Thesis (M.S.)--Missouri University of Science and Technology, 2010. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 28, 2010) Includes bibliographical references (p. 58-62).

Thesis (Ph. D.)--Virginia Commonwealth University, 2010. / Prepared for: Dept. of Human Genetics. Title from title-page of electronic thesis. Includes bibliographical references . Record unavailable until 5/13/2015.

Thèse--Geneva. / "Thèse no. 1250." Bibliography: p. 163-188.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Western Washington University, 2008. / Includes bibliographical references (leaves 64-70) Also available online.

The pallid sturgeon (Scaphirhynchus albus) and shovelnose sturgeon (S. platorynchus) are benthic freshwater fishes that are sympatric throughout the range of the pallid sturgeon. Pallid sturgeon was listed as endangered under the Endangered Species Act in 1990, while shovelnose is common throughout the range. Previous abundance studies estimate the ratio of adult pallid to shovelnose sturgeon to be on the order of 1:82 in the middle Mississippi River, respectively. Despite adult abundances, reproduction and/or recruitment of pallid sturgeon larvae is undocumented in the middle Mississippi River. The current study aims to confirm the presence of pallid sturgeon reproduction and estimate the relative species abundances of larval pallid, shovelnose and hybrid sturgeon in the middle Mississippi River. Since larval pallid, shovelnose and hybrid sturgeon are virtually identical morphologically, the use of DNA markers was required for species designations; sixteen previously developed microsatellite loci were used in this study. Of the 583 larval Scaphirhynchus sturgeon collected from the middle Mississippi River, 581 were shovelnose, one was a hybrid and one was a pallid. This study was the first to genetically confirm the presence of pallid sturgeon reproduction in the middle Mississippi River. Differences in species ratios between adult and larval Scaphirhynchus sturgeon could be explained by three potential hypotheses; life history characteristics accentuate species ratios between adult and larval stages, pallid are experiencing low reproduction and/or low recruitment, or pallid larvae reside in different microhabitat locations compared to shovelnose.

The usefulness of interspecific crosses between Sitka spruce (Picea sitchensis (Bong.) Carr.) and interior spruce (Picea glauca (Moench) Voss, Picea engelmannii Parry and their hybrids) was investigated in one coastal environment. For height growth and bud set most of the variation was at the regional and individual cross level, but very little variation was at the subregional level. The main genetic effects, male and female, accounted for a majority of the genetic variance and additive genetic effects are interpreted as the main factor in the determination of height growth and bud set. For bud set the maternal source of variation accounted for the majority of the genetic variance and a maternal influence on bud set is suggested. Some specific cross combinations were outstanding in height growth and non-additive genetic factors are considered important in these crosses. For bud break most of the variation was due to the residual error, although regions and crosses were statistically significant sources of variation. The Female*Male term was the most important genetic source of variation although bud break is not considered to have as much genetic variation as height and bud set. Large differences were found in the pattern of cold hardiness in the fall and it is considered that photoperiod plays a much larger role than previously thought, especially for interior spruce. Most of the variation was again at the regional and individual cross level. The intermediate performance of the hybrids suggests an inheritance of cold-hardiness based on additive genetic effects. Recommendations are given in the text for the use of these hybrids as well as the areas in which further research would be desireable. / Forestry, Faculty of / Graduate

