No description available.

No description available.

No description available.

No description available.

No description available.

Hybridisation is a common evolutionary process that can arise in primary or secondary contact. Gene ow and/or reproductive isolation between hybridising taxa can be explored in hybrid zones. Therefore, a (homoploid) hybrid zone in north-west Spain between Hyacinthoides non-scripta and H. hispanica was studied. The centre occurs west to east across the Galicio-Duero Mountains with H. non-scripta distributed north, and H. hispanica south of the centre. The hybrids' genome sizes and phenotypes represented a range of intermediate states between their parents. Crossing and seed germination experiments revealed a low inter-speci c barrier, and the hybrids showed similarly good tness. Genome wide markers for large genome species were designed from transcriptomes. Diagnostic SNPs between H. non-scripta and H. hispanica were targeted and re-sequenced with multiplexing PCR. Coalescence analyses suggested a Pleistocene origin of parapatric speciation between H. non-scripta and H. hispanica. These results are supported by shared inter-speci c polymorphisms, the lack of recent hybrid generations and of parental individuals in sympatry. Di erential introgression patterns between the organellar and nuclear genomes revealed that formerly H. hispanica ranged further north but was swamped by H. non-scripta alleles. Asymmetric hybridisation was reasoned by absence of backcrosses between northern hybrids to H. non-scripta, but presence between southern hybrids and H. hispanica. Combining these results, a southwards movement of the hybrid zone centre caused by climate change (and adaptive introgression), or inter-speci c di erences in owering time was suggested. Cline patterns revealed cyto-nuclear incompatibilities, which could evolve through divergent adaptation of the organelle to climate and a delayed selection on nuclear inter-acting loci. Both species are in secondary contact in the UK due to recent introduction(s) of H. hispanica and garden variants, which is considered to cause genetic pollution of native H. non-scripta. Therefore, a conservation study is in progress, in which this diagnostic marker system for bluebells is applied.

Hybridisation is increasingly acknowledged as a conservation problem. The widespread hybridisation between grey duck (Anas superciliosa) and mallard (A. platyrhynchos) in New Zealand is a good example of a native species hybridising with a foreign one, and forms the main focus of this thesis. Mallards were introduced into New Zealand from Europe, and hybrids were soon observed. I surveyed the extent of the hybridisation on the West Coast of the South Island and found that, based on phenotype, at least half of population is now hybrids. Mallards and mallard-like hybrids dominate in the eastern South Island, while grey ducks occur only in some areas of the West Coast. Comparison with historical data suggests that the decline of the grey duck and the spread of hybrids has not stabilised and is ongoing. Contrary to expectations most grey ducks were found on agricultural land and most mallards on natural lakes or rivers, so grey ducks probably do not have an advantage over mallards on the less developed West Coast. An alternative theory is proposed here that explains the spatial distribution of hybridisation as a reflection of a temporal pattern. As mallards were first released in the east, the delay taken to cross the Southern Alps could also explain the pattern observed. This hypothesis suggests that the grey duck will persist in the southern West Coast. An analysis of the phenotypes of partners in pairs suggests that mating is positively assortative within each species and within hybrids. In fact, not a single pair of pure grey duck mated with pure mallard was observed in almost a thousand pairs, raising the question of how hybridisation started. There was a tendency for males to be more mallard-like in phenotype than their partners, suggesting there might be a selective advantage to the mallard male phenotype. This may be one factor explaining the dominance of mallards in the hybrid swarm. To analyse hybridisation at the genetic level, I analysed samples from grey ducks, mallards and domestic ducks with 11 microsatellite loci. This genotyping profile was then compared to ducks captured and shot in New Zealand. Genetic analysis confirms that the ducks in New Zealand were almost exclusively of hybrid origin. Phenotypic hybrid scores correlated with the established genotypic scores, but the correlation was imperfect, suggesting inaccuracies in either or both measures. As the spread of hybrids might be due to the differences in their fitness relative to either parent species, I compared the relative fitness of hybrid ducks using a range of health-related measures such as ecto- and endoparasite loads, immunocompetence, body condition, and heterophil to lymphocyte ratios. Overall, I found no conclusive evidence for any differences between grey duck-like and mallard-like individuals. However, as my sample consisted nearly entirely of hybrids, it is possible that fitness may differ from the parental species. To understand the outcome of hybridisation between two species, I next constructed a mathematical model to simulate hybridisation, and which allowed the specification of parameters describing mating patterns, differential survival, and differential reproductive output. The model successfully predicted the outcomes of two known hybridisation cases. In a sensitivity analysis for mallard and grey duck, the model predicted that this species pair is likely to hybridise under any set of conditions likely to be encountered across their shared range. Finally, in a study within the more general context of hybridisation, the influence of inbreeding on hybridisation rates was investigated using inbred and outbred lines of Drosophila species. I found evidence for increased hybridisation in inbred lines, and although further studies are needed to confirm the generality of this pattern, my results have implications for the management of hybridisation, and for the use of hybridisation as an adaptive strategy. In conclusion, my work suggests it is very likely that the grey duck will become extinct as a separate species in New Zealand in the near future, and that it is likely to be threatened in other areas of its range were it co-occurs with the mallard. The options for management of this situation are limited, as large areas without mallards are lacking. Captive breeding, or the management of grey duck populations on isolated islands appear the only feasible options. It seems unlikely that hybridisation can be reversed on the mainland, and a homogenous hybrid population is likely to eventually occupy the entire range of the grey duck across New Zealand.

