The objective of this research was to investigate lead speciation in the soil/sediment-water environment and to better understand how the species affect lead mobility under different environmental conditions. The research involved both field soil and sediment samples as well as standard lead solutions. Field samples were fully characterized and extracted by aqueous and organic solvents. The results were compared and evaluated with the metal speciation model, MINTEQA2. Hydrolytic polymerization and organic complexation studies were conducted with standard lead solutions under controlled experimental conditions. Results of the field samples showed that pH, dissolved cations, ionic strength, dissolved organic matter, and nature of the soil/sediment matrix play major roles in the distribution and mobility of lead (Pb) from contaminated sites. In the aqueous equilibration experiment, the magnitude of Pb2+ solubilization was in the order of pH4>pH7>pH9. The results were in good agreement with MINTEQA2 predictions. An important finding of the research is the detection of Pb polymerization species under controlled experimental conditions. At pH 5.22, Pb polymeric species were formed at rate of 0.03 per day. The role of Pb complexation with organic matter was evaluated in both field and standard samples. Different methodologies showed three types of organically bound Pb. A very small fraction of Pb, in the ppb range, was extractable from the contaminated soil by polar organic solvents. Sequential extractions show that 16.6±1.4 % of the Pb is organically complexed. Complexation of Pb with fulvic acid provided new information on the extent of Pb association with soluble organic matter. The overall results of this research have provided new and useful information regarding Pb speciation in environmental samples. The results, in several instances, have provided verification of MINTEQA2 model's prediction. They also revealed areas of disagreement between the models prediction and the experimental results. A positive note regarding the experimental work done in the research is the verification of the mass balance in all the repeated experiments.

