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Climate-change has the potential to affect migratory birds by altering prey availability across their annual cycle. Observational and experimental approaches were used to understand the causes and consequences of these changes on the breeding productivity, mass regulation and survival of a wetland bird; the Eurasian reed warbler Acrocephalus scirpaceus. Climatic influences on wetland invertebrate populations were assessed by monitoring natural and experimentally-induced variations in temperature. Further increases in early spring temperatures are likely to result in earlier availability of prey resources. The responses of breeding birds to changes in their prey were tested with food supplementations, which advanced egg-laying dates, reduced the laying interval and incubation duration, and increased nestling growth rate. These effects enable earlier first fledglings and increase the opportunity for second breeding attempts within the peak invertebrate prey window. The consequences of prey availability on wintering body condition were tested by comparing resources and energy reserves in contrasting habitats in West Africa during the non-breeding period. Birds occupying prey-rich habitats maintained lower body reserves than conspecifics occupying prey-poor dry-scrub habitats, consistent with strategic buffering of reserves against starvation in food-poor habitat. These results suggest how reed warblers are able to survive in lower quality habitats and potentially avoid density-dependent mortality associated with drought as observed in other wetland migrants. Analysis of long term (>30 year) weather effects on survival revealed measurable but minor impacts, suggesting reed warblers are very adaptive to environmental change. Overall, this study provides strong support for climate-driven advance in spring invertebrate availability and identifies the reed warbler breeding and survival parameters most affected by increases to prey availability. This study provides an integrated and original understanding of the mechanisms which may underlie current levels of population growth in what appears to be one of the few long-distance migratory European songbird species currently benefiting from climate-change.

Rocky shore microphytobenthic biofilms are areas of high biodiversity, and are protected under UK and European Union legislation. Despite this, little is known about the photophysiology of these biofilms. This study aimed to provide a new contribution to microphytobenthic research with the addition of photophysiological knowledge focussing on the rocky intertidal to add to the extensive photophysiological research which has focussed on mudflats. More specifically the photoregulatory mechanisms of rocky shore biofilms had not been studied prior to this work. This study aimed to determine the effects of ambient environmental conditions, community structure and grazing on the photophysiology of the biofilms and elucidate the complex relationships between the abiotic and biotic factors which influence the biofilm. The community structure of the biofilm changed seasonally, with larger species (> 40 μm valve length and > 25 μm diameter) such as Parlibellus delognei being dominant during the winter months (December, January and February) and smaller ones (<40 μm valve length and < 25 μm diameter) such as Navicula bottnica during the spring months (March, April and May) indicating an environmental influence on the community structure of the biofilm. The biofilms were found to die-off (biomass below detection levels) in April and May and grow back in the November and December during a ‘reproductive phase’. An observed photophysiological ‘seasonality’ was primarily the result of the timing of the‘reproductive phase’ of the biofilm, with higher maximum relative electron transport rates (rETRmax) being recorded during November and December (on average 85 compared to 60 relative units), when these biofilms were growing after the spring die-off. High temperature and light dose had a negative effect on the rETRmax, particularly for biofilms on the upper shore sites. It was concluded that the combination of increased temperature and light dose, reducing rETRmax, and so productivity, and increased grazing contributed significantly to the spring dieoff with cells unable to replicate rapidly enough to compensate for increased grazing. By exposing biofilms to different temperatures ex-situ it was found that the lower shore biofilms ii were more resilient to high (> 25 °C) and low (< 10 °C) temperature with a smaller reduction in rETRmax, and ΔF/Fm’ observed in comparison to upper shore. Temperature was found to induce movement in the tube-forming upper shore species Navicula bottnica. This was likely to act as a secondary photoregulation strategy as it was found that high temperatures resulted in a reduced ability to induce non-photochemical quenching (NPQ). Biofilms were also treated with Latrunculin A (LAT-A) and DL- Dithiothreitol (DTT) in situ, and by comparing the photosynthetic patterns of response over an exposure period it was found that the upper shore biofilms utilised NPQ as the primary means of photoregulation whereas the lower shore biofilms utilised cell movement as the primary photoregulatory mechanisms. The upper and lower shore biofilms also utilised secondary mechanisms, migration in the upper shore samples, and NPQ in the lower shore samples, of downregulation, which allowed the cells to persist on the rocky shore where the rapid changes in environmental conditions result in a high stress environment. The overarching conclusion from this study is that rocky shore biofilms utilise a combination of photoregulatory mechanisms dependent upon life form in order to survive in an environment where many rapidly changing biotic and abiotic factors affect the community structure and photosynthesis of the biofilms.

