Flowering plants possess striking variation in reproductive traits and mating patterns, even among closely related species. In this thesis, I investigate morphological variation, mating and genetic diversity of five taxa of bird-pollinated Babiana (Iridaceae), including two species with specialized bird perches. Field observations in 12 populations demonstrated that sunbirds were the primary pollinators. Babiana ringens exhibited correlated geographic variation in flower and perch size. Controlled field pollinations revealed self-compatibility and low pollen limitation in B. ringens subspecies, and self-incompatibility and chronic pollen limitation in B. hirsuta. Allozyme markers demonstrated moderate to high selfing rates among populations and considerable variation in levels of genetic diversity. In B. ringens there was a positive relation between the geographic and genetic distance of populations. The results of a manipulative field experiment indicated position-dependent herbivory on inflorescences of B. hirsuta and this could play a role in the evolution of specialized bird perches in Babiana.

Male rat copulation is mediated by estrogen-sensitive neurons in the medial preoptic area (MPO) and medial amygdala (MEA); however, the mechanisms through which estradiol (E2) acts are not fully understood. We hypothesized that E2 acts through estrogen receptor α (ERα) in the MPO and MEA to promote male mating behavior. Antisense oligodeoxyneucleotides (AS-ODN) complementary to ERα mRNA were bilaterally infused via minipumps into either brain area to block the synthesis of ERα, which we predicted would reduce mating. Western blot analysis and immunocytochemistry revealed a knockdown of ERα in each brain region; however, compared to saline controls, males receiving AS-ODN to the MPO showed significant reductions in all components of mating, whereas males receiving AS-ODN to the MEA continued to mate normally. These results suggest that E2 acts differently in these brain regions to express sexual behavior and that ERα in the MPO, but not in the MEA, promotes mating.

The bounded-hybrid superiority hypothesis (BHSH) predicts stable hybrid zones are characterized by hybrids having the highest fitness within the zone. The dynamic-equilibrium hypothesis (DEH) predicts hybrids to have the lowest fitness and mating should be strongly assortative in the hybrid zone. I used phenotypic-based hybrid indices (HI) to assess mating patterns, reproductive success, and survival of hybridizing northern flickers (Colaptes auratus) within the hybrid zone at Riske Creek, British Columbia. Contrary to the BHSH, flickers showed significant assortative pairing (P = 0.038) which may result via passive mate choice if yellow and red flickers migrate from allopatric winter ranges. North American band recoveries show red-shafted and yellow-shafted flickers winter on different sides of the Rocky Mountains while red-orange hybrids from Riske Creek winter in the range of red-shafted flickers. Arrival dates of phenotypes did not support the idea that mating patterns are caused passively via different arrival schedules. However, assortative mating patterns did correlate with regional weather patterns along flicker migration routes as well as the North Atlantic Oscillation (NAO) a continental weather pattern that has been shown to influence various aspects of the annual cycle in other birds. If variable weather patterns result in different mating patterns by affecting migration, the geographic location of the northern portion of the zone may be variable due to the migratory behaviour of individuals.<p>There were no differences among yellow, orange and red flickers to win more agonistic contests or have earlier nest initiation dates, larger clutch sizes, greater hatching success, or produce more fledglings. No colour group had a higher likelihood of having a successful compared to a depredated nesting attempt. Aggression was similar between red (N = 21) and yellow flickers (N = 20) during taxidermy model presentations of pure red-shafted and yellow-shafted flickers. Using Akaikes information criterion (AIC) in Program MARK, I determined survival was best modeled as either constant between males and females or varying annually according to weather. Models incorporating HI had less support but suggested that survival is best modeled as a linear relationship where red-shafted flickers have the highest survival. Survival modeled in quadratic relationships found hybrid flickers to have the highest apparent survival estimates in support of the BHSH. Overall there was no support for reduced hybrid fitness, but survival appears to be influenced more by annual variation rather than strictly by an individuals HI. Overall, I failed to find reduced hybrid fitness in support of the DEH but also failed to find increased hybrid fitness as predicted by the BHSH. Annual changes in selection pressure could prevent introgression of hybrid genes throughout the zone if selection favours red-shafted genes in some years and yellow-shafted genes in other years.

