http://www.dspace.cam.ac.uk:80/handle/1810/219489 Mon, 20 May 2013 17:11:11 GMT 2013-05-20T17:11:11Z http://www.dspace.cam.ac.uk:80/handle/1810/244307 Title: The biostratigraphy, palaeoecology and geochemistry of a long lacustrine sequence from NW Greece Authors: Frogley, Michael Reginald Abstract: Examination of an important new 319m core of lake sediment recovered from Ioannina in NW Greece has attempted to relate changes in the lake to variations in the regional climate of south-central Europe over the last 600,000 years. The site is known to have been extremely sensitive to past climatic change for three reasons: (i) temperate vegetation persisted throughout glacial stages (albeit at low frequencies), so the vegetational response to climatic change would therefore have been almost immediate; (ii) the extreme thickness of the sediments suggests that accumulation rates were high (at times, > 1m per thousand years), which has enabled high-resolution palaeoclimatic reconstructions; and (iii) precipitation of authigenic carbonate has preserved a remarkably sensitive proxy record of productivity variations for most of the lake's history. Well-defined shifts from glacial - interglacial mode have been correlated with vegetational changes identified in a core previously analysed from the same basin (using magnetic susceptibility profiles), enabling tentative correlations to be suggested with other European terrestrial sequences and with the marine oxygen isotope record, back to marine isotope stage 16. Twelve AMS radiocarbon determinations from the upper part of the core, together with the identification of a series of reversed palaeomagnetic events within the Brunhes chron, support the proposed age model for the sequence. The sediments at Ioannina, unlike most of the other long terrestrial European sequences, are calcareous and contain mollusc and ostracod assemblages. Part of this project has involved a comprehensive review of Quaternary and modem aquatic faunas from the lake, as well as the description, illustration and critical assessment of several poorly-known endemic taxa. Faunal assemblage data have been used to provide valuable information concerning the variable response of lake-level to climatic change over time. Convincing new mollusc an evidence indicates low lake-levels at the Last Glacial Maximum, agreeing with regional pollen data, but conflicting with geomorphological evidence derived from Kastritsa, a well-documented nearby Palaeolithic cave site. It is suggested that this discrepancy may be a result of subsequent tectonic uplift of the rockshelter. In addition, stable isotopic analyses of both the ostracods and the bulk carbonate within the sediments have contributed towards deriving a comprehensive palaeoenvironmental history for the site. Although the study analysed physical, biological and geochemical aspects of the entire core, two distinct parts of the record were selected for more detailed investigation. High-resolution analysis over the last interglacial (the Eemian) has revealed evidence for a clear, two-step deglaciation at the beginning of the period, known from elsewhere as the Zeifen-Kattegat Oscillation. Climatic instability has also been detected within the full interglacial. Comparisons are drawn with a range of other Eemian records from across Europe, as well as the Greenland ice cores. High-resolution analysis of the period from the end of the last glacial to the present day has also revealed evidence for climatic instability. A cool and arid oscillation is demonstrated by several climatic proxies that may constitute the first recognition of the Younger Dryas stadial from Greece. A shorter, but more subdued cooling event has also been detected during the first half of the Holocene, which may correspond with a widespread climatic oscillation from high-resolution terrestrial, marine and ice core records that has been dated to between 7,500 and 8,000 years BP. Thu, 01 Jan 1998 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/244307 1998-01-01T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/243405 Title: Extraterritorial prospecting and territory defence in cooperatively breeding meerkats Authors: Mares, Rafael Abstract: In group living animals where natal dispersal is delayed, prospecting allows individuals to asses their future dispersal and breeding opportunities and, in males of some species, may minimize the costs of delaying dispersal by enabling extra-group breeding while still resident in the natal group. While evidence of prospecting is widespread, comparatively little is known about the development of this behaviour and few studies have investigated the factors that may affect investment in prospecting, as it is typically difficult to monitor such mobile individuals. Prospectors typically encounter neighbouring groups during extraterritorial forays and resident individuals in these groups respond aggressively to approaches by extra- group males, given the potential loss in direct and indirect fitness that prospectors may inflict. As with prospecting behaviour, few studies have investigated the causes of individual differences in investment in repelling prospectors and measured the costs of such territory defence. In this dissertation, I exploit our ability to closely monitor prospecting males in meerkats, to investigate the causes of individual variation in extraterritorial prospecting effort and aggressive responses to prospector intrusions. In Chapter 3, I show that, as adults, heavier males invest more in prospecting than lighter ones, and that males time their forays in order to maximize their chances of dispersal, while minimizing the associated costs by prospecting when neighbouring groups are in close proximity to their own. In Chapter 4, I demonstrate that males that