BACKGROUND:Numerous studies have investigated cospeciation between parasites and their hosts, but there have been few studies concerning parasitoids and insect hosts. The high diversity and host specialization observed in Anicetus species suggest that speciation and adaptive radiation might take place with species diversification in scale insect hosts. Here we examined the evolutionary history of the association between Anicetus species and their scale insect hosts via distance-based and tree-based methods.RESULTS:A total of 94 Anicetus individuals (nine parasitoid species) and 113 scale insect individuals (seven host species) from 14 provinces in China were collected in the present study. DNA sequence data from a mitochondrial gene (COI) and a nuclear ribosomal gene (28S D2 region) were used to reconstruct the phylogenies of Anicetus species and their hosts. The distance-based analysis showed a significant fit between Anicetus species and their hosts, but tree-based analyses suggested that this significant signal could be observed only when the cost of host-switching was high, indicating the presence of parasite sorting on related host species.CONCLUSIONS:This study, based on extensive rearing of parasitoids and species identification, provides strong evidence for a prevalence of sorting events and high host specificity in the genus Anicetus, offering insights into the diversification process of Anicetus species parasitizing scale insects.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Separation of the metal ions Cu2+, Pb2+, Cd2+ Mn2+, Cr3+, Fe3+ and Zn2+ with poly ethylenediamine tetra-acetic acid (EDTA), ethylenediamine disuccinic acid ([S,S']- EDDS) and ethylenediamine dimalonic acid (EDDM) was performed by Capillary Electrophoresis. The electropherograms obtained by Capillary Electrophoresis were validated with a speciation model Joint Expert Speciation System (JESS). Excellent agreement was observed for the speciation diagrams for these species with the pH curves determined by capillary electrophoresis with those determined by speciation modelling using JESS. The ligands EDDS and EDDM are readily biodegradable. They have been proposed as substitute ligands for EDTA. Detection of the above species was performed using both an electrochemical and a UV detector. The obtained electropherograms were used for the determination of the detection limits of these species. The electrochemical detector has a lower detection limit for these species than the UV detector in conformity with reported literature for these detectors. / AFRIKAANSE OPSOMMING: Skeiding van die metaal ione Cu2+, Pb2+, Cd2+, Cr3+, Fe3+ en Zn2+ met behulp van etileendiamientetra-asyn suur (EDTA), etileendiamiendisuksien suur ([S,S']-EDDS) en etileendiamiendimaleen suur (EDDM) was gedoen deur kapilêre elektroferose. Die elektroferogramme, verkry deur kapilêre elektroferose was gebruik om die spesiasie model "Joint Expert Speciation System (JESS)" te valideer. Uitstekende ooreenstemming was waargeneem vir die verspreidings diagramme van hierdie spesies as 'n funksie van pH wat verkry was deur kapilêre elektroferose met die' wat vasgestel was deur die spesiasie modeleeringsproses van JESS. Die ligande EDDS en EDDM toon onmiddelike biodigradeerbaarheid. Hulle was voorgehou as alternatiewe ligande vir EDTA. Bepaling van die bogenoemde spesies was ook gedoen deur beide elektrochemiese en UV deteksie. Deur gebruik te maak van hierdie detektore was die deteksie limiete van hierdie spesies bepaal. Die elektroochemiese detektor het 'n laer deteksie limiet vir hierdie spesies in vergelyking met die UV detector. Dit stem ooreen met die literatuur vir hierdie detektore.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Separation of the metal ions Cu2+, Pb2+, Cd2+ Mn2+, Cr3+, Fe3+ and Zn2+ with poly ethylenediamine tetra-acetic acid (EDTA), ethylenediamine disuccinic acid ([S,S']- EDDS) and ethylenediamine dimalonic acid (EDDM) was performed by Capillary Electrophoresis. The electropherograms obtained by Capillary Electrophoresis were validated with a speciation model Joint Expert Speciation System (JESS). Excellent agreement was observed for the speciation diagrams for these species with the pH curves determined by capillary electrophoresis with those determined by speciation modelling using JESS. The ligands EDDS and EDDM are readily biodegradable. They have been proposed as substitute ligands for EDTA. Detection of the above species was performed using both an electrochemical and a UV detector. The obtained electropherograms were used for the determination of the detection limits of these species. The electrochemical detector has a lower detection limit for these species than the UV detector in conformity with reported literature for these detectors. / AFRIKAANSE OPSOMMING: Skeiding van die metaal ione Cu2+, Pb2+, Cd2+, Cr3+, Fe3+ en Zn2+ met behulp van etileendiamientetra-asyn suur (EDTA), etileendiamiendisuksien suur ([S,S']-EDDS) en etileendiamiendimaleen suur (EDDM) was gedoen deur kapilêre elektroferose. Die elektroferogramme, verkry deur kapilêre elektroferose was gebruik om die spesiasie model "Joint Expert Speciation System (JESS)" te valideer. Uitstekende ooreenstemming was waargeneem vir die verspreidings diagramme van hierdie spesies as 'n funksie van pH wat verkry was deur kapilêre elektroferose met die' wat vasgestel was deur die spesiasie modeleeringsproses van JESS. Die ligande EDDS en EDDM toon onmiddelike biodigradeerbaarheid. Hulle was voorgehou as alternatiewe ligande vir EDT A. Bepaling van die bogenoemde spesies was ook gedoen deur beide elektrochemiese en UV deteksie. Deur gebruik te maak van hierdie detektore was die deteksie limiete van hierdie spesies bepaal. Die elektroochemiese detektor het 'n laer deteksie limiet vir hierdie spesies in vergelyking met die UV detector. Dit stem ooreen met die literatuur vir hierdie detektore.

Determining the genetic basis of reproductive isolation is a fundamental goal in evolutionary biology. Intrinsic reproductive isolation often arises due to epistasis between divergent interacting genes. The rapid evolution of hybrid male sterility is known to have several causes, including the exposure of recessive X-linked incompatibilities in males and the rapid evolution of male reproductive traits. Despite these insights, little is known about the genetics of reproductive isolation during the early stages of speciation. This deficiency inspired parallel studies on the molecular evolution of male reproduction in house mice and the genetic basis of hybrid male sterility between two mouse species, Mus domesticus and M. musculus. Evolutionary analysis of 946 genes showed that the intensity of positive selection varies across sperm development and acts primarily on phenotypes that develop late in spermatogenesis (Appendix A). Several reciprocal crosses between wild-derived strains of M. musculus and M. domesticus were used to examine F1 hybrid male sterility (Appendix B). These crosses revealed hybrid male sterility linked to the M. musculus X chromosome and a novel sterility polymorphism within M. musculus. A large introgression experiment was used to further dissect the genetic basis of X-linked incompatibilities between M. musculus and M. domesticus (Appendix C). Introgression of the M. musculus X chromosome into a M. domesticus genetic background produced male sterility and involved a minimum of four factors. No sterility factors were uncovered on the M. domesticus X chromosome. These data demonstrate the complex genetic basis of hybrid sterility in mice and provide numerous X-linked candidate sterility genes. The molecular evolution of five rapidly evolving candidate genes was examined using population and phylogenetic sampling in Mus (Appendix D). Four of these loci showed evidence of positive natural selection. One locus, 4933436I01Rik, showed divergent protein evolution between M. domesticus and M. musculus and was one of a handful of testis-expressed genes within a narrow interval involved in hybrid male sterility. In summary, these data demonstrate that hybrid male sterility has a complex genetic basis between two closely related species of house mice and provide a foundation for the identification of specific mutations that isolate these species.