Pollinator visitation patterns should affect pollination success and mating patterns in flowering species. In the orchid family, about one third of the species do not provide any reward for their pollinators. Pollination by deceit is typically associated with low fruit set but may increase the chance of cross-pollination since the pollinator should soon leave the individual plant when there is no reward in the flowers. This may be beneficial if self-fertilisation results in inbreeding depression. I studied the mating patterns of one rewarding and one deceptive orchid in two closely related genera by tracking the fate of stained pollinia. I also conducted controlled crosses to estimate inbreeding depression. The results show that the deceptive orchid Dactylorhiza lapponica has lower pollination success, but higher cross-pollination rate (ca. 90%) than the nectariferous orchid Gymnadenia conopsea (ca. 18% cross-pollination). The results further suggest that in G. conopsea, nocturnal visitors mediate higher geitonogamous pollination rate (ca. 100%) than diurnal visitors (ca. 60%). In both study species, fruits produced from cross-pollination were heavier than fruits produced from selfing. Inbreeding depression for fruit mass did not differ significantly between the two species (δ = 0.21 in D. lapponica and δ = 0.29 in G. conopsea). These data support the hypothesis that pollination by deceit can enhance cross-pollination. A literature study including several rewarding and non-rewarding orchid species indicated lower geitonogamy in the deceptive orchids, but the difference was not statistically significant.

The bounded-hybrid superiority hypothesis (BHSH) predicts stable hybrid zones are characterized by hybrids having the highest fitness within the zone. The dynamic-equilibrium hypothesis (DEH) predicts hybrids to have the lowest fitness and mating should be strongly assortative in the hybrid zone. I used phenotypic-based hybrid indices (HI) to assess mating patterns, reproductive success, and survival of hybridizing northern flickers (Colaptes auratus) within the hybrid zone at Riske Creek, British Columbia. Contrary to the BHSH, flickers showed significant assortative pairing (P = 0.038) which may result via passive mate choice if yellow and red flickers migrate from allopatric winter ranges. North American band recoveries show red-shafted and yellow-shafted flickers winter on different sides of the Rocky Mountains while red-orange hybrids from Riske Creek winter in the range of red-shafted flickers. Arrival dates of phenotypes did not support the idea that mating patterns are caused passively via different arrival schedules. However, assortative mating patterns did correlate with regional weather patterns along flicker migration routes as well as the North Atlantic Oscillation (NAO) a continental weather pattern that has been shown to influence various aspects of the annual cycle in other birds. If variable weather patterns result in different mating patterns by affecting migration, the geographic location of the northern portion of the zone may be variable due to the migratory behaviour of individuals.<p>There were no differences among yellow, orange and red flickers to win more agonistic contests or have earlier nest initiation dates, larger clutch sizes, greater hatching success, or produce more fledglings. No colour group had a higher likelihood of having a successful compared to a depredated nesting attempt. Aggression was similar between red (N = 21) and yellow flickers (N = 20) during taxidermy model presentations of pure red-shafted and yellow-shafted flickers. Using Akaikes information criterion (AIC) in Program MARK, I determined survival was best modeled as either constant between males and females or varying annually according to weather. Models incorporating HI had less support but suggested that survival is best modeled as a linear relationship where red-shafted flickers have the highest survival. Survival modeled in quadratic relationships found hybrid flickers to have the highest apparent survival estimates in support of the BHSH. Overall there was no support for reduced hybrid fitness, but survival appears to be influenced more by annual variation rather than strictly by an individuals HI. Overall, I failed to find reduced hybrid fitness in support of the DEH but also failed to find increased hybrid fitness as predicted by the BHSH. Annual changes in selection pressure could prevent introgression of hybrid genes throughout the zone if selection favours red-shafted genes in some years and yellow-shafted genes in other years.

