Search

Hybridisation and polyploidy are important in the evolution of species. The genus Betula L. is an ideal model to study these processes as species of this genus hybridise frequently and polyploid species are common. In this thesis, I investigated the hybridisation of three Betula species in Britain; the phylogenetic relationships and genome size of all known Betula species, and conducted phylogenomic analysis of diploid Betula species. A cline of introgression of microsatellite marker alleles from B. nana was found extending into B. pubescens populations far to the south of the current B. nana range in Britain. We suggest that this genetic pattern is a footprint of a historical decline and/or northwards shift in the range of B. nana populations due to climate warming in the Holocene. The Atkinson Discriminant Function (ADF) is a leaf-morphology metric to distinguish between B. pubescens and B. pendula. We test it on 944 trees sampled across Britain against species‟ discriminations made using 12 microsatellite loci and found that the accuracy of the ADF can be raised to 97.5% by using an ADF of -2 rather than zero as the boundary line between the species. The taxonomy of the genus Betula is debated and a new classification has been proposed in a recent monograph. We evaluated it using ITS and restriction site associated DNA sequencing (RADSeq). The result based on ITS largely agrees with species classification in the recent monograph but with uncertainties. Phylogenomic analysis of 587 RAD loci for Betula diploid species using coalescence-based methods, a concatenation method and binary presence/absence of RAD loci produced wellresolved trees with similar topology. Based on these analyses, we propose a new classification of Betula into four subgenera and seven sections. Further research is needed to infer the parental origins of polyploid species within Betula.

This thesis is intended to be a comparative approach to Chinese theories of the literary symbolic by way of a comprehensive investigation of the term xing [Chinese symbol]. The xing has a long history of over two thousand years, is capable of protean meanings and generally considered very confusing. In the Introduction of the present work, a historical review of the study of the xing provides a map of the terrain in this area. Following this, a discussion of methodology is unfolded and suggestions are made that the general aim of this thesis is not to search for a "true" or "essential" meaning of the xing, but to examine how the word has actually been used in Chinese literary studies and to explore as much as possible its explicit and potential meanings. The ideal way of approaching an issue of this nature, the thesis suggests, would be a four-fold one, namely, the historical, descriptive, analytical and comparative approach. In this study, comparative approach is in the predominant position. The first part is designed to reveal the meanings of the xing and a number of other relevant terms. Through a descriptive analysis of the statements by major critics in various historical periods and by invoking Western theories of literature, the thesis discusses the multiple meanings of the xing, the intrinsic relationship between these meanings and the nature of poetic creation which underlies them. In the second part, a contour is drawn to demonstrate the mainstreams of Western theories of symbolism from Romanticism to Modernism. A number of important critics, such as Goethe, Coleridge, Carlyle, Mallarme and T. S. Eliot, are discussed and analysed, thus preparing the ground for an all-round comparison. The comparative study in this work is conducted in two ways: 1) Western theories of symbolism are applied to the interpretation of Chinese concepts and 2) Examples are presented to demonstrate the amazing similarities in the way Chinese and Western critics deal with the issue of the literary symbolic, so as to attain a better understanding of both. The xing not only has multiple meanings but its meanings also work on different levels. Hence, the comparison has to be a three dimensional one: xing is compared and contrasted with fu and bi, and these three terms are compared with parallel Western notions of sign, allegory and symbol; moreover, these comparisons are made on four levels - as rhetorical devices, as modes of writing, as aesthetic tendencies and as modes of interpretation. In the concluding chapter, a summary is given highlighting several major points at which the East and the West come closest and an attempt is made to reveal the underlying theoretical reasons.