are heavier in early life start prospecting at a younger age and contribute less to helping later in life, than lighter males. In Chapter 5, I show that the threats posed by prospectors towards residents are associated with high investment by resident males in repelling intruders, which has measurable costs in terms of weight gain and cooperative contributions to offspring care. Finally, in Chapter 6, the experimental presentation of scent cues reveals that meerkats discriminate between resident and extra-group male scent cues, and that resident dominant males exhibit stronger responses to indirect evidence of prospectors than other group members. Tue, 06 Mar 2012 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243405 2012-03-06T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/243353 Title: The evolutionary genetics of sexually selected plumage colour traits in the galliform birds Authors: Nadeau, Nicola Jacqueline Abstract: Extravagant male plumage traits in birds are a classic example of sexual selection. However we know very little about the units that selection is acting upon, the genes themselves – what are they and how are they influenced by sexual selection? In this study I focused on in the evolution and genetics of colouration the galliform birds. Several novel loci were used to create a well resolved phylogeny of this group. This was then used to investigate and reconstruct the evolution of sexual plumage dichromatism. Four pigmentation genes were sequenced in an array of galliform species. A measure of the rate of evolutionary change (dN/dS) at these loci was then compared between lineages with different strengths of sexual selection, using sexual dichromatism as the main index of sexual selection. I found evidence for sexual selection acting at the MC1R locus, in the form of a robust correlation between dN/dS and sexual plumage dichromatism that was not found at any of the other loci. I then went on to investigate the evolution and population genetics of MC1R in the grouse, focusing on the strongly dichromatic black grouse and the relatively monochromatic red grouse. I found some evidence for an adaptive change at this locus between these species. Finally I used a candidate gene approach to investigate the role of several genes in avian pigmentation using the Japanese quail (Coturnix japonica) as a model system. I found evidence that the avian agouti gene is involved in dorso-ventral pigmentation patterning and a regulatory mutation at this locus that produces a yellow phenotype. In addition point mutations at MC1R and TYRP1 were found to be responsible for producing pigmentation variants. I then compared the expression of several of these candidate genes in male and female common pheasants (Phasianus colchicus) and found lower TYRP1 expression in males. Knowledge of the genetic basis of secondary sexual traits and the action of sexual selection at this level could have important implications for our understanding of the process of sexual selection as a whole. Tue, 16 Jan 2007 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243353 2007-01-16T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/241413 Title: Appendage development and early Distal-less regulation in arthropods: A study of the chelicerate Tetranychus urticae (Acarida) Authors: Cyrus-Kent, Chloë Abstract: A major goal of evolutionary developmental biology is to explore mechanisms and events underlying evolution of the myriad body plan morphologies expressed both genetically and phenotypically within the animal kingdom. Arthropods exhibit an astounding array of morphological diversity both within and between representative sub-phyla, thus providing an ideal phylum through which to address questions of body plan innovation and diversification. Major arthropod groups are recognised and defined by the distinct form and number of articulated appendages present along the antero-posterior axis of their segmented bodies. A great deal is known about the developmental genetics of limb development in the model insect Drosophila melanogaster, added to which, much comparative gene expression data and a growing body of functional genetic data is emerging for other arthropod species. Arthropod limb primordia are consistently marked by expression of the homeobox gene Distal-less (Dll), and the focus of this thesis is to compare signalling mediated by early Dll regulatory genes activity along antero-posterior and dorso-ventral embryonic axes during limb specification in Drosophila, with the activity of their orthologs in the widely disparate chelicerate, the spider mite Tetranychus urticae – interpreting new data with that available for other arthropods. Having made a detailed study of spider mite embryonic (and post-embryonic) development, to provide a basis for understanding mRNA transcription and protein activity patterns, I confirmed typical expression of Tetranychus Dll in prosomal limb primordia. I obtained limited results for the candidate antero-posterior positioning genes wingless and engrailed, although one of the two engrailed paralogs I identified is reportedly expressed in posterior segmental compartments, consistent with possible conservation of Engrailed-Wingless interactions in metameric patterning and positive regulation of Dll in arthropod limb specification. In Drosophila, wingless-dependent Dll transcription is restricted along the dorso-ventral axis by dorsal Dpp-mediated and ventral EGFR-mediated signalling gradients. Based on data from Tetranychus and other arthropods, neither dorsal nor ventral signalling regimes appear conserved outside the Drosophila system. Dll suppression in fly abdominal segments occurs due to powerful Hox (Ubx/AbdA) repression of the early Dll cis-regulatory element; this is discussed in relation to