Donald S. Burdick

VARIATION IN THE DEFENSE STRATEGIES OF PLANTS: ARE RESISTANCE AND TOLERANCE MUTUALLY EXCLUSIVE?

Plants can employ two general strategies to defend themselves against herbivory: they can either reduce the amount of damage they experience (resistance), or they can tolerate herbivore damage. Theoretical considerations suggest that, in many cases, tolerance and resistance are redundant strategies, and may therefore be mutually exclusive adaptations. In this investigation of natural populations of the annual plant Arabidopsis thaliana we examine whether the pattern of selection acting on resistance and tolerance favors the evolution of one defense strategy, or the other, but not both. We found that the joint pattern of selection acting on tolerance and two resistance traits, trichome density and total glucosinolate concentration, indicated that there were not alternate peaks in the fitness landscape favoring either resistance or tolerance. Rather, selection favored the retention of both tolerance and resistance. One reason for the absence of mutually exclusive alternative resistance/tolerance strategies is the absence of a negative genetic correlation between resistance and tolerance. An unexpected result is the detection of disruptive selection acting on tolerance, which seems to result from a nonlinear relationship between tolerance and its costs.

Testing for Environmentally Induced Bias in Phenotypic Estimates of Natural Selection: Theory and Practice

Measuring natural selection has been a fundamental goal of evolutionary biology for more than a century, and techniques developed in the last 20 yr have provided relatively simple means for biologists to do so. Many of these techniques, however, share a common limitation: when applied to phenotypic data, environmentally induced covariances between traits and fitness can lead to biased estimates of selection and misleading predictions about evolutionary change. Utilizing estimates of breeding values instead of phenotypic data with these methods can eliminate environmentally induced bias, although this approach is more difficult to implement. Despite this potential limitation to phenotypic methods and the availability of a potential solution, little empirical evidence exists on the extent of environmentally induced bias in phenotypic estimates of selection. In this article, we present a method for detecting bias in phenotypic estimates of selection and demonstrate its use with three independent data sets. Nearly 25% of the phenotypic selection gradients estimated from our data are biased by environmental covariances. We find that bias caused by environmental covariances appears mainly to affect quantitative estimates of the strength of selection based on phenotypic data and that the magnitude of these biases is large. As our estimates of selection are based on data from spatially replicated field experiments, we suggest that our findings on the prevalence of bias caused by environmental covariances are likely to be conservative.

An introduction to tensor products with applications to multiway data analysis

Abstract The concepts of tensor algebra and vector space geometry provide a unifying framework for multilinear data analysis which simplifies notation and leads to economy of thought. Avoiding too much abstraction too soon in defining tensor products makes these concepts accessible. Examples are given of the use of tensor algebra in the analysis of bilinear and trilinear models arising in fluorescence spectroscopy.

Computer Simulation Experiments with Economic Systems: The Problem of Experimental Design

Abstract Experimental design considerations have been virtually ignored by economists who have conducted computer simulation experiments with models of economic systems. The objective of this paper is to spell out in detail the relationship between existing experimental design techniques and techniques of data analysis and the design of simulation experiments with economic systems. We begin by defining the problem of experimental design as applied to computer simulation experiments. With the aid of an example model, we explore several techniques of data analysis and a number of specific experimental design problems. Although this paper is oriented towards the design of computer simulation experiments in economics, the techniques which are discussed are of a general nature and should be applicable to the design of simulation experiments in other disciplines.

The Use of Nearest Neighbor Frequency Analyses in Studies of Association

Baker, H. G., P. A. Opler, and 1. Baker. 1978. A comparison of the amino acid complements of floral and extrafloral nectar. Botanical Gazette 139:322-332. Faegri, K., and Van der PijI, L. 1966. The principles of pollination ecology. Pergamon, Oxford, England. Feinsinger, P., and L. A. Swarm. 1978. How common are ant-repellent nectars? Biotropica 10:238-239. Gerner, W. 1972. Bluteneinbruch durch Apiden. Zoologische Anzeiger 189:34-44. Ingels, J. 1976. Observations on the hummingbirds Orthorhynchus cristatus and Eulampis jugularis of Martinique (West Indies). Gerfaut 66:129-132. Inouye, D. W. 1981, in press. The ecology of nectar robbing. In B. L. Bentley and T. S. Elias, editors. The biology of nectaries. Columbia University Press, New York, New York, USA. Koeman-Kwak, M. 1973. The pollination of Pedicularis palustris by nectar thieves (short-tongued bumblebees). Acta Botanica Neerlandica 22:608-615. McDade, L. A., and S. Kinsman. 1980, in press. The impact of floral parasitism in two neotropical hummingbirdpollinated plant species. Evolution. Rust, R. W. 1979. Pollination of Impatiens capensis: pollinators and nectar robbers. Journal of the Kansas Entomological Society 52:297-308. Schremmer, F. 1972. Der Stechsaugrussel, der Nektarraub, das Pollensammeln und der Blutenbesuch der Holzbienen (Xylocopa) (Hymenoptera, Apidae). Zeitschrift fur Morphologie der Tiere 72:263-294.