Intensive field observations were conducted on a small British Columbia coastal stream for two years, supplemented by laboratory rearing and experiment. Stress was placed upon possible isolating mechanisms, as outlined by Mayr, that might serve to keep the marine stickleback (trachurus) and the freshwater form (leiurus)distinct. Lelurus permanently occupies the upper reaches of the stream; trachurus is anadromous, but enters the lower reaches to breed in "pure" freshwater. Between the breeding ground of the two, where some coexistence occurs, hybridization between leiurus and trachurus is extensive, but it is restricted to very narrow zones both in Little Campbell River near Vancouver and in certain Vancouver Island streams. Morphological analysis provides firm circumstantial evidence that hybrids are plentiful and that back-crossing occurs. Hybridization is confirmed by rearing experiments in the laboratory with crosses in all combinations. Most backcrossing is to the freshwater race and this is considered in detail. Behavioural experiments demonstrated the absence of mate preference; random mating occurs with respect to ethological isolation and hybrids perform courtship and parental care activities normally. Rearing hybrids uniformly and in all conbinations demonstrated the absence of genetic incompatibility, and vigorous offspring were produced. Fertile hybrids are abundant in the wild, but the sexes are seasonally isolated from one another. Behavoiral and genetic blocks to hybridization are absent, and thus there is no means to prevent hybridization where leiurus and trachurus come together. But evidence from the field and from preference tests demonstrated that ecological isolating mechanisms are very powerful barriers to hybridization. This is enforced to some extent by partial seasonal isolation, but early spawning migrants make a major contribution to hybridization in the Little Campbell River. Several factors probably operate to cause very narrow hybrid zones in stickle-backs, including a sedentary habit, habitat preference, and hybrid inferiority outside the hybrid zone. The latter could not be detected inside the hybrid zone. The complex of Isolating mechanisms found may well produce stable hybrid zones over long periods of time, and is discussed. Reinforcement of ecological isolating mechanisms probably occurs, and Moore's criticism of the spread of reinforced genotypes would not apply in this instance. Adaptation and consequent ecological isolating mechanisms are the cause of hybrid inferiority. In this instance pre and postmating mechanisms cannot be separated, for they go hand in hand. Geographic speciation is possible but problematical, and sympatric speciation cannot be excluded as a plausible explanation of divergence between sticklebacks as a result of disruptive selection. Distributional patterns of leiurus can best be explained by repeated and independent origins from trachurus. The two forms fulfill the species definition by Mayr and remain reproductively isolated, have well developed isolating mechanisms, and show considerable genetic divergence, much of it polygenic. There is no evidence that, introgression occurs, but a reverse cline in leiurus as well as very narrow hybrid zones demonstrates that selection severely restricts gene flow. Reproductive isolation between marine and freshwater forms seems to be widespread around the hemisphere. / Science, Faculty of / Zoology, Department of / Graduate

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第17831号 / 農博第2016号 / 新制||農||1016(附属図書館) / 学位論文||H25||N4788(農学部図書室) / 30646 / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 中坊 徹次, 准教授 田川 正朋, 准教授 豊原 治彦 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Agropyron trachycaulum (Link) Malte and Agropyron spicatum Pursh, both native range grasses of the Great Basin, often hybridize in nature. A. trachycaulum, is a tetraploid with 28 chromosomes. It has awnless or awntipped lemmas and small anthers. A. spicatum is a diplois with 14 chromosomes. It is characterized by having long awn that bend at maturity, and anthers which are about four times longer than A. trachycaulum. Artificial hybrids are intermediate between parents in awn and anther lengths and have 21 chromosomes. A natural population in Utah was found consisting of A. trachycaulum, A. spicatum, plants resembling the artificial hybrids, and intermediates exhibiting the whole spectrum of variation between the two parents. Regardless of the morphological variation expressed by the natural population only three levels of chromosome numbers are found. Plants have either 14, 21, or 28 chromosomes. This means that only gametes on the seven or fourteen chromosome levels are functional. Only five seeds from 28,870 florets were harvested from the natural hybrids from Thistle Flat. Since these natural hybrids are highly sterile, interbreeding among the hybrids is probably rare. Because progeny from 21-chromosome plants have only 14 chromosomes, A. spicatum was probably the male parent. The variable morphology of A. trachycaulum accompanied by reduced pollen and seed fertility suggests that it has been introgressed with A. spicatum characters. Therefore, both cytological and morophological evidence indicates reciprocal introgression between A. trachycaulum and A. spicatum. Even though A. trachycaulum and A. spicatum have different levels of chromosome numbers, this is not a strong enough genetic barrier to prevent genes to flow between them. Because of introgression considerable variation can be maintained which may be of considerable evolutionary importance to both species.