The Imperial Dock Lock Special Protection Area (SPA) in Leith Docks on the Firth of Forth currently supports the largest common tern (Sterna hirundo) colony in Scotland. The nest site, a former lock wall in an operational port, was designated as an SPA for the species in 2004 but very little is known about the ecology of common terns in this man-made environment. This thesis examined their ecology using a combination of long-term data for the Firth of Forth region and field research at the colony. The dynamics of the Firth of Forth breeding population of common terns was linked both to local influences of predators and the regional status of their main food source, the Firth of Forth sprat stock. Colonisation of Leith Docks resulted from relocation of birds from natural islands in the Firth of Forth which were abandoned due to unsustainable levels of predation by gulls. Herring gulls (Larus argentatus) and lesser black-backed gulls (L. fuscus) are active predators in Leith Docks but at relatively low levels. Predation attempts by mink present a serious threat and could be highly detrimental to the colony. Foraging studies revealed that terns are feeding primarily in the Forth of Forth rather than within the docks, and that their diet consists mostly of sprat, but also sandeels and gadoids. The importance of sprat in the diet is discussed in relation to the potential reopening of the sprat fishery. Surveys of birds commuting between the colony and the feeding grounds showed that a range of flight lines are used but to different extents, and found no evidence of collisions with buildings or other man-made structures. Terns were well-habituated to regular human activity but were sensitive to unusual or high-level human disturbance factors. Gulls and crows, rather than humans, were the greatest disturbance factors for nesting birds overall. Currently the Imperial Dock Lock SPA is the only site in the region that could support common terns breeding in considerable numbers, and so the future of the Firth of Forth population of common terns is now dependent on this one site. There are a number of management options available, and the future persistence of the population relies on the continued monitoring of breeding numbers of terns, of predation levels and further assessment of the sprat stock.

O conceito de homologia similaridade entre partes com ancestralidade comum é um dos mais importantes conceitos dentro das análises evolutivas. Desde a sua origem, muitas definições que diferem na definição e na aplicação foram propostas. A presente dissertação tem como objetivo reconstruir a história da homologia para esclarecer teoricamente os debates modernos. Após esta historiografia, foi feita uma análise filomemética dos principais autores que discutiram a teoria e a prática do conceito. E, por último, foi feita uma discussão teórica do papel da homologia dentro da sistemática filogenética, abordando as principais discussões atuais. Os resultados demonstram que é possível esclarecer algumas discussões através da análise histórica do conceito sob a perspectiva da teoria da evolução. A análise filomemética reconstruiu os grupos de autores de acordo com suas escolas e propostas sobre a homologia. A análise teórica do conceito na metodologia filogenética evidencia que o conceito de homologia é equivalente ao conceito de sinapomorfia e uma nova visão sobre a relação de ausências, homoplasias e homologias é proposta. A discussão sobre as nomenclaturas e definição do conceito de homologia demonstra que as terminologias homologia primária e secundária são as melhores propostas para representar a relação da origem e legitimação de homólogos. Uma crítica às análises filomeméticas conceituais é feita. / The concept of homology similarity between parts due to common ancestrality is one of the most important concept in evolutionary analysis. Since it origin, many definitions which differ on definition and application were proposed. This dissertation has as the main goal reconstruct the history of homology to clarify theoretically the modern debates. After this historiography, was made a phylomemetic analysis of main authors that discussed the theory and pratics of homology concept. Lastly, was made a discussion on the importance of the role of homology in phylogenetic systematics, approaching actual discussions. The results support that is possible to clarify some discussions through historical analysis of this concept with an evolutionary background. The phylomemetic analysis reconstruct groups of author accordingly to their methodological schools and propositions. The historical analysis of the concept in phylogenetic analysis evidence that homology concept is equivalent to synapomorphy and a new look into the relation of absence, homoplasy and homology is proposed. The discussion on nomenclatures and definition of the concept of homology support that primary and secondary homology are the best proposition to represent the relation of origin and legitimation of homologs. A criticism to phylomemetic analysis is pointed.

