Thesis - University of Michigan. / Reprinted from the American naturalist, vol. LXXX, no. 794 ... September-October, 1946. Literature cited: p. 546.

Thesis (Ph. D.)--University of California. / Cover title. "Sonderabdruck aus dem Archiv für Entwicklungsmechanik der Organismen. XXXI. Bd., 1. Heft." Added t.p.: Berkeley, California, 1910. "Literature": p. 161-162.

The Red Queen hypothesis posits that, despite its costs, sexual reproduction is ubiquitous because it yields genotypic variation that can be adaptive in spatially or temporally heterogenous environments. Despite this, some metazoan species engage in facultative and even obligate cloning; investigation of these species can shed light on the conditions in which cloning might be an adaptive strategy. Freshwater snails are excellent study species for exploration of these questions due to their variable reproductive modes, relative ease of collection, and low vagility, leading to the ability to gather genetically distinct groups within a small geographic area. Campeloma decisum is a North American freshwater snail comprising both sexual populations, containing males and females, and parthenogenetic populations, containing only females. These two reproductive modes have been observed to be geographically grouped, with the parthenogens found in northern, formerly glaciated regions, and the sexuals living further south. The goal of this study was to obtain representatives from both sexual and parthenogenetic populations and perform phylogenetic analyses to gain insight into the origin of parthenogenesis within this group and elucidate any cryptic genetic diversity. Eleven populations of C. decisum were sampled and 46 cox1 sequences were obtained from them. These data were combined with Campeloma cox1 sequences from GenBank and maximum-likelihood trees were obtained using IQ-TREE. The resulting trees supported distinct sexual and parthenogenetic clusters, separated by relatively long internal branches. However, the outgroup branch was long, and SOWH tests 1) suggest that the position of the root of Campeloma cannot be determined with these data and 2) reject a clade comprising all C. decisum sequences. C. decisum harbors cryptic genetic diversity to the extent that it seems to comprise at least two genetically distinct lineages.

No description available.

Menetia greyii, a small Australian skink, has recently been determined to be a species complex that consists of both sexual and parthenogenetic taxa (Adams et al. 2003). In total, seven distinct taxa have been identified in the south-central region of Australia. This includes three sexual taxa, three apparent parthenogen lineages, and one lizard of uncertain status The study population occurs near Bundey Bore station in the semi-arid region of South Australia (approximately 160km north east of Adelaide). At this site, one sexual taxon (SAS) and two all-female parthenogenetic taxa (WP and RP3) were found to occur in sympatry. In a search for ecological differences, I examined spatial, thermal, physiological and morphological niche relationships in the parthenogenetic and sexual forms. Capture rates were used to determine microhabitat and macrohabitat use in the field. The use of different microhabitats and the amount of time spent occupying different exposures (sun vs. shade) were also examined under laboratory conditions. Thermal preferences, physiological performance (sprint speed ability) and daily activity periods were investigated in the laboratory. The study failed to find any major differences among the different taxa that would indicate they are partitioning resources and therefore explain how the sexual and parthenogenetic forms are coexisting. The only difference observed was that the parthenogens expressed superior sprinting ability, running faster than the sexuals over a range of temperatures. In addition, I found that sexual and parthenogenetic females within this population differed very little in their reproductive effort and output, indicating that RP3 and WP parthenogens possess a reproductive advantage over sexual females as a result of not having to produce males (Williams 1975, Maynard-Smith 1978, Bell 1982). In staged interactions between pairs of sexual and parthenogen individuals, the parthenogens were more aggressive and dominated the sexuals. As a result, the parthenogens were able to outcompete the sexuals for food items. This had serious consequences on fitness, with the sexuals losing significantly more weight than the parthenogens. All of these factors would suggest that the parthenogens should eliminate the sexuals at Bundey Bore. Despite this, the parthenogenetic females at Bundey Bore do not outnumber the sexual subpopulation. This raises the question of how the sexuals are persisting. An examination of endoparasites in the scats of parthenogen and sexual M. greyii found that WP parthenogens had significantly higher parasite prevalence than sexuals. Further to this, there is evidence of matings occurring within the study population between sexual males and WP parthenogen females with five tetraploid males being captured. Therefore, WP parthenogens may be suffering from destabilising hybridization. These factors may account for why the parthenogens (or at least the WP parthenogens) have not competitively excluded sexual M. greyii from Bundey Bore. Other possible reasons are discussed in the general discussion in Chapter 8.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

This article examines female asexual reproduction, or parthenogenesis, in Hesiod’s Theogony and argues that it is a symptom of the unprecedented and unparalleled female presence Hesiod inserts into his cosmos. This presence in turn reflects Hesiod’s incorporation of gender difference and conflict as indispensable both to the creation and, paradoxically, to the stability of the universe. Five of Hesiod’s deities reproduce parthenogenetically: Chaos, Gaea, Night, Strife, and Hera, of whom all but the sexually indeterminate Chaos are female. Hesiod’s male gods have no analogous reproductive ability. The parthenogenetic phases of the early goddesses form much of the fundamental shape and character of the universe, while in the case of Hera, parthenogenesis serves initially as an act of defiance against Zeus but ultimately enforces his reign. Parthenogenesis does not have these functions in either the Near Eastern or other Greek cosmogonic traditions, a difference that reflects Hesiod’s greater emphasis on female participation in his succession myth. Yet Hesiod’s cosmogonic narrative, like others, culminates in the lasting reign of a male god, Zeus. In this context parthenogenesis is a manifestation of female creation, which ultimately reinforces the stability of a male sovereign. The relative prominence of parthenogenesis in the Theogony reflects Hesiod’s emphasis on gender difference and conflict as indispensable to a cosmos in which conflict and concord coexist as equal partners in creation and stability.

Thesis (Ph. D.)--University of Michigan, 1926. / Caption title. Thesis note in foot-note on p. 301. "Contributions from the Department of Zoölogy, Smith College, no. 138." "Reprinted from Biological bulletin, vol. L., no. 4, April, 1926." "Literature": p. 335-338.

Several parthenogenetic lineages occur within the lizards of the genus Darevskia (Sauria: Lacertidae) which are endemic to southern Transcaucasus. High level of heterozygosity, cause by thein hybrid origin, is one of the crucial aspects of thein evolutionary potential, as well as the asexual reproduction. Heterosis on one side is in the opposition to the outbreeding depression and genetic uniformity of the clones on the other side. Aim of this work is to evaluace if these aspects influence viability of parthenogenetic species and differ them from the sexual ones. We chose the amount of asymmetries as a measure of developmental instability, which we studied on three meristic characters. We also evaluated the pattern of asymmetries in lateral blue spots, which are of signaling importace in lacertid lizards. Our results suggest that there isn't significant difference between parthenogenetic and sexual species in developmental stability, but the sexual ones are more sensitive to population changes. Absence of males may have perhaps the greatest influence on coloration, resulting in loss of symmetry in the blue spots.