13 of the world’s 19 <i>Araucaria</i> species are endemic to New Caledonia. This thesis has investigated the evolution and systematics of this group. A molecular phylogenetic study based on sequence data from two chloroplast regions resolved all 13 New Caledonian species as a monophyletic group, sister to the Norfolk Island Pine (<i>A. heterophylla</i>). The relationships between the New Caledonian species was not fully resolved as little sequence variability was detected, however, three main groups were defined. The species with bigger leaves occupied a basal polytomy, whereas the vast majority of species with smaller leaves were grouped together in a clade. Within this ‘small leaved’ clade, the three New Caledonian species with a coastal distribution formed another monophyletic group. The timing of the radiation of all these species was tested via a molecular clock approach using different calibration tools (fossil data, geological events, substitution rates). The precise dating of the New Caledonian radiation remains uncertain because different calibration methods give different dates. However, it seems likely to have occurred between 10 and 43 <i>mya.</i> A combination of molecular and morphological approaches was used to assess species limits and population identities. This resulted in re-determination of the identity of several populations and the distributions of some species. The current state of knowledge of the taxonomy of the New Caledonian species was summarised. Finally, the distribution of chloroplast haplotypes among 468 individuals from 49 populations representing all New Caledonian <i>Araucaria</i> revealed strong taxonomic signal, and high genetic diversity among the species with bigger leaves, and low diversity in the coastal species. The distribution of genetic variation is discussed in the context of the evolution and conservation of the New Caledonian <i>Araucaria</i> spp.

No description available.

This thesis addresses the understudied systematics, evolution, biogeography and diversity of the Streptaxidae, a speciose, near pan-tropical family of carnivorous land-snails. A phylogeny of the Streptaxoidea is inferred from nuclear and mitochondrial DNA (114 taxa from Africa, the Indian Ocean, Asia, South America and Europe). Streptaxidae are monophyletic while all subfamilies and several genera are polyphyletic. Subfamily-level clades originate in a basal polytomy, unresolved by morphology, dating to the early Cenozoic, perhaps corresponding to a rapid radiation and the key innovation of penial hooks. Several Cenozoic trans-oceanic dispersals are evident. Each major shell morphology, a penial sheath and a dart like genital stimulator show homoplasy. Peak diversity in East Africa results from speciation among numerous relict lineages. The "streptaxomorph" growth mode unique to certain streptaxids is investigated using Raupian morphometries. In ontogeny, a single deviation of the coiling axis occurs, relating to the angles of inclination of the aperture and between the columellar margin and the axis. This may be an adaptation to environmental regimes. Across taxa streptaxomorphs have relatively narrower shells and larger buccal masses, which may be adaptations to carnivory. A phylogeographic study of Ptychotrema geminatum from forest sites across Uganda is conducted to test competing hypotheses on the location of Pleistocene forest refugia. These were shown to be in low-lying areas of the far west, not montane areas of the south-west, and not on the shores of Lake Victoria. Expansion was episodic and may have involved chance dispersal. Population structure, which is so marked as to suggest cryptic species are present, is not accompanied by morphological change beyond that induced by current environmental conditions. Anatomical data on Streptaxoidea is compiled and considerably added to, to produce a new annotated family- and genus-group classification. Two new subfamilies and at least four new genera are required for known taxa. The megadiverse genus Gulella is redefined and considered to be a species flock within which relationships are unresolved.

No description available.

No description available.

No description available.

The wings of the Nymphalid butterfly, <I>Bicyclus anynana, </I>have a series of eyespot colour patterns, each composed of a white pupil, a black centre and a gold other ring. An eyespot pattern is organised around a group of signalling cells, the focus, that is active during the first hours of pupal development. Positional information, given to the cells around the focus, is translated into rings of differently pigmented scales. One hypothesis for the underlying mechanism is a concentration gradient of a diffusible morphogen produced by the focal cells, and interpreted in a threshold manner by the responding epidermis. If the diffusion gradient model is correct, when two foci are close together, the signals would summate and this effect would be apparent in the detailed shape of the pigment pattern formed. The morphogen gradient hypothesis was tested by measuring areas of fused eyespot patterns in <I>Bicyclus anynana, </I>by grafting focal cells close together, and also by using a mutation (<I>Spotty</I>) that produces adjacent fused eyespots. The results indicate that, in the region between two foci, there is nearly always an extra area of cells differentiating into part of the pattern. The same qualitative results were obtained using a computer model of two sources that, via diffusion, establish two overlapping concentration gradients. I investigated the potential for evolutionary change in the developmental mechanism of eyespot formation by applying artificial selection for various aspects of eyespot phenotype. Selection for color composition of the large dorsal eyespot on the forewing, produced a line of butterflies with a narrow or no gold ring (BLACK) and another line with a reduced black centre and a broad ring (GOLD). Heritabilities were high, giving a rapid response to selection, and other eyespots suffered a correlated change in the proportion of their color rings. Surgical experiments were then performed on pupal wings from the different lines at the time of eyespot pattern determination. Grafting foci between BLACK and GOLD line pupae, and inducing ectopic eyespots by damage, both showed that the additive genetic variance for eyespot composition was at the level of the response component of the developmental mechanism.

No description available.

No description available.

No description available.