the independently evolved limbless chelicerate opisthosoma, informed by hypothetical scenarios of cis (regulatory DNA) and trans (coding sequence) evolution. Given practical difficulties and limitations encountered while working with spider mites, I offer a final assessment of the place of Tetranychus urticae as a non-model, and yet still valuable chelicerate species to consider carrying into the exciting future of evolutionary developmental biology. Sat, 08 Dec 2007 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/241413 2007-12-08T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/228687 Title: DNA damage responses in the context of the cell division cycle Authors: Giunta, Simona Abstract: During my PhD, I have investigated aspects of the DNA damage response (DDR) in the context of three different cellular scenarios: DNA damage signalling in response to double-strand breaks during mitosis, coordination of DNA replication with DNA damage responses by regulation of the GINS complex, and checkpoint activation by the prototypical checkpoint protein Rad9. Here, I show that mitotic cells treated with DNA break-inducing agents activate a ‘primary’ DDR, including ATM and DNA-PK-dependent H2AX phosphorylation and recruitment of MDC1 and the MRN complex to damage sites. However, downstream DDR events and induction of a DNA damage checkpoint are inhibited in mitosis, with full DDR activation only ensuing when damaged mitotic cells enter G1. In addition, I provide evidence that induction of a primary DDR in mitosis is biologically important for cell viability. The GINS complex is an evolutionarily conserved component of the DNA replication machinery and may represent an ideal candidate for transferring the DNA damage signal to the replication apparatus. Here, I show the identification of a consensus ‘SQ’ PIKK phosphorylation motif at the carboxyl end of the GINS complex subunit, Psf1. In Saccharomyces cerevisiae, switching the conserved serine to a glutamic acid is lethal, indicating that the site is crucial for the protein’s function. Moreover, in human cells, I identified UV-DDB, a heterodimeric complex involved in NER repair, as a binding partner that specifically interacts with the Psf1 C-terminus in vitro. Finally, I discuss my findings in characterizing functional interactions between Rad9 and Chk1 in S. cerevisiae. I show that specific consensus CDK sites within Rad9 N-terminus are essential to enable Chk1 phosphorylation and activation, and that MCPH1, a human homologue of Rad9, may share a conserved function in binding and activating Chk1, underscoring the evolutionarily conservation of checkpoint activation mechanisms. Description: Pagination different from approved bound copy, but content the same. Tue, 16 Nov 2010 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/228687 2010-11-16T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/226862 Title: Biomechanics of the fibrillar adhesive system in insects Authors: Bullock, James Michael Rex Abstract: Many animals are able to scale smooth surfaces using adhesive structures on their feet. These organs are either soft pads with a relatively smooth surface or dense arrays of microscopic adhesive hairs with both designs having independently evolved in diverse taxa of arthropods and vertebrates. Biological adhesive pads out-perform conventional adhesives in many respects, making them important models for biomimetics. Hairy pads have attracted particular attention, because it has become feasible to fabricate similar synthetic microstructures. Nevertheless, the detailed performance and functional properties have not been characterised for any natural fibrillar adhesive system, and many fundamental aspects are still not understood. The aim of this thesis was therefore to investigate the fibrillar adhesive system of leaf beetles as a model. To investigate the functional implications of hairy pad design, the attachment performance between hairy pads of the leaf beetle Gastrophysa viridula and smooth pads of stick insects (Carausius morosus) was compared. Adhesive and frictional stresses were found to be similar in smooth and hairy pads, inconsistent with contact splitting theory, which predicts higher adhesive stresses for fibrillar adhesives. Hairy pads showed a greater direction-dependence of friction forces than smooth pads, confirming the importance of the asymmetric design of individual setae for effortless detachment. Experiments with contaminating particles also showed that hairy pads removed contamination more rapidly and efficiently than smooth pads. Self-cleaning ability had not been previously documented for adhesive organs of insects. To investigate to what extent the hairy system is able to compensate for surface roughness, whole-body attachment forces were measured for varying roughness levels. Attachment was reduced for all length scales of surface roughness, but in particular for asperity sizes smaller than the diameter of individual seta tips. Leaf beetles possess adhesive pads on three tarsal segments, which vary in setal morphology. However, the functional implications of this variation are unknown. The mechanical and adhesive properties of individual pads were therefore tested and their use during climbing observed. Proximal pads were shown to be stiffer than distal pads, conferring stability during pushing. In contrast, the softer distal pads allowed better attachment to rough surfaces. Hence the morphological variation is explained by an effective division of labour between the pads. To investigate an extreme example of pushing in a hairy system, pad use was studied during jumping in flea beetles. The pushing forces needed during take-off were exclusively produced by the proximal pads, again confirming the division of labour. To characterise the