Understanding what environmental factors influence species’ responses is crucial for adequate conservation management and prediction of responses to climate change. My study focused on a widespread aquatic migratory bird in Brazil; the Black Skimmer (Rynchops niger). Throughout the thesis I investigated the reliability of using photographs, citizen data, and visual observation to assess biological data such as moult score, occurrence, and identification of sexes. I also used stable isotopes and counts to assess changes in Black Skimmer’s resource use and abundance according to ENSO. I found photographs can be used to score moult in primary feathers, and that sexes in this species can be identified by visual observation from skins and photographs with Black Skimmer males being significantly larger than females. Using citizen photographs from nature enthusiasts web platforms, I found Black Skimmers moult during austral spring to summer in Brazil. Individuals select areas mostly in southern and southeastern Brazil to perform moult. Both sub-species (Amazonian and South American Black Skimmers) and sexes in Brazil selected estuaries while moulting yet coastal built-up areas could also be used. The South American Black Skimmers also selected more dunes and less mudflats than the Amazonian ones. There were differences in timing or duration of moult between sub-species or sexes with males taking more time and starting to moult earlier than females. I found Black Skimmers changed resource and had a higher diet input from estuarine habitats during the El Niño. Not only the foraging use during moult changed but also the abundance. The number of individuals overstaging (staying longer at the non-breeding site during the breeding season) at the study site was higher during the El Niño and lower during the La Niña than in regular years. Abundance was higher during eastern and northern winds but negatively affected by an interaction of temperature and ENSO. This study provided affordable non-invasive methods to studies in ornithology, fulfilled gaps in Black Skimmer’s life-history annual cycle, and was one of the first studies addressing how ENSO affects aquatic species in the South American Atlantic coast. Lessons learned from this study might underpin more effective conservation plans.

Despite that the life histories of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) are very well studied, there are still gaps in our knowledge which have consequences for management and conservation of these species. This is of particular importance now that wild populations of Atlantic salmon and anadromous brown trout are decreasing throughout their distribution range. This thesis aims to address some of these gaps in knowledge in life stage specific habitat use and mortality of these two species by bringing together five separate studies. Regular assessment of stock size is one of the most important aspects of fisheries management. Electrofishing techniques are widely used for the estimation of the size of stream dwelling fish populations for both fishery management and scientific study. In contrast to multiple pass, population depletion methods, single pass catch-per-unit-effort (CPUE) methods are less time consuming and labour intensive. A possible issue with the commonly used, fixed total time CPUE protocol is that it does not differentiate between the time spent actively fishing and the time incurred while not actively fishing, leading to handling error which is likely related to fish density. This was tested in a comparative field study. I showed that this commonly used technique is systematically underestimating juvenile salmonid numbers at higher densities. In addition this technique is failing to adequately determine fish community structure at low population densities. This work indicates a simple modification to the methodology that will reduce systematic error. Knowledge of the species’ biology and habitat requirements can be linked with habitat data to create a model that predicts the distribution of that species. As salmonids, such as Atlantic salmon, have fairly strict habitat requirements, knowledge of habitat use by salmon can then be used to estimate the potential salmonid production in a given area of certain quality. The accuracy of a habitat grading system currently used by the Loughs Agency was tested. The results suggest that in its current format, the habitat grading system does not accurately describe the abundance of juvenile salmonids. When data was analysed to see which habitat variables best described salmonid density, for 0+ salmon important variables were flow and substrate and for older juveniles the important variables were flow, substrate, depth and percentage of undercut banks. All populations are controlled by density-dependent and density –independent factors. For a species such as Atlantic salmon that has life stages differing in habitat requirements, the relative contributions of these two factors for population regulation on each life stage are likely to vary. Using a long-term data-set on Atlantic salmon migrants returning to the Foyle catchment, Ireland, the role of density-dependent and life-stage specific environmental factors regulating population size was determined. A Ricker density-dependent model showed that the spawning adult population size significantly predicted variation in the resultant filial generation, however a large amount of variation remained unexplained. It was shown that environmental factors were significant in explaining some of the remaining variance and that these influences were linked to specific life stages. Three life stages – spawning and incubation, fry emergence, and marine survival – were shown to be sensitive to environmental effects resulting in changes to the returning cohort strength. It is concluded that these life stage specific environmental effects are likely to contribute to the stochastic variation in population size resulting from the application of traditional stock-recruitment models. Atlantic salmon undertake extensive migrations between freshwater and marine habitats. Smolt migration is associated with high mortality and is thus considered a critical life stage in the Atlantic salmon life history. Smolt migration through standing waters is still mostly an unknown process and it is not known what guides migration during lake migration. Using acoustic telemetry, three hypotheses derived from known principles of migration in rivers were tested: i.) smolts will take the shortest possible route, ii.) smolts will display unidirectional movement and iii.) smolts will be continuously moving. None of these three expectations were supported by the results of this study. Instead evidence was found of smolts moving in a seemingly random fashion, displaying counter intuitive migration patterns and spending relatively long periods effectively static during their lake migration. Brown trout display a great range of life history variation ranging from river residency to anadromy. Unlike Atlantic salmon that migrate hundreds of kilometres to the open ocean to feed, anadromous brown trout often stay within 80-100 km from their natal river in coastal areas. Despite this, very little is still known about their behaviour during this coastal feeding part of the life cycle. It was found that brown trout in the Clyde estuary use a fairly small part of the estuary and seem to move fairly actively. Fish size did not explain any of the movement or residency patterns. The five separate studies presented in this thesis combine field empirical studies from rivers, lakes and the coastal marine environments and historical data analysis studies on two salmonid species. The results presented in this thesis provide tools for managers of anadromous salmonids.