<p>Although the majority of the population carries <em>Candida spp</em> as normal components of their microflora, these species are important human pathogens that have the ability to cause disease under conditions of immunosuppression or altered host defenses. The spectrum of disease caused by these species ranges from cutaneous infections of the skin, mouth, esophagus and vagina, to life-threatening systemic disease. Despite increases in drug resistance, the antifungal armamentarium has changed little over the past decade. Thus increasing our understanding of the life cycles of these organisms, not only how they propagate themselves, but also how genetic diversity is created within the population is of considerable import. Additionally expanding our knowledge of key signal transduction cascades that are important for cell survival and response to stress will add in developing new antifungal therapies and strategies. </p><p>This thesis addresses both of these key areas of fungal pathogenesis. In the first chapter, we use genome comparisons between parasexual, asexual, and sexual species of pathogenic <em>Candida</em> as a first approximation to answer the question of whether examining genome content alone can allow us to understand why species have a particular life cycle. We start by examining the structure of the mating type locus (<em>MAT</em>) of two sexual species <em>C. lusitaniae</em> and <em>C. guilliermondii</em>. Interestingly, both species are missing either one or two (respectively) canonical transcription factors suggesting that the control of sexual identity and meiosis in these organisms has been significantly rewired. Mutant analysis of the retained transcription factors is used to understand how sexual identity and sporulation are controlled in these strains. Secondly, based on the observation that these species are missing many key genes involved in mating and meiosis, we use meiotic mapping, SPO11 mutant analysis, and comparative genome hybridization to demonstrate that these species are indeed meiotic, but that the meiosis that occurs is occasional unfaithful generating aneuploid and diploid progeny. </p><p>In the second and third chapters we examine the calcineurin signaling pathway, which is crucial for mediated tolerance to cellular stresses including cations, azole antifungals, and passage through the host bloodstream. First, we show that clinical use of calcineurin inhibitors in combination with azole antifungals does not result in resistance to the combination, suggesting that if non-immunosuppressive analogs could be further developed this combinatorial strategy may have great clinical efficacy. Second, we use previous studies of the calcineurin signaling pathway in <em>S. cerevisiae</em> to direct a candidate gene approach for elucidating other components of this pathway in <em>C. albicans</em>. Specifically, we identify homologs of the <em>RCN1, MID1</em>, and <em>CCH1</em> genes, and use a combination of phenotypic assays and heterologous expression studies to understand the roles of these proteins in <em>C. albicans</em>. Although the mutant strains share some phenotypic properties with calcineurin deletion strains, none completely recapitulate a calcineurin mutant. </p><p>In the last chapter, we examine the plausibility of targeting the homoserine dehyrogenase (Hom6) protein in <em>C. albicans</em> and <em>C. glabrata</em> as a novel antifungal strategy. Studies in <em>S. cerevisiae</em> had demonstrated a synthetic lethality between hom6 and fpr1, the gene encoding FKBP12 a prolyl-isomerase that is the binding target of the immunosuppressant FK506. Thiss synthetic lethality was due to the buildup of a toxic intermediate in the methionine and threonine biosynthetic pathway as a result of deletion of hom6 and inhibition of FKBP12. We deleted <em>HOM6</em> from both <em>C. albicans</em> and the more highly drug-resistant species <em>C. glabrata</em>. Studies suggest that regulation of the threonine and methionine biosynthetic pathway in <em>C. albicans</em> has been rewired such that the synthetic lethality between hom6 and FKBP12 inhibition no longer exists. However, in <em>C. glabrata</em> preliminary analysis suggest that similarly to <em>S. cerevisiae</em> hom6 and inhibition of FKBP12 can result in cell death.</p> / Dissertation

Understanding the processes that govern mating behaviors is a fundamental goal of evolutionary biology and behavioral ecology. Population-level patterns of mate acquisition and offspring production, otherwise known as the genetic mating system, play a central role in the sexual selection on morphological and behavioral traits and may facilitate speciation. The central hypothesis of this research is that variation in environmental conditions, such as temperature, turbidity, and habitat, and demographic influences such as population density, sex ratios and temporal availability of mates, may limit mating and reproductive success in a predictive manner. Therefore the goal of this dissertation is to examine the contributions of geographic and temporal variation on the plasticity of the genetic mating system in two species of pipefish. The first study examined whether meaningful variation in the genetic mating system exists between two natural populations of the dusky pipefish, Syngnathus floridae. Results of this investigation provide evidence that the genetic mating system differs among different geographic locations. The second study considered the relative contributions of environmental conditions and population demographics on differences in the genetic mating system of dusky pipefish from five natural populations. The results of this investigation show strong trends for demographic and environmental factors to strongly influence the genetic mating system between populations. The third study considered how variation in the number of available mates predicts the outcome of sexual selection during the course of a breeding season in the broad-nosed pipefish, Sygnathus typhle. The results of this study indicate a strong influence of the operational sex ratio on the genetic mating system. In addition to these studies, a study was conducted to investigate whether phylogeographic relationships may be responsible for geographic variation in the genetic mating system of the dusky pipefish of pipefish. Mitochondrial DNA analysis does not substantiate subspecies designations for this species and microsatellite analysis show a clear pattern of isolation by distance. Taken together, these studies significantly enhance the understanding of how mating systems are organized over broad environmental gradients and temporal/spatial scales and to the evolution of sexual selection on the whole.