effects of different hair morphologies and to understand how individual setae contribute to array and whole-animal performance, single hair forces were measured using a glass capillary cantilever. Male-specific discoidal hairs were shown to be both stiffer and more adhesive than pointed and spatula-tipped setae, likely affecting overall pad stability and attachment. This thesis has shown that hairy pads are similar to smooth pads in the magnitude of adhesive stress supported yet outperform them in detachability and self-cleaning. It was also demonstrated that there are considerable differences in design and performance even within setal arrays of the same insect, indicating the limitations of general models of fibrillar adhesion and underlining the importance of specialised adaptations. Mon, 11 Oct 2010 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/226862 2010-10-11T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/226742 Title: Socialiy, social learning and individual differences in rooks, jackdaws and Eurasian jays Authors: Federspiel, Ira Gil Abstract: Social intelligence is thought to have evolved as an adaptation to the complex situations group-living animals encounter in their daily lives. High levels of sociality provide individuals with opportunities to learn from one another. Social learning provides individuals with a relatively cheap and quick alternative to individual learning. This thesis investigated social learning in three corvid species: gregarious rooks (Corvus frugilegus) and jackdaws (Corvus monedula) and nongregarious, territorial Eurasian jays (Garrulus glandarius). In addition to that, the species' social structure was analysed and individual differences between members of each species were determined. Introducing the field of social learning research, I presented a new framework for investigating social learning, combining ecology, ethology and evolution. Experiments were conducted within that framework. I found that rooks and jackdaws develop social bonds and dominance hierarchies, whereas Eurasian jays do not. This is most likely related to their territoriality. In two experiments using two-action tasks, jackdaws learned socially. The underlying social learning mechanism was enhancement, which fits in with their feeding ecology. Rooks did not show social learning when presented with videos of conspecifics opening an apparatus. This might have been due to the difficulty of transferring information from videos or due to an ingrained 'affinity' to innovation and/or rapid trial-and-error learning overriding social learning processes. Individual differences along the bold/shy axis existed in all three species, but they were not stable across contexts. Thus, it seemed that the individuals perceived the two seemingly similar contexts that were designed to investigate neophobia and exploration (novel object in familiar environment; novel environment) as two different situations. The information may therefore have been processed by two distinct underlying mechanisms, which elicited different responses in each of the contexts. The implications of the findings of this thesis are discussed with regard to the new framework, integrating sociality, social learning and individual differences with the species' ecology. Mon, 07 Jun 2010 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/226742 2010-06-07T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/225237 Title: The ecology and conservation of the white-winged nightjar Caprimulgus candicans Authors: Pople, Robert Grant Abstract: In the tradition of previous studies of threatened species, this thesis was undertaken with the aim of improving our understanding of the ecology of the White-winged Nightjar Caprimulgus candicans, and providing the information necessary to facilitate conservation efforts on its behalf. In 1998–2001, I studied a population of White-winged Nightjars at Aguará Ñu, an area of cerrado habitats within the Reserva Natural del Bosque Mbaracayú, eastern Paraguay. Over the course of three fieldwork seasons, I captured and ringed a total of 49 nightjars (34 adults and 15 young birds). Young females first bred at approximately one year old, while still in pre-definitive plumage. Young males exhibited a form of delayed plumage maturation, whereby they only attained definitive plumage following a prolonged moult spanning much of their first potential breeding season. No evidence was obtained to suggest that they succeeded in breeding while in this conspicuously intermediate state of moult. Considerable variation was noted in the plumage whiteness of definitive males, but no clear evidence was found for consistent age-related increases in white. During the breeding season, males defended small aggregated display territories, at which they conducted nuptial display flights between late August and early January. Female nightjars were responsible for all the parental care, and apparently visited male display arenas solely to obtain copulations. Chick paternity data confirmed that the study population was polygynous, with patterns of male aggregation suggestive of an exploded lek or ‘landmark’ mating system. Radio-telemetry studies showed that nightjars utilised home ranges of at least 20 to 40 hectares during the eight to ten months for which they were monitored. Home ranges contained a disproportionately large amount of young campo cerrado vegetation, but no forest or old campo cerrado habitats. When selecting foraging sites within their ranges, nightjars preferred younger and avoided older campo cerrado vegetation; wet grassland was utilised roughly in proportion to its availability. Observed patterns of habitat selection were potentially explained by the greater abundance of insect prey in younger habitats. When selecting daytime