Design of computer simulation experiments for industrial systems

Computer simulation experiments design for industrial systems, considering variance techniques, multiple ranking procedures, sequential sampling and spectral analysis

Estimating the 95% effective defibrillation dose

Minimum-squared-error (MinSE) testing protocols and a MinSE estimator that accurately estimate the voltage that defibrillates 95% of the time (the ED95) are presented. The MinSE experimental procedures, presented in the form of lookup tables, detail the response to successful and unsuccessful trials. The lookup tables also show the ED95 estimates calculated from the observed results using the MinSE estimator. The MinSE estimator and experimental procedure were evaluated in a study of five dogs (19-25 kg, heart weights 139.3-236.9 gm) using nonthoracotomy implantable defibrillator electrodes and a biphasic defibrillation waveform (3.5 ms first phase, 2.0 ms second phase). For ED95 between 0.0 and 800.0 V, the measured RMS error was 15% of the mean measured ED95 for the MinSE, four-test-shock, ED95 estimates. If the protocols are designed with an ED95 population distribution assumption for animals of the same species and size, and defibrillation is constrained to one electrode configuration and waveform, the estimates improve by 3.8%. The MinSE approach can be extended to a variety of defibrillation parameter estimation problems.<<ETX>>

An empirical comparison of resolution methods for three-way arrays

Abstract In chemometrics applications it is common to resolve a trilinear array by solving a generalized eigenvalue problem, rather than by employing the iterative PARAFAC algorithm commonly used by psychometricians. Although an eigenanalysis-based procedure works perfectly in the absence of noise, it is not guaranteed to yield least squares resolutions when noise is present. The PARAFAC algorithm on the other hand is guaranteed to reduce the residual sum of squares at each iteration. In this paper we propose synthesizing the two methods by using the resolution generated by eigenanalysis as starting values for the iterative PARAFAC algorithm. We find for simulated four-component data at moderate noise levels that following an eigenanalysis resolution with PARAFAC frequently leads to significant improvement in the quality of the resolution.

Methacholine-induced cutaneous flare response: bivariate analysis of responsiveness and sensitivity

Cutaneous reactions to allergens exhibit a sigmoid dose-response relationship. Available methods for evaluating the allergen skin-test response do not adequately account for the sigmoid curve. Methodologic factors handicap quantitative studies of allergens based on skin-test reactivity. This problem was evaluated with a pharmacologic agonist that mimics cutaneous reactivity. Epicutaneous tests with appropriate concentrations of methacholine were used to provoke flare responses in 84 healthy subjects. A novel hyperbolic tangent model of the sigmoid dose-response curve was used to estimate responsiveness (R) as the midpoint of the sigmoid curve. Sensitivity (C) was estimated as the agonist concentration yielding a flare response equivalent to R. Estimates of sensitivity were independent of estimates of responsiveness (r=-0.0565, p=0.6642). The geometric mean methacholine sensitivity among health subjects was 287 mM/L, and average methacholine responsiveness was 4.9 mm. The mathematic model used in these studies fitted observations surprisingly well (X2(84)=37.044, p greater than 0.95). Differences in methacholine sensitivity and responsiveness related to race, sex, and allergic and/or vasomotor tendencies were detected but were subtle and did not account for a significant portion of the variation among healthy subjects. This model may provide a useful method for quantifying cutaneous immediate hypersensitivity reactions in patients.

The application of sequential sampling to simulation: an example inventory model

Four different sequential sampling procedures are applied to the analysis of data generated by a computer simulation experiment with a multi-item inventory model. For each procedure the cost of computer time required to achieve given levels of statistical precision is calculated. Also the cost of computer time using comparable fixed sample size methods is calculated. The computer costs of fixed sample size procedures versus sequential sampling procedures are compared.