Regulatory evolution of genes controlling development is widely considered to be the major driving force of morphological change in the evolution of animal lineages. The regulation of genes is controlled by interactions between trans-acting factors and cis-regulatory DNA. The evolution of the interaction between the bicoid and hunchback genes is studied by comparing this orthologous interaction in Drosophila melanogaster with the housefly, Musca domestica. A genomic clone of the hunchback region from Musca domestica from an earlier work was characterised by restriction mapping and sequencing. A promoter region upstream of an early embryonically expressed transcript was mapped to the hunchback genomic sequence. Sites of specific interaction between a bacterially-derived Musca domestica BICOID homeodomain protein were mapped to the promoter by DNaseI footprinting. The hunchback regulatory sequence of Musca domestica are unalignable with Drosophila melanogaster; nevertheless, similar patterns of repetitive sequence distribution were found by computer-aided analysis, which suggest extensive slippage-like processes may have been important in the evolution of the hunchback region. A promoter element of Musca domestica hunchback drives a bicoid-dependent pattern of expression in the anterior of transgenic Drosophila melanogaster embryos. A later ectopic expression points to a functional divergence of promoter recognition between the two species. The in vitro DNA-binding function of the Musca domestica BICOID homeodomain was further characterised by quantitative gel-shift assays. The data suggest that the homeodomain differences between Musca domestica and Drosophila melanogaster reflect differences in sequence recognition. The homeodomain differences may have co-evolved with the binding site sequences in the hunchback promoters. It is argued that molecular coevolution of the BICOID trans-factor and cis-binding sites in the hunchback promoter has accompanied a divergence in embryonic size between Musca domestica and Drosophila melanogaster.

P elements have invaded and spread through populations of Drosophila melanogaster in the last sixty years, despite the induction of a severe set of genetic abnormalities known as hybrid dysgenesis (HD). P element spread has occurred because of the co-evolution of several systems that repress P element transposition and HD. Such repression systems, singly or in combination, give rise to populations phenotypically defined as P, M' and Q, with Q further subdivided in Qmat (strong repression transmitted maternally only) and Qbip (strong repression transmitted biparentally). What are the evolutionary dynamics of these repression systems? Do they co-exist or will all populations subsequently gravitate towards one stable system? Qbip populations possess all of the fitness benefits of P, M' and Qmat strains, but have none of their apparent disadvantages. A type I deletion element, called SR, has been isolated from a Qbip strain and its presence has been demonstrated to correlate with strong repression. My thesis tests a working model that the Qbip phenotype, mediated by SR or 'SR-like' elements, is the evolutionary stable state for repression. A D. melanogaster strain devoid of P elements was transformed with SR. Gonadal dysgenesis assays failed to detect strong repression, but the more sensitive A4-4 eye-colour assay failed to detected intermediate strength repression that may be dependent on genomic position. Molecular analysis of naturally occurring Q stains revealed the existence of putative 'SR-like' elements which fulfil the structural requirements of strong repressors. Molecular and phenotypic analysis of flies from a cline on the east coast of Australia, which ten years ago had P populations in the north, Q at central sites and M' in the south, shows that Q and M' flies have increased their range at the expense of P lines. Competition cage experiments which comprise mixtures of repression systems indicate potential trends towards Qbip. The data support the proposition that Qbip is the evolutionary end state for repression in D. melanogaster.

In Drosophila melanogaster, the male produces a song during courtship which is characterised by interpulse intervals, (IPIs), which oscillate around a mean of 30-40 ms. The song characteristics of Australian population of D. melanogaster collected from various latitudes were studied. Because a wide variation of IPI was noted, a selection protocol was performed on single isofemale lines. Males producing long or short IPI's were mated to related females, resulting in two lines of flies singing with long and short IPI means. The selected lines were stored for 32 months without further selection. Regular sampling of these lines showed that the IPI difference was maintained. To understand the genetics of IPI, the long and short lines were mated together. The long line was also mated to a line of Kenyan lines which was found to sing with an unusually short IPI. Analysis of the results showed that although father-son realized heritability was low, there were significant autosomal dominance effects which together reduced IPI by 2-3 ms. Competitive mating tests were undertaken. D. melanogaster had a preference for males producing long song. However it was noted that the long IPI males had larger body size. A screening programme of the Australian flies was undertaken to study the relationship between IPI, body size, latitude and altitude. James et al. (1993) had demonstrated a correlation between latitude and body size. This was confirmed by these experiments, with larger flies existing in cooler latitudes. There was also a correlation between IPI and latitude, with flies from higher latitudes singing with longer IPIs. There was no significant correlation between IPI and body size, or IPI and altitude. The search for IPI variants was extended to include flies from Israel and Kenya. The implications of microhabitats and local environments are also discussed.

