A three-parameter developmental model for analyzing fluctuating asymmetry in meristic characters.
Item
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Title
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A three-parameter developmental model for analyzing fluctuating asymmetry in meristic characters.
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Identifier
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AAI9917718
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identifier
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9917718
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Creator
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Young, John Raymond.
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Contributor
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Adviser: Robert Rockwell
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Date
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1999
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Biostatistics | Biology, Ecology | Biology, Zoology
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Abstract
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Fluctuating asymmetry has been proposed as a population index of developmental stress resulting from pollution, extreme genetic homozygosity or heterozygosity, or environmental conditions. However, in many instances, measures of fluctuating asymmetry in meristic characters have been inconsistent in distinguishing among populations exposed to different levels of contaminants or with different amounts of genetic variation. An alternate measure of fluctuating asymmetry, s&d4;a , is derived from a three-parameter model of the developmental process. A numerical search algorithm is used to find maximum likelihood estimates of the model parameters m,sL , and sa .; s&d4;a is less sensitive to bias from variation in the mean character value than are indices based on the difference between right and left counts. Likelihood ratio tests for s&d4;a exhibit nominal levels of alpha-error, and yet are as or more powerful than tests for the alternative measures.;Data from five studies of fluctuating asymmetry in fish were reanalyzed using s&d4;a and compared to the analyses originally reported. Overall, use of the three-parameter model did not change the conclusions of the original investigators. The failure to find strong relationships of heterozygosity and pH with fluctuating asymmetry could be due to a truly weak relationship, or to other factors such as low sample sizes, errors in character counts, or use of mixed-age samples.;Fluctuating asymmetry of pectoral fin rays was also examined in anadromous striped bass collected in from the Roanoke River, Chesapeake Bay, and Hudson River in 1974--1975 and 1989. Fluctuating asymmetry was estimated by s&d4;a and three additional measures. Tests based on s&d4;a indicated significant differences among the three stocks, and between the two data sets for each of the three stocks. Tests based on the other three asymmetry indices were not as powerful at detecting these differences.;When the data were segregated by year class and subjected to a nested ANOVA, year-within-stock-and-river was the only variance component that exceeded the magnitude of the error component, indicating that year-to-year variation in fluctuating asymmetry is large for these populations and could obscure any differences due to stock, or river within stock.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