The binding of a novel GABAs receptor radioligand eH]-CGP62349 to human hippocampal control and epileptic sections was investigated using quantitative receptor autoradiography. Kinetic analyses performed on rat brain sections, to conserve the use of human tissues, demonstrate that eH]-CGP62349 associated rapidly. The same radioligand dissociated rapidly initially, then very slowly. Utilising human hippocampus it was shown that CH]-CGP62349 bound with high affinity (O.SnM) to human control hippocampal sections. The kinetics of GABAs receptor in human hippocampus using the novel compound confirmed previous studies performed in rat membrane. The localisation of GABAB receptors in human hippocampal control partially supported former studies using agonist ligands such as CH]-GABA and eH]-baclofen, despite differences have been noticed. Hippocampal slices from surgical resected specimens obtained from hippocampal sclerotic (HS)/temporal lobe epilepsy (TLE) patients were compared with neurologically normal post-mortem control subjects for neuropathology and GABAs receptor density and affinity. Neuronal loss was observed in most of the hippocampal subregions, whereas in subiculum any significant difference was detected. For GABAa receptor density (Bmax) a significant reduction was reported in CA3, CA4, and DG; the affinity was increased exclusively in DG. After the correction of Bmax value for the neuronal loss a significant increase was seen in CA3. Oligonucleotides were designed to investigate the two GABAB1 isoforms (la, and lb), and the GABAa2 subunit in human hippocampal control and HSITLE tissues, obtained as well as for the autoradiography. GABAsla, GABAB1b, and GABAB2 transcript distribution was in agreement with the receptor protein localisation, even though in the human hippocampus GABAa2 has to be yet localised and to verify if it is associated with GABAsla or GABABlbto form the dimeric active receptor. The present study suggests an involvement of GABABreceptors in HS/TLE in some not all the hippocampal subregions in terms of receptor density and affinity. Further investigations in regard to the quantitative in situ hybridisation data and the immunocytochemical results are fundamental to gain insight into the pathological role of GABAs receptors.

No description available.

The investigation of hybrid zones has proven to be one of the most promising approaches to advance our understanding of species barriers, and to elucidate evolutionary processes involved in speciation. Due to the improvement of molecular techniques it will soon be possible to investigate the genetic composition of non-model species in much greater detail, and also include species that defy investigation using controlled laboratory conditions. To be able to draw further reaching conclusions about the generality of certain evolutionary factors, it is crucial to investigate a wide spectrum of organisms differing in traits, life histories and relatedness. This study investigates patterns of hybridisation between two pairs of closely related species in the genus Rhododendron. AFLP data for 346 loci, from twelve populations in total comprising 390 individuals, were obtained. Additionally, the abundance of three alkane components in the leaf waxes of 115 individuals was determined. For the species pair R. clementinae and R. roxieanum low levels of recent hybridisation were found, however, the wax composition of R. roxieanum var. cucullatum suggests historical introgression. Two types of hybrid zones were found for R. aganniphum and R. phaeochrysum, one mainly comprising F1 individuals, and the other frequent backcrosses to R. aganniphum. Furthermore, evidence for genomic incompatibilities at several loci for the two species will be presented, and hybrid identity of R. aganniphum var. avorufum and R. phaeochrysum var. agglutinatum is suggested.