Phosphoinositide 3-kinase (PI3K) plays an important role in cellular signalling by generating phospholipid second messengers at the plasma membrane. A large repertoire of signalling and actin-binding proteins, which consistently regulate the dynamic assembly and spatial organisation of actin filaments, binds phospholipid second messengers, through their pleckstrin homology (PH) domains, and regulates changes in actin cytoskeleton dynamics and organisation in response to external stimuli. Thus, the actin cytoskeleton, which functions in the generation and maintenance of cell morphology and polarity, regulation of endocytosis and intracellular trafficking, contractility, motility and cell division, is considered as an integral part of the cell signal transduction system. PI3K-dependent actin cytoskeleton reorganisation has been the subject of intensive studies, as alteration in the cytoskeleton and thus in cell morphology and migration appear to be common signatures of malignancy where PI3K activation is significantly involved. PI3K- dependent regulation of actin cytoskeleton dynamics is proposed to be achieved by cross-talk with the Rho-family small GTPases, major regulators of actin cytoskeleton organisation. However, the molecular mechanisms behind PI3K-dependent actin reorganisation and their interaction with small GTPases in not yet clearly defined. The aim of this project was to investigate the role of the PI3K signalling in controlling actin cytoskeleton, and to explore possible common targets of PI3K and Rho-family small GTPase signalling pathways, as well as to search for new targets downstream of PI3K. Initially, the role of PI3K in the regulation of the actin cytoskeleton in Drosophila cells was defined. Furthermore, a "loss-of-function approach" based on RNA interference for genes involved in PI3K and small GTPase signalling was combined with quantitative differential protein expression analysis and mass spectrometry. The differentially expressed proteins, many of which were cytoskeleton proteins, metabolic and redox enzymes, were linked to signalling pathways and associated with the morphological phenotype of each knockdown. Finally, the research was focused on studying the regulation of phosphorylation of cofilin, an actin depolymerising protein. It has been established that cofilin phosphorylation and activity is not directly regulated by upstream signalling events, but by changes in the levels of filamentous actin itself, with slingshot, the cofilin phosphatase, being a key regulator in sensing the dynamic changes in F-actin levels. Thus, cofilin phosphorylation is a homeostatic sensor of actin polymerisation, which self-limits protrusive response to external stimuli.

In D. melanogaster the period (per) and timeless (tim) genes form a feedback loop that rhythmically inhibits their own transcription. This mechanism creates a twenty four hour clock that regulates many of the flies behavioural and molecular circadian cycles. The conservation of at least per as part of this molecular mechanism in mammals suggests that clock gene functions are well conserved across the animal kingdom. However analysis of per and tim functions in Antherea pernyi and Musca domestica illustrated that the function of the genes did not comply with the D. melanogaster feedback model, and that the genes functions may have diverged significantly within the insects. To further test this divergence of function, analysis of the per and tim function was performed on D. virlis and D. pseudoobscura and extended in Musca. The functional analysis confirmed that Musca PER does not obeying the D. melanogaster circadian clock model. In particular it does not cycle in abundance or subcellular localisation. Furthermore the timing cycles of per and tim transcripts are significantly different between D. virilis and D. pseudoobscura and D. melanogaster. Furthermore unusual PER and TIM cycles in D. virilis suggest that it may have a quite different method of generating a twenty four hour cycle. All of which suggests that the genetic mechanisms behind the molecular clocks of the insects have undergone widespread changes over evolutionary history, and may mean that they are a target for change during speciation events.

No description available.

The aim of this work was to study the distribution of the Simuliidae of Scotland, and to investigate the ecological characters of Scottish species more extensively than had been attempted by former workers. Credit for having been the first to look into the problem of the distribution and ecology of black-flies in Britain is assigned to Edwards (1915, 1920), and Smart (1936) in a paper on the Simuliidae of Fortingal, Perthshire, furnished a foundation for the distribution of the species in that locality. It was realised, however, that as certain important details were omitted in those papers, further study was desirable. More recently in England the important question of the effect of the chemical composition of stream water on the immature stages of Simulium was considered by Pentelow (1935, 1937) in a survey of the non-tidal reaches of the river Tees.

