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Understanding dispersal is of prime importance in conservation and population biology. Individual traits related to motion and navigation during dispersal may differ: (1) among species differing in habitat distribution, which in turn, may lead to interspecific differences in the potential for and costs of dispersal, (2) among populations of a species that experiences different levels of habitat fragmentation; (3) among individuals differing in their dispersal strategy and (4) between the sexes due to sexual differences in behaviour and dispersal tendencies. In butterflies, the visual system plays a central role in dispersal, but exactly how the visual system is related to dispersal has received far less attention than flight morphology. We studied two butterfly species to explore the relationships between flight and eye morphology, and dispersal. We predicted interspecific, intraspecific and intersexual differences for both flight and eye morphology relative to i) species-specific habitat distribution, ii) variation in dispersal strategy within each species and iii) behavioural differences between sexes. However, we did not investigate for potential population differences. We found: (1) sexual differences that presumably reflect different demands on both male and female visual and flight systems, (2) a higher wing loading (i.e. a proxy for flight performance), larger eyes and larger facet sizes in the frontal and lateral region of the eye (i.e. better navigation capacities) in the species inhabiting naturally fragmented habitat compared to the species inhabiting rather continuous habitat, and (3) larger facets in the frontal region in dispersers compared to residents within a species. Hence, dispersers may have similar locomotory capacity but potentially better navigation capacity. Dispersal ecology and evolution have attracted much attention, but there are still significant gaps in our understanding of the mechanisms of dispersal. Unfortunately, for many species we

While the majority of bioluminescent pelagic organisms emit blue light, some transparent planktonic annelids (Tomopteridae) have been found to emit yellow light from parapodial glands (rosette and hyaline). Since long wavelengths have a weak propagation coefficient and appear to be imperceptible to most midwater species, this bioluminescence is commonly thought to act as a private communication channel. This work aims to explore this functional hypothesis through a multidisciplinary approach of bioluminescence in Tomopteris helgolandica as main model species and in four related species: T. carpenteri, T. pacifica, T. planktonis and T. septentrionalis. The structural homology between the rosette of the tail-bearing species and the hyaline glands of the tail-less species is evidenced, suggesting that both gland types evolved from a common light-emitting structure and differentiated along a functional and migrational axis extending from endocrine secretion close to the coelomic ramus to exocrine secretion close to the lateral margin of the pinna. In T. helgolandica, bioluminescence is triggered by the activation of nicotinic cholinergic receptors and a Ca2+-dependent mechanism involving L-type volgate-gated channels. Despite significant differences in their light emission patterns, cholinergic control is also suggested in T. planktonis. Indeed, an unexpected diversity in emission patterns is highlighted including yellow and blue, intra- and extraglandular displays. Consequently, the ecological advantage provided by this bioluminescence could be more diverse than originally suspected. Although the first behavioural approach of light perception by T. helgolandica tends to support the hypothesis of intraspecific communication, the possibility of a defensive use of bioluminescence should remain an open question., (SC - Sciences) -- UCL, 2016

Ecuadorian farmers often cultivate potatoes under high-input systems with the subsequent risks for the environment and farmer’s health. An alternative to reduce the use of agrochemicals is by applying beneficial soil microorganisms such as arbuscular mycorrhizal fungi (AMF) and Plant Growth Promoting Rhizobacteria (PGPR). However, the PGPR and AMF interactions have been little explored in order to formulate efficient consortia-based inoculants. A preliminary field experiment showed that inoculation of potato with commercial AMF products did not improve tuber yield likely due to scarce establishment of the AMF. Hence, in the present study we aimed to: (1) evaluate the interactions between AMF and several PGPR when co-entrapped in alginate beads in order to increase the root colonization of the AMF in potato plants; (2) assess the effect of co-inoculation of AMF and PGPR on the elicitation of induced systemic resistance of potato plants and (3) evaluate the effect of crude extracts produced by two PGPR on the root colonization of potato by one AMF. Our results showed that a suitable AMF-PGPR combination could improve the AMF root colonization of potato. Further, PGPR-AMF co-inoculation of potato plants led to an activation of the plant systemic defense system via ethylene response factor 3 (ERF3) in presence of the fungal pathogen Rhizoctonia solani. Finally, the development of the AMF was stimulated by crude extracts produced by one PGPR isolate. Co-inoculation/co-entrapment of suitable AMF-PGPR combinations can promote the root colonization by the AMF and the activation of plant defense system; this effect can be enhanced by the addition of certain PGPR metabolites. Encapsulation technology may represent an innovative method to formulate efficient consortia-based inoculants for potato cropping., (AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 2016

