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  • 1
    Electronic Resource
    Electronic Resource
    Three conditions for the evolution of eusociality: Are they sufficient? (1994)
    Springer
    Insectes sociaux 41 (1994), S. 395-400 
    Details
    ISSN: 1420-9098
    Keywords: Eusociality ; habitat ; defense ; ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary I hypothesize that three conditions, (1) food-shelter coincidence, (2) strong selection for defense, and (3) ability to defend, are sufficient, although not necessary, for the evolution of eusociality in group-living animals. Reasons for this association between ecology and eusociality include extremely high value of the habitat, possibilities for habitat inheritance, high relatedness in claustral situations, self-sufficiency of juveniles, greater ability of workers to reproduce, and trade-offs between defensive ability and dispersal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01240642
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A memory-based approach to navigation (1993)
    Springer
    Biological cybernetics 69 (1993), S. 385-393 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A memory-based system for autonomous indoor navigation is presented. The system was implemented as a follow-midline reflex on a robot that moves along the corridors of our institute. The robot estimates its position in the environment by comparing the visual input with images contained in its memory. Spatial positions are represented by classes. Memories are formed during a learning phase by encoding labeled images. The output of the system is the a posteriori probability distribution of the classes, given an input image. During performance, an image is assigned to the class that maximizes the probability. This work shows that extensive use of memory can reduce information processing to a simple and flexible procedure, without the need of complicated and specific preprocessing. The system is shown to be reliable, with good generalization capability. With learning limited to a small part of a corridor, the robot navigates along the entire corridor. Furthermore, it is able to move in other corridors of different shape, with different illumination conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01185410
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A memory-based approach to navigation (1993)
    Springer
    Biological cybernetics 69 (1993), S. 385-393 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A memory-based system for autonomous indoor navigation is presented. The system was implemented as a follow-midline reflex on a robot that moves along the corridors of our institute. The robot estimates its position in the environment by comparing the visual input with images contained in its memory. Spatial positions are represented by classes. Memories are formed during a learning phase by encoding labeled images. The output of the system is the a posteriori probability distribution of the classes, given an input image. During performance, an image is assigned to the class that maximizes the probability. This work shows that extensive use of memory can reduce information processing to a simple and flexible procedure, without the need of complicated and specific preprocessing. The system is shown to be reliable, with good generalization capability. With learning limited to a small part of a corridor, the robot navigates along the entire corridor. Furthermore, it is able to move in other corridors of different shape, with different illumination conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199438
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Performance of phase-based algorithms for disparity estimation (1997)
    Springer
    Machine vision and applications 9 (1997), S. 334-340 
    Details
    ISSN: 1432-1769
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. Stereoscopic depth analysis by means of disparity estimation has been a classical topic of computer vision, from the biological models of stereopsis [1] to the widely used techniques based on correlation or sum of squared differences [2]. Most of the recent work on this topic has been devoted to the phase-based techniques, developed because of their superior performance and better theoretical grounding [3, 4]. In this article we characterize the performance of phase-based disparity estimators, giving quantitative measures of their precision and their limits, and how changes in contrast, imbalance, and noise in the two stereo images modify the attainable accuracy. We find that the theoretical range of measurable disparities, one period of the modulation of the filter, is not attainable: the actual range is approx. two-thirds of this value. We show that the phase-based disparity estimators are robust to changes in contrast of 100% or more and well tolerate imbalances of luminosity of 400% between the images composing the stereo pair. Clearing the Gabor filter of its DC component has been often advocated as a means to improve the accuracy of the results. We give a quantitative measure of this improvement and show that using a DC-free Gabor filter leads to disparity estimators nearly insensitive to contrast and imbalance. Our tests show that the most critical source of error is noise: the error increases linearly with the increase in noise level. We conclude by studying the influence of the spectra and the luminosity of the input images on the error surface, for both artificial and natural images, showing that the spectral structure of the images has little influence on the results, changing only the form of the error surface near the limits of the detectable disparity range. In conclusion, this study allows estimation of the expected accuracy of custom-designed phase-based stereo analyzers for a combination of the most common error sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001380050052