The control of mosquito populations to limit their capacity to spread disease is a topic of pressing international concern, but is one that hinges on a thorough understanding of the mating ecology of these insects. In this thesis we focus on two aspects of mosquito behaviour that are central to their reproductive cycle: mate interaction and swarm formation. Much evidence indicates that mosquitoes use sound frequencies, and specifically those made by the beating wings of their neighbours, as a means to interact with one another. We investigate the role of acoustics in the aforementioned behaviours, using empirical analytical and computational approaches. We contend that a lack of existing quantitative analysis in this field has primarily been driven by the absence of sophisticated data processing tools to researchers. Vie develop a set of advanced frequency extraction techniques that can be used to investigate mosquito flight tone signals. After describing a controlled laboratory set-up that enables the acquisition of high-quality acoustic data, we introduce a signal processing framework (based on the concept of instantaneous frequency) that facilitates efficient, automated extraction of wing beat frequencies from sound recordings of individual tethered mosquitoes. Our methodology gives vast improvement in both time and frequency resolution over previous reports, and encourages the development of new analytical techniques to study flight tone properties. We extend these approaches to study pairwise interactions. We specifically test the phenomenon of harmonic convergence between mosquito couples, whereby males and females are observed to mutually tune their flight tones to some shared frequency. A thorough and exhaustive consideration of this process is provided, from a strictly data-driven perspective, with detailed comparisons to same sex interactions. We find active frequency modulation to be a salient feature of pairwise interactions. However, our data suggest a much greater diversity of interaction than has previously been considered, particularly in the same sex case.

It is generally assumed that the reproductive success of both males and females is not limited by the availability of ejaculates. However, when male ejaculate production is physiologically constrained, the maintenance of high fertility can be an important determinant of fitness. Under the phenotype-linked fertility hypothesis, females can maximise their fertility by choosing mates on the basis of external phenotypic indicators (exaggerated sexual ornaments or displays) of male reproductive quality. I test the phenotype-linked fertility hypothesis in the stalk-eyed fly Cyrtodiopsis dalmanni, a species characterised by sexual dimorphism in the length of the eyestalks that project laterally from the head (eyespan). I demonstrate that females prefer large eyespan males as mates and exhibit higher fertility when housed with large eyespan males than when housed with small eyespan males. I also show that male eyespan predicts the growth rates and final sizes of the accessory glands and testes of males raised under different levels of nutritional stress. Thus male eyespan is a reliable indicator of male reproductive quality, and female preference for this trait can directly increase female fitness through fertility assurance. The higher fertility of large eyespan males is associated with the ability to copulate at a higher frequency rather than greater success on a per-mating basis. Using artificial selection experiments and behavioural observations, I provide evidence that male mating frequency is physiologically constrained by the size of the accessory glands. As eyespan reflects male accessory gland size, females can improve their chances of obtaining an ejaculate by choosing mates with large eyespan. Moreover, I show that males allocate larger ejaculates to females that offer a greater number of fertilisation opportunities. Based on my results, I have proposed a physiological mechanism for the signalling of male mating frequency by male eyespan mediated by circulating levels of juvenile hormone.

The ecology and reproductive strategies of seven species of domestic Drosophila were examined at a wholesale fruit and vegetable market. The seasonal abundance of adult Drosophila was investigated using baited traps. The value of different trapping methods was discussed. Drosophila were reared from different fruits and vegetables brought back from the market to the laboratory. D. melanogaster, D. simulans and D. subobscura nearly always emerged from fermenting fruits, D. busckii specialised on decaying vegetables, and D. immigrans and D. hydei were generalists. Within the groups, fermenting fruit and decaying vegetables there was considerable overlap of breeding sites. Some of the factors which might influence breeding site preferences were investigated in the field and in the laboratory. Both selection of breeding sites by ovipositing females and differential survival of the larvae seem to be important. Unlike other species of Drosophila the domestic species do not seem to separate their feeding and breeding sites. D. immigrans, which frequently breeds in citrus fruits, was found to be particularly associated with these fruits when they were infected with the mould, Penicillium. Other species emerged more often from uninfected fruit. There may be a long standing evolutionary relationship between D. immigrans, citrus fruits and Penicillium. The body size of D. melanogaster, caught in traps, was found to change in a regular way during the season. This was partly an effect of temperature, but partly due to intraspecific competition at the highest population densities. Intraspecific competition is unimportant in the other species, though some species suffered from interspecific competition with D. melanogaster. The reproductive strategies of the seven Drosophila species were examined. They fell into two groups, large species with large clutches of small eggs, and small species with small clutches of large eggs. These strategies are not consistent with r— and K— selection theory, but may have been linked to the predictability of finding breeding sites. The ecology of domestic species of Drosophila was discussed with reference to current theories of population regulation.