Climate warming affects the rate and timing of the development in ectothermic organisms. Short-living, ectothermic organisms (including many insects) showing thermal plasticity in life-cycle regulation could, for example, increase the number of generations per year under warmer conditions. However, changed phenology may challenge the way organisms in temperate climates deal with the available thermal time window at the end of summer. Although adaptive plasticity is widely assumed in multivoltine organisms, rapid environmental change could distort the quality of information given by environmental cues that organisms use to make developmental decisions. Developmental traps are scenarios in which rapid environmental change triggers organisms to pursue maladaptive developmental pathways. This occurs because organisms must rely upon current environmental cues to predict future environmental conditions and corresponds to a novel case of ecological or evolutionary traps. Examples of introduced, invasive species are congruent with this hypothesis. Based on preliminary experiments, we argue that the dramatic declines of the Wall Brown (Lasiommata megera) in NW Europe may be an example of a developmental trap. This formerly widespread, bivoltine (or even multivoltine) butterfly has become a conundrum to conservationist biologists. A split-brood field experiment with L. megera indeed suggests issues with life-cycle regulation decisions at the end of summer. In areas where the species went extinct recently, 100% of the individuals developed directly into a third generation without larval diapause, whereas only 42.5% did so in the areas where the species still occurs. Under unfavourable autumn conditions, the attempted third generation will result in high mortality and eventually a lost or ‘suicidal’ third generation in this insect with non-overlapping, discrete generations. We discuss the idea of a developmental trap within an integrated framework for assessing the vulnerabilit

We assessed the state of knowledge regarding the effects of large-scale pollution with neonicotinoid insecticides and fipronil on non-target invertebrate species of terrestrial, freshwater and marine environments. A large section of the assessment is dedicated to the state of knowledge on sublethal effects on honeybees (Apis mellifera) because this important pollinator is the most studied non-target invertebrate species. Lepidoptera (butterflies and moths), Lumbricidae (earthworms), Apoidae sensu lato (bumblebees, solitary bees) and the section “other invertebrates” review available studies on the other terrestrial species. The sections on freshwater and marine species are rather short as little is known so far about the impact of neonicotinoid insecticides and fipronil on the diverse invertebrate fauna of these widely exposed habitats. For terrestrial and aquatic invertebrate species, the known effects of neonicotinoid pesticides and fipronil are described ranging from organismal toxicology and behavioural effects to population-level effects. For earthworms, freshwater and marine species, the relation of findings to regulatory risk assessment is described. Neonicotinoid insecticides exhibit very high toxicity to a wide range of invertebrates, particularly insects, and field-realistic exposure is likely to result in both lethal and a broad range of important sublethal impacts. There is a major knowledge gap regarding impacts on the grand majority of invertebrates, many of which perform essential roles enabling healthy ecosystem functioning. The data on the few non-target species on which field tests have been performed are limited by major flaws in the outdated test protocols. Despite large knowledge gaps and uncertainties, enough knowledge exists to conclude that existing levels of pollution with neonicotinoids and fipronil resulting from presently authorized uses frequently exceed the lowest observed adverse effect concentrations and are thus likely to have large

Recent anthropogenic eutrophication has meant that host plants of nettle-feeding insects became quasi-omnipresent in fertile regions of Western Europe. However, host plant resource quality – in terms of microclimate and nutritional value – may vary considerably between the ‘original’ forest habitat and ‘recent’ agricul- tural habitat. Here, we compared development in both environmental settings using a split-brood design, so as to explore to what extent larval survival and adult morphology in the nettle-feeding butterfly Aglais urticae are influenced by the anthropogenic environment. Nettles along field margins had higher C/N ratios and provided warmer microclimates to larvae. Larvae developed 20% faster and tended to improve their survival rates, on the agricultural land compared to woodland. Our split-brood approach indicated plastic responses within families, but also family effects in the phenotypic responses. Adult males and females had darker wing pigmentation in the drier and warmer agricultural environment, which contrasts with the thermal melanism hypothesis. Developmental plasticity in response to this microclimatically different and more variable habitat was asso- ciated with a broader phenotypic parameter space for the species. Both habitat expansion and developmental plasticity are likely contributors to the ecological and evolutionary success of these nettle-feeding insects in anthropogenic environments under high nitrogen load.

