the synthesis of non-sucrose oligosaccharides in the nectaries and nectars of B. officinalis and Brassica spp. can be explained by the presence of carbohydrases (α-glucosidase, β-fructosidase β-glucosidase) and synthases (sucrose synthase, sucrose phosphate synthase) as confirmed by select substrate and proteomics experiments. The significant difference in the sucrose concentration of the floral nectar of B. officinalis is attributed to sucrose phosphate synthase activity in B. officinalis when compared to Brassica spp., and by the type of carbohydrate transport pathway (symplast vs apoplast) followed

    Insects

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    In this thematic series, engineers and scientists come together to address two interesting interdisciplinary questions in functional morphology and biomechanics: How do the structure and material determine the function of insect body parts? How can insects inspire engineering innovations

    Bats, insects and pecans: habitat use and ecosystem services of insectivorous bats in a pecan agroecosystem in central Texas

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    Comprehensive wildlife conservation strategies must include consideration of the agricultural matrix and its integration into the greater landscape. Bats are postulated to provide critical pest suppression services, but the effects of agricultural intensification on insectivorous bats are not clear. Few studies have thoroughly investigated the ecosystem services provided by bats due, in part, to limited understanding of species-specific habitat use in agricultural landscapes, difficulties in prey identification, and the challenge of quantifying the impact of bats on pest populations and crops. My dissertation integrates these components to describe ecological relationships between the insects and bats associated with a pecan agroecosystem in central Texas. Specifically, I focus on the predator-prey relationship between bats and the pecan nut casebearer moth (PNC), a devastating pest of pecans. I begin with a literature review of the ecosystem services of insectivorous bats and the data necessary to thoroughly evaluate these services. I then assess the potential factors influencing species composition and spatio-temporal distributions of bats within the pecan agroecosystem. My results demonstrate higher activity and diversity of bats within the pecan agroecosystem than in the surrounding landscape likely due to roosting opportunities, but species-specific and seasonal differences exist in the effects of management intensity. Next, I investigate direct interactions between bats and PNC by measuring prey consumption patterns. I found that five species of bats prey upon PNC moths during all three critical population peaks prior to insecticide application, but there is variability in consumption among species. Finally, I assess indirect interactions between bats and pecans, by evaluating the effect of bat predation risk on pecan damage by PNC larvae. A negative relationship between foraging activity by bats and both PNC moths and PNC larval damage to pecans provides evidence that bat predation has quantitative downstream effects. My results highlight the conservation value of the agricultural matrix for bats and the complexities of accurately documenting ecosystem services provided by free-ranging mobile organisms
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