The nematode Caenorhabditis elegans, with its sequenced genome, compact nervous system and stereotyped behaviors is an ideal model organism in which to study the integration of sensory input with motor output. Male mating behavior is among the most complex of these behaviors and males utilize a number of sensory organs in its execution. Among these are the rays, which are nine pairs of sensory organs that are arranged laterally along the male tail. Each ray is composed of two ultra-structurally distinct neuron types, an A type and a B type, surrounded by a glia-like structural cell. Though compositionally identical, each pair of rays maintains a unique, genetically-hardwired identity based on wiring, morphology, and neurotransmitter fate. Three techniques were used to investigate the role of the rays in male mating behavior. First, cauterization of the tips of the rays removed their sensory endings, leading to ray neuron death. Second, a heterologous light-activated cation channel was utilized to activate specific ray neuron types. Finally, ray neuron types were genetically targeted to undergo apoptosis by expression of heterologous caspases. The results show that the rays play important roles in multiple steps of male mating behavior, including contact response, scanning, and turning. The rays as a whole mediate posture change and backing during contact response. The ability to respond to hermaphrodite contact is shared among the rays, as is initiation of backward locomotion, though all rays are required for efficient, prolonged backward scanning. Both A and B neuron types appear capable of initiating contact response. Direct activation of B neurons through ChR2 causes a contact response-like ventral tail flexure, and elimination of both A and B neurons reduces contact response. A neurons additionally have a unique role in turning.

Title from PDF of title page. / Document formatted into pages; contains 69 pages. / Thesis (M.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: I studied the reproductive characteristics and mating systems of a central Florida population of gopher tortoises (Gopherus polyphemus). Using x-radiography, females were monitored for stage in egg-shelling and clutch size. Eggs began to appear on x-ray photographs in the first week of May in both 2001 and 2002; however, fully shelled eggs were not found before the end of May. In total 55% of the females x-rayed were gravid. Clutch sizes ranged from 4-12 with a mean of 7.29, with a mean clutch mass of 40.9 g. Clutch size increased with an increase in mean carapace length and mean plastron length. Mean clutch mass also increased with mean carapace length of females. Hatchlings began to emerge in late August, with incubation times ranging from 83 to 96 days. 50% of the eggs hatched, with 16.2% of the eggs showing no signs of development when opened. Hatchling mass averaged 30.7 g and was positively correlated with egg mass. / ABSTRACT: DNA was extracted from blood samples obtained from females and their offspring, and from the sexually mature males in the population. Nine microsatellite loci were amplified and genotypes constructed for each individual. There is evidence for promiscuous mating in gopher tortoises. Multiple paternity was detected in two of the seven clutches (28.6 %). In the clutches with multiple fathers, fertilization was highly skewed to one male, with primary male fertilizing over 70% of the clutch. Females with multiple-sired clutches were significantly smaller than females with single-sired clutches. Among the clutches assayed only one male fertilized more than one clutch, indicating that insemination of females is evenly spread among males of similar sizes. However, males assigned as fathers were significantly larger than other sampled males which may mean that larger males have an advantage in fertilization of clutches. / ABSTRACT: Conservation efforts should consider the impact of the mating system on reproduction in a population, and the possible impact of the relocation of larger males on recipient populations. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Includes vita. / Title from PDF of title page. / Document formatted into pages; contains 241 pages. / Thesis (Ph.D.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Genetic changes likely occur in wild fish populations as a consequence of interactions with cultured fish, but to what extent do those changes threaten the maintenance of natural genetic diversity and population viability? Following a review and categorization of numerous processes suspected of being agents of post-release genetic change in recipient wild populations (Chapter 1), I focus on risks relating to the magnitude and duration of releases -- but with a twist. That is, I assume that the mean fitness of released, cultured individuals does not differ from that of the recipient natural population. Throughout, attention is devoted to potential post-release changes in inbreeding (NeI) and variance (NeV) effective population sizes -- indicators of expected rates of population-level change in inbreeding and drift variance, respectively. The reductive effect that large-scale releases exert on NeI in recipient populations can be significant. / ABSTRACT: The effect is shown to be a threshold process (Chapter 2) and thus suggestive of an approach for determining risk-adverse stocking (or release) rates. This approach is utilized in Chapter 3, which describes genetic recommendations for an incipient marine stocking program. Several discordant contemporary NeI models are examined mathematically and by computer simulation (Chapter 4). I show that certain published results pertaining to the effect of multiple paternity on NeI are erroneous; a general model is described which accounts for inbreeding and relatedness in and among parents. That model is utilized in an empirical study of gene correlation in a hatchery cohort (Chapter 5). Propagation-related causes of reductions in NeI are also investigated in this cohort. / ABSTRACT: Finally, extending mutational meltdown theory to accommodate fluctuating population sizes and recessive selective effects, I show that when large reductions in NeV occur (such as those that accompany admixtures of cultured and wild fish), the expected time to population inviability is significantly reduced (Chapter 6). Although a more comprehensive theoretical approach is needed, a precautionary inference may be drawn -- aquaculture-induced reductions in Ne, even though they may be transient, can lead to adverse genetic impacts. Avoidance of Ne-reductions cannot be accomplished, in a practical sense, without considering the stocking or release rates of cultured fish. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.