Collective movements are ubiquitous in biological systems, occurring at all scales; from the sub-organismal movements of groups of cells, to the far-ranging movements of bird flocks and herds of large herbivores. Movement patterns at these vastly different scales often exhibit surprisingly similar patterns, suggesting that mathematically similar mechanisms may drive collective movements across many systems. The aims of this study were three-fold. First, to develop mechanistic movement models capable of producing the observed wealth of spatial patterns. Second, to tailor statistical inference approaches to these models that are capable of identifying drivers of collective movement that could be applied to a wide range of study systems. Third, to validate the approaches by fitting the mechanistic models to data from diverse biological systems. These study systems included two small-scale in vitro cellular systems, involving movement of groups of human melanoma cells and Dictyostelium discoideum (slime mould) cells, and a third much larger-scale system, involving wildebeest in the Serengeti ecosystem. I developed a series of mechanistic movement models, based on advection-diffusion partial differential equations and integro-differential equations, that describe changes in the spatio-temporal distribution of the study population as a consequence of various movement drivers, including environmental gradients, environmental depletion, social behaviour, and spatial and temporal heterogeneity in the response of the individuals to these drivers. I also developed a number of approaches to statistical inference (comprising both parameter estimation and model comparison) for these models that ranged from frequentist, to pseudo-Bayesian, to fully Bayesian. These inference approaches also varied in whether they required numerical solutions of the models, or whether the need for numerical solutions was bypassed by using gradient matching methods. The inference methods were specifically designed to be effective in the face of the many difficulties presented by advection-diffusion models, particularly high computational costs and instabilities in numerical model solutions, which have previously prevented these models from being fitted to data. It was also necessary for these inference methods to be able to cope with data of different qualities; the cellular data provided accurate information on the locations of all individuals through time, while the wildebeest data consisted of coarse ordinal abundance categories on a spatial grid at monthly intervals. By applying the developed models and inference methods to data from each study system, I drew a number of conclusions about the mechanisms driving movement in these systems. In all three systems, for example, there was evidence of a saturating response to an environmental gradient in a resource or chemical attractant that the individuals could deplete locally. I also found evidence of temporal dependence in the movement parameters for all systems. This indicates that the simplifying assumption that behaviour is constant, which has been made by many previous studies that have modelled movement, is unlikely to be justified. Differences between the systems were also demonstrated, such as overcrowding affecting the movements of melanoma and wildebeest, but not Dictyostelium, and wildebeest having a much greater range of perception than cells, and thus being able to respond to environmental conditions tens of kilometres away. The toolbox of methods developed in this thesis could be applied to increase understanding of the mechanisms underlying collective movement in a wide range of systems. In their current form, these methods are capable of producing very close matches between models and data for our simple cell systems, and also produce a relatively good model fit in the more complex wildebeest system, where there is, however, still some room for improvement. While more work is required to make the models generalisable to all taxa, particularly through the addition of memory-driven movement, inter-individual differences in behaviour, and more complex social dynamics, the advection-diffusion modelling framework is flexible enough for these additional behaviours to be incorporated in the future. A greater understanding of what drives collective movements in different systems could allow management of these movements to prevent the collapse of important migrations, control pest species, or prevent the spread of cancer.