roost sites, nightjars preferred vegetation of intermediate age, reflecting their need for a balance between cover and ease of access. A more general analysis of patterns of sexual dimorphism within the Caprimulgidae showed that, although almost 80% of nightjar species exhibit some dimorphism of plumage whiteness, the study species was by far the most extreme case. The striking plumage of the male was partly explained by a strong positive relationship between wing white and openness of breeding habitats within the family. However, this failed to explain the complete absence of white in the female plumage, or the extent of white dimorphism shown by the species. The most likely explanation would appear to be that extreme plumage dimorphism occurred in conjunction with the evolution of polygyny and female-only care in this open-country species. The implications of these findings for the conservation of the White-winged Nightjar are highlighted, and recommendations are proposed for future work and conservation action. Mon, 06 Oct 2003 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/225237 2003-10-06T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/225183 Title: Individual variation in cooperative behaviour in meerkats Authors: English, Sinéad Abstract: Individual variation in cooperation is a striking yet poorly understood feature of many animal societies, particularly in cooperative breeders where individuals assist in the care of young that are not their own. While previous research on these systems has emphasised the plasticity of helping and how it varies with current environmental and social conditions, in this dissertation I examine how individual variation is constrained and influenced by trade-offs with other behaviours and experiences in early life. I demonstrate that variation in cooperative pup care (babysitting and provisioning) is consistent within individuals over time (Chapter 3). Provisioning is more consistent than babysitting, although the two behaviours are highly correlated within individuals. I then focus on the variation in helping that remains once current factors, such as condition, group size and food availability, are taken into account. In Chapter 4, I explore the possibility that variation in helping can be explained by personality, or consistency in behavioural traits such as exploration or risk-taking. I find little evidence for consistent individual differences in field measures of personality traits, however, with such behaviours instead being group-specific. Early social experiences are known to have important and lasting effects on later fitness and behaviour: in Chapter 5, I demonstrate that, in female meerkats only, growing up in a group with more helpers is correlated with reduced cooperation later in life. This result suggests the importance of future fitness in influencing current cooperative behaviour, as females raised in larger groups are more likely to attain dominance. Finally, I examine the extent to which vocal communication between carers and young is influenced by variation in contributions to cooperation. Females are more sensitive to increased begging rate (Chapter 6), which reflects general sex differences in cooperative behaviour. Carers modify their vocalizations but not their foraging behaviour in the presence of pups, and the way in which they vocalize during provisioning events suggests these calls serve to increase efficiency of prey transfer (Chapter 7). Mon, 12 Apr 2010 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/225183 2010-04-12T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/220933 Title: Neural basis of a visuo-motor transformation in the fly Authors: Huston, Stephen Abstract: How the outputs of populations of sensory neurons are used by motor systems to generate appropriate behaviour is a long standing question in neuroscience. I address this problem by studying a comparatively simple model system. In the fly, Neck Motor Neurons control gaze-stabilising head movements that occur during wholebody rotations. These motor neurons receive several sensory inputs including one from well-characterized visual interneurons, Tangential Cells (TCs), which respond to panoramic image shifts induced during self-motion. In chapter one, I provide a general introduction to sensory-motor circuits and the fly gaze-stabilisation system. In chapter two, I report that the visual receptive fields of Neck Motor Neurons are similar to those of the TCs. Using this result, I show an alignment between the coordinate systems used by the visual and the neck motor systems to process visual information. Thus, TCs encode visual inputs in a manner already closely matched to the requirements of the neck motor neurons, considerably facilitating the visual-motor transformation In chapter three, I analyse the gating of neck motor neuron visual responses by convergent mechanosensory inputs from the halteres. Some neck motor neurons do not fire action potentials in response to visual stimuli alone, but they will in response to haltere movements. I show that visual stimuli produce sustained sub-threshold depolarisations in these neurons. These visual depolarisations increase the proportion of haltere-induced action potentials in neck motor neurons. Thus, visual inputs can only affect the spiking output if the halteres are moving. This simple mechanism could explain why flies only make visually induced head movements during walking or flight: behaviours that involve beating the halteres. By analysing how the outputs of a model sensory system are used, I have shown a novel alignment between sensory and motor neuron populations and a simple mechanism underlying multisensory fusion. Tue, 17 Jan 2006 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/220933 2006-01-17T00:00:00Z