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  • 5
    Electronic Resource
    Electronic Resource
    Real-time parallel computation of disparity and optical flow using phase difference (1996)
    Springer
    Machine vision and applications 9 (1996), S. 87-96 
    Details
    ISSN: 1432-1769
    Keywords: Phase-based image matching ; Disparity ; Optical flow ; Parallel processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A phase-difference-based algorithm for disparity and optical flow estimation is implemented on a TI-C40-based parallel DSP system. The module performs real-time computation of disparity maps on images of size 128 × 128 pixels and computation of optical flows on images of size 64 × 64 pixels. This paper describes the algorithm and its parallel implementation. Processing times required for the computation of disparity maps and velocity fields and measures of the algorithm's performance are reported in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01216814
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  • 6
    Electronic Resource
    Electronic Resource
    Real-time parallel computation of disparity and optical flow using phase difference (1996)
    Springer
    Machine vision and applications 9 (1996), S. 87-96 
    Details
    ISSN: 1432-1769
    Keywords: Key words:Phase-based image matching – Disparity – Optical flow – Parallel processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. A phase-difference-based algorithm for disparity and optical flow estimation is implemented on a TI-C40-based parallel DSP system. The module performs real-time computation of disparity maps on images of size $128 \times 128$ pixels and computation of optical flows on images of size $64 \times 64$ pixels. This paper describes the algorithm and its parallel implementation. Processing times required for the computation of disparity maps and velocity fields and measures of the algorithm's performance are reported in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001380050031
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Synergism between sib-rearing and sex ratio in Hymenoptera (1989)
    Springer
    Behavioral ecology and sociobiology 24 (1989), S. 155-162 
    Details
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In many bees and wasps, solitary females produce offspring without help from other females. The transition from lone mothers producing offspring to situations in which females often help to rear siblings is an important step in the origins of complex sociality and nonreproductive castes. Recent work on Hymenoptera has stressed the role of sex ratio variation in this transition; when a mother's brood is more female biased than average, older daughters are favored to help rear their younger siblings because they are more closely related to sisters than to their own offspring. Here the direction of causality is from biased sex ratios, which arise by some extrinsic mechanism, to the origins of sib-rearing (eusociality). We present a model in which there is a synergism between sib-rearing and female-biased sex ratios, which may either complement the sex ratio variation idea by increasing the rate at which helping spreads or be an alternative hypothesis about the origins of eusociality. The synergism in our model depends on three conditions. 1) Daughters that help cause more food to be provisioned per offspring, which in turn causes larger offspring. 2) Females gain more than males by being large, which favors mothers with helpers to produce a higher proportion of daughters. 3) A helper's inclusive fitness rises as her mother's brood becomes increasingly female biased because a female helper is more closely related to her sisters than to her brothers. A female helper may also be more closely related to her sisters than to her own offspring, but this particular sibling-offspring relatedness asymmetry is not required by the synergism model. These three conditions create a synergism which favors a rapid transition from solitary (subsocial) to eusocial. Demographic and ecological factors that facilitate the evolution of eusociality reduce the stringency of the relatedness asymmetry condition (3) required by our idea. The synergism model therefore complements factors other than relatedness that may have been important during the evolution of eusociality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292098
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  • 8
    Electronic Resource
    Electronic Resource
    Adaptation, compromise, and constraint: the development, morphometrics, and behavioral basis of a fighter-flier polymorphism in male Hoplothrips karnyi (Insecta: Thysanoptera) (1988)
    Springer
    Behavioral ecology and sociobiology 23 (1988), S. 93-104 
    Details