Understanding the speciation process usually involves the study of the geographic and ecological factors influencing reproductive isolation, as well as the action of evolutionary forces. Recently it was proposed that the type of communication channel, if it offers large possibilities in the direction of evolution of the signals, could help species to differentiate in a similar way as an ecosystem with empty ecological niches would. Olfactory communication could be such a modality since compared to other modes of communication, acoustic or visual, it benefits from a large variety of signals, thanks to the tremendous diversity of chemical compounds that can be used. In addition, the specificity of the olfactory receptors necessary to detect particular chemical compounds confers a strong privacy to the information transfer, regarding illicit receivers like predators. This thesis aimed at investigating the importance of olfactory sexual communication in the evolution of reproductive isolation in the butterfly genus Bicyclus. We first compared the composition of putative male sex pheromone (pMSP) across 32 species in a phylogenetic perspective. We observed that pMSP composition was very diverse, species specific, rapidly evolving, and that stronger differences of composition likely allow species to recognise each other when sharing the same ecosystem. In a second time, we investigated the diversity of the pMSP within species and discovered similar differences as between species. This supports the hypothesis that pMSP diversification can predate speciation and can therefore be a cause of this enigmatic process. Overall, our results strongly suggest that the evolution of male sex pheromone is involved in speciation in the Bicyclus genus, and support the hypothesis that olfactory communication allows a large diversity of signals, evolving without obvious constraint, and which could rapidly lead to reproductive isolation., (SC - Sciences) -- UCL, 2015

Bacterial biofilms are the root cause of most chronic infections as- sociated with implanted materials. For the opportunistic pathogen Staphylococcus epidermidis, the development of biofilms is considered as a major virulence factor, responsible for its resilience in hospitals and in patients. There is a clear need to improve our understanding of the influences of the environment on S. epidermidis biofilm formation to propose more adapted clinical treatments to biofilms. This study aimed to gather more insights on the mechanisms of bacterial adhesion and aggregation, two essential phases of biofilm development and to develop methods to detect and control S. epidermidis in biofilms. First, the adhesion of S. epidermidis to Fibrinogen-coated surfaces was investigated. In particular, the contribution of SdrG, a cell surface adhesin, in the modulation of the adhesion of S. epidermidis to adsorbed fibrinogen was assessed. Secondly, a method to detect adhering bacteria by means of a impedimetric biosensor was developed. An original combination of optical and electrical measurements allowed to confirm the detection selectivity towards Staphylococci. Then, a novel type of aggregation was reported. Several isolates of Staphylococcus aureus and S. epidermidis were found to rapidly form large cell clumps in a reversible fashion. The implications of this phenotype on biofilm formation was also demonstrated. Finally, enzymes were used to challenge matureS. epidermidis biofilms. Lysostaphin, lysins of phage K and Twort and an analog of dispersin B were identified as potent candidates with anti-biofilm activity. Lysostaphin and lysin K could also cause significant cell lysis. These enzymes represent alternatives to the failure of antibiotics and disinfec- tants to eradicate biofilms., (AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 2015

Pollinator declines in agricultural landscapes have been attributed to the increasing scarcity of nectar sources, amongst other factors. Butterfly abundance and diversity are often correlated with nectar resource availability, but experimental, causal evidence for nectar-related effects on butterfly performance are still rare. This PhD thesis aims at evaluating the impact of a reduction in nectar quality, quantity and both combined on life-history traits and adult behaviour of a grassland butterfly in intensive, nectar-poor versus extensive, nectar-rich agricultural landscapes. We used the Meadow Brown, Maniola jurtina as a model species. We identified different foraging patterns of M. jurtina populations and individuals living in either nectar-rich grasslands and in flower-poor hay meadows, and found changes in behaviour after mowing. We tested the effects of nectar quality and quantity under semi-controlled conditions on a series of traits linked to survival, fecundity, flight performance and metabolism, and found strong negative effects of nectar limitation on butterfly condition. The differences between individuals from intensive and extensive agricultural landscapes suggested adaptations to altered resource availability relative to agricultural intensification. Consequences of agri-environmental schemes are discussed in terms of the effective use of uncut zones left in mown meadows. This PhD thesis contributes to our understanding of the importance of nectar feeding in adult butterflies, and of the significance of nectar source limitation for the population viability of flower-visiting insects in changing anthropogenic landscapes., (SC - Sciences) -- UCL, 2015