Despite over seven decades of speciation research and 25 years of phylogeographic studies, a comprehensive understanding of mechanisms that generate biological species remains elusive. In temperate zones, the pervasiveness of range fragmentation and subsequent range expansions suggests that secondary contact between diverging lineages may be important in the evolution of species. Thus, such contact zones provide compelling opportunities to investigate evolutionary processes, particularly the roles of geographical isolation in initiating, and indirect selection against hybrids in completing (reinforcement), the evolution of reproductive isolation and speciation. The spring peeper (Pseudacris crucifer) has six well-supported mitochondrial lineages many of which are now in secondary contact. Here I investigate the evolutionary consequences of secondary contact of two such lineages (Eastern and Interior) in Southwestern Ontario using genetic, morphological, acoustical, experimental, and behavioural evidence to show accentuated divergence of the mate recognition system in sympatry. Mitochondrial and microsatellite data distinguish these two lineages but also show ongoing hybridization. Bayesian assignment tests and cline analysis imply asymmetrical introgression of Eastern lineage nuclear markers into Interior populations. Male calls are divergent between Eastern and Interior allopatric populations and show asymmetrical reproductive character displacement in sympatry. Female preference of pure lineage individuals is also exaggerated in sympatry, with hybrids showing intermediate traits and preference. I suggest that these patterns are most consistent with secondary reinforcement. I assessed levels of post-zygotic isolation between the Eastern and Interior lineages using a laboratory hybridization experiment. Hybrid tadpoles showed equal to or greater fitness than their pure lineage counterparts, but this may be countered through competition. More deformities and developmental anomalies in hybrid tadpoles further suggest post-zygotic isolation. Despite evidence for pre-mating isolation between the two lineages, isolation appears incomplete (i.e. hybridization is ongoing). I hypothesize that potentially less attractive hybrids may circumvent female choice by adopting satellite behaviour. Although mating tactics are related to body size, genetic status may play a role. I show that pure Eastern males almost always engage in calling, while hybrids adopt a satellite tactic. An absence of assortative mating, despite evidence of female preference, suggests successful satellite interception possibly facilitating introgression. / Thesis (Ph.D, Biology) -- Queen's University, 2013-03-04 16:01:33.892

Oceanographic features such as currents, fronts and upwelling cells have been recognised as possible factors driving population differentiation within species. The Benguela Current is one of the oldest upwelling systems in the world, located off the west coast of Southern Africa, and represents a biogeographical boundary between the Atlantic and Indo-Pacific Oceans. Previous studies have reported the influence of this system in isolating several marine taxa between the two oceans. However, few have been conducted within the Benguela Current boundaries, in order to understand its role in shaping population genetic structure of fish species at a regional level. The present study documents the influence of the Benguela Current oceanographic features on the genetic differentiation, population connectivity and evolutionary history of five coastal fish species (Diplodus capensis, Argyrosomus inodorus, Argyrosomus coronus, Atractoscion aequidens and Lichia amia), and one oceanic pelagic fish species (Thunnus albacares). Results for both mitochondrial and nuclear marker variation in all coastal species revealed a similar geographical pattern of population genetic structuring despite distinct differences in life history features. The oceanic species exhibited shallow population differentiation between Atlantic and Indian Oceans. For coastal species, different depths of differentiation were observed, ranging from speciation events (A. aequidens, A. coronus and A. japonicus) to shallow structuring (A. inodorus and T. albacares). Furthermore, in these cases, population structures were coincident with the Benguela Current oceanographic features, suggesting that the system may represent a vicariant barrier to dispersal of coastal fish species. Congruence between mitochondrial and nuclear markers suggests that population isolation was not a single historical event, but has persisted over large timescales and is still active. The existence of cryptic speciation events, and the high levels of genetic diversity and differentiation documented make the Benguela Current a natural laboratory to study evolutionary mechanisms shaping biodiversity and genetic population structure of marine fish species.