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Males of the colonial, wing-polymorphic thrips Hoplothrips karnyi (Hood) fight each other with their forelegs in defense of communal female oviposition areas. In this study, males were reared individually under varying conditions of food deprivation to investigate the developmental cues used in morph determination and the relationships between wing morph, developmental time in each instar, propupal weight, and five adult morphological characters associated with fighting ability and dispersal ability. Males deprived of food for five days midway through the second (final) larval instar had smaller propupal weights and were more likely to develop wings than males deprived of food in the first instar or control males. However, the mean propupal weight of all males that developed wings was not significantly less than that of wingless males. Wing morph of female parents had no measurable effect on this character in the offspring. Wingless males possess relatively larger fore-femora and prothoraces than do winged males, but winged males possess relatively larger pterothoraces (Fig. 1). Behavioral observations of wingless and winged males of similar weight as propupae showed that wingless males won fights and became dominant in oviposition areas. Thus, a trade-off exists between characters associated with male fighting and dispersal ability. The cost of wings, in terms of fore-femora size and prothorax size, increased with propupal weight. Wingless males that developed in the experimental treatment that produced a high proportion of winged males were relatively small in size, and were intermediate in body shape with respect to winged males and other wingless males (Fig. 2). This shape intermediacy indicates that there may be developmental constraints on alternative tactics of resource allocation. Total developmental time varied between wing morphs, but was not correlated with propupal weight or adult morphological characters of winged or wingless males. For wingless males that developed in the treatment that produced a high proportion of winged males, adult morphological characters were negatively correlated with the duration of the second instar. This correlation suggests that the development of small wingless males involves a compromise between the benefits of large adult size and the costs of prolonging the second instar to increase the probability of becoming larger.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00299892
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  • 9
    Electronic Resource
    Electronic Resource
    Aggregation Pheromones of Two Geographical Isolates of the New Guinea Sugarcane Weevil, Rhabdoscelus obscurus (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 2763-2780 
    Details
    ISSN: 1573-1561
    Keywords: Aggregation pheromones ; Coleoptera ; Curculionidae ; cytochrome oxidase I ; 2-methyl-4-heptanol ; (E2)-6-methyl-2-hepten-4-ol ; 2-methyl-4octanol ; mitochondrial DNA ; New Guinea sugarcane weevil ; palm weevil ; Rhabdoscelus obscurus ; rhynchophorol ; sibling species ; sugarcane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The aggregation pheromones were studied from two geographical isolates (Hakalau, Hawaii, and Silkwood, Queensland, Australia) of the New Guinea sugarcane weevil, Rhabdoscelus obscurus. Coupled gas chromatographic–electroantennographic detection (GC-EAD) and GC–mass spectrometric (MS) analyses of Porapak Q volatile extract from male and from female Hawaiian R. obscurus revealed a single EAD-active, male-specific candidate pheromone, which was identified as 2-methyl-4-octanol (1). Corresponding volatile analyses from male and from female Australian R. obscurus consistently revealed three EAD-active, male-specific candidate pheromone components that were identified as 1, (E2)-6-methyl-2-hepten-4-ol (rhynchophorol) (2), and 2-methyl-4-heptanol (3). In field experiment 1 in Hakalau, Hawaii, traps baited with a stereoisomeric mixture of synthetic 1 (3 mg/day) plus sugarcane captured more weevils than did traps baited with 1 or sugarcane alone or no bait, indicating that 1 is the pheromone of the Hawaiian R. obscurus population. In field experiment 2, conducted in Silkwood, Australia, traps baited with stereoisomeric mixtures of synthetic 1, 2, and 3 (3 mg/day each) plus sugarcane caught more weevils than did unbaited traps or traps baited with 1, 2, and 3 or sugarcane. Testing candidate pheromone components 1, 2, and 3 in experiments 2–5 in all possible binary, ternary, and quaternary combinations with sugarcane, indicated that 1 and 2 in combination, but not singly, are pheromone components of the Australian R. obscurus population. Weevils from several locations in Australia and Hawaii could not be differentiated using traditional morphological characters or ultrastructural comparisons with scanning electron microscopy (SEM). However, comparisons of mtDNA sequences (cytochrome oxidase I; regions I1 to M4; 201 base pairs) revealed 5.5% variation between the Hawaiian (N = 2) and the Australian (N = 4) samples. There was no intrapopulation variation in sequence data from the weevils from Hawaii versus Australia, suggesting that they are sibling species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026437809875
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    Paper (German National Licenses)
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