Barriers to interbreeding limit gene flow between sister taxa, leading to reproductive isolation and the maintenance of distinct species. These barriers come in many forms, and can act at different stages in the reproductive process. Pre-copulatory barriers may be due to individuals discriminating against heterospecifics in mate choice decisions. These decisions may be informed through a range of sensory modalities. If a female is mated and inseminated, then there may be multiple postmating-prezygotic barriers that affect the success of heterospecific sperm in attaining fertilisations. Post-zygotic barriers can be very early acting, resulting in embryonic fatality, or may be later acting, affecting the fitness of hybrid offspring. In this thesis I investigate potential reproductive barriers between the interbreeding field crickets Gryllus bimaculatus and G. campestris. I find that females of both species show only weak preference for conspecific calling song, and may even respond phonotactically to songs typical of heterospecific males. Female G. bimaculatus are repeatable in their preferences and strength of response. G. bimaculatus females presented with synthetic songs prefer those with longer inter-pulse intervals, whereas G. campestris show no discrimination between these songs. Upon meeting, G. campestris females strongly discriminate against heterospecific males, behaving aggressively towards them. This is likely driven by females responding to close range species recognition cues, including chemoreception. The species differ in their cuticular hydrocarbon profiles, and females that are no longer able to use their antennae to receive chemosensory information reduced their aggressive behaviour towards heterospecific males. G. bimaculatus females will mate with heterospecific males, though less readily than to conspecifics. When sequentially mated to both conspecific and heterospecific males, these females will preferentially take up and store sperm from the conspecific male, and sperm from conspecific males is more likely to sire offspring than would be predicted from the proportion of sperm in storage. Eggs from inter-species mating pairs are less likely to begin embryogenesis, and are more likely to suffer developmental arrest during the early stages of embryogenesis. However hybrid embryos that survive to later stages of development have hatching success similar to that of pure-bred embryos. After mating, phonotaxis of G. bimaculatus females towards male songs follows a pattern of suppression and subsequent recovery, likely triggered through detection of seminal proteins transferred in the male ejaculate, or detection of mechanical filling of the spermatheca. This pattern of suppression and recovery of phonotaxis does not differ between females mated to conspecific or heterospecific males. Females that lay few or no eggs do not experience a refractory period.

Electrophoretic variation in 18 proteins encoded by 20 autosomal loci was used to compare the genetic relationships of 19 natural populations representing three species of the subgenus Neotoma. Of the 20 loci examined nine were monomorphic and fixed for the same allele in all populations. No more than seven loci were polymorphic within a single population. Genetic variability was expressed as the proportion of loci heterozygous in the average individual of a population. Heterozygosity in the three species of Neotoma studied averaged 0.078, a value within the range reported for other rodents. Although the levels of heterozygosity seen in Neotoma could not readily be explained, the variation may be attributed to ecological factors. The three species of Neotoma were compared on the basis of genetic similarity and found to form a close taxonomic unit, probably semispecies. Divergence times were obtained for the three species and found to compare well with divergence times obtained from fossil data. In general, the three species have diverged within the last 112,000 years during the Wisconsin glacial period.

Investigations of host-associated differentiation of parasitoids have largely focused on the degree of molecular genetic differentiation, but a true test of species status must examine the mating patterns of differentiated populations to determine if they can interbreed in the wild and produce viable offspring. We examined possible mechanisms of isolation between two genetically distinct host-plant complex races of the braconid, Cotesia congregata, originating from hosts on tobacco and catalpa. We compared male responses to female pheromones, elements of male acoustic courtship signals, and breeding success between the two races. Males responded to pheromones from both sources and male courtship signals showed only subtle differences, suggesting that factors other than courtship behavior may be involved in isolation of the two races. However, nearly 90% of females from one hybrid cross failed to produce offspring, leading to post-zygotic isolation. Development time, emerged brood size, and sex ratios between the races also differed.