Sparing zones from mowing has been proposed, and applied, to improve local conditions for survival and reproduction of insects in hay meadows. However, little is known about the efficiency of refuge zones and the consequences for local populations. We studied population densities of butterflies before and after mowing in the refuge zone of 15 meadows in 2009 and 2011. We also studied the behaviour of the meadow brown (Maniola jurtina) comparing nectar use, interactions and flights in the refuge zone before and after mowing. Densities of grassland butterflies in this zone doubled on average after mowing. The density of females of M. jurtina increased on average fourfold, while males showed a more modest increase. In line with the idea of increased scramble competition in the refuge zone after mowing, M. jurtina increased the time spent on nectar feeding, the preferred nectar source was visited more frequently, and females made more use of non-preferred nectar sources. Maniola jurtina did not interact more with conspecifics after mowing, but interactions lasted longer. Flight tracks did not change in linearity, but were faster and shorter after mowing. After mowing, only a part of the local grassland butterflies moved to the uncut refuge zone. The resulting concentration effect alters the time allocated to different activities, nectar use and movements. These aspects have been largely ignored for agri-environmental schemes and grassland management in nature reserves and raise questions about optimal quantities and quality of uncut refuge sites for efficient conservation of grassland arthropods in agricultural landscapes.

Given the veterinary and public health impact of vector-borne diseases, there is a clear need to assess the suitability of landscapes for the emergence and spread of these diseases. Current approaches for predicting disease risks neglect key features of the landscape as components of the functional habitat of vectors or hosts, and hence of the pathogen. Empirical–statistical methods do not explicitly incorporate biological mechanisms, whereas current mechanistic models are rarely spatially explicit; both methods ignore the way animals use the landscape (i.e. movement ecology). We argue that applying a functional concept for habitat, i.e. the resource-based habitat concept (RBHC), can solve these issues. The RBHC offers a framework to identify systematically the different ecological resources that are necessary for the completion of the transmission cycle and to relate these resources to (combinations of) landscape features and other environmental factors. The potential of the RBHC as a framework for identifying suitable habitats for vector-borne pathogens is explored and illustrated with the case of bluetongue virus, a midge-transmitted virus affecting ruminants. The concept facilitates the study of functional habitats of the interacting species (vectors as well as hosts) and provides new insight into spatial and temporal variation in transmission opportunities and exposure that ultimately determine disease risks. It may help to identify knowledge gaps and control options arising from changes in the spatial configuration of key resources across the landscape. The RBHC framework may act as a bridge between existing mechanistic and statistical modelling approaches.

One of the most active disciplines in ecology these last years focuses on predicting and understanding the patterns and underlying processes of changes in species distributions under global environmental changes. Species distribution models have rapidly become the most important predictive tools in ecology to forecast the response of species to future global change. This discipline is now at a key stage of its conceptual development: it is challenged to better integrate a series of ecological processes and environmental factors that shape species distributions, abundance, community structure and ecosystem functioning. Such integration is essential to improve the ecological realism and the credibility of the future model predictions. The general objective of this PhD-thesis was to provide new perspectives in this direction. With European butterflies as model organisms, each of the core chapters tested an innovative approach focussing on the incorporation of environmental factors or ecological processes that have been neglected to date when producing future predictions. With a species distribution modelling approach addressing future shifts in species ranges, we tested the combined effect of land use and climate change, the effect of within-species spatial niche variation, and the importance of dispersal capacity for the genetic structure of the populations and persistence of the species in the future. With an experimental approach focussing on ecological processes involved during range shift, we investigated the behavioural role of habitat use to improve empirical knowledge behind the pattern of species range shifts. Based on our results, we conclude that land use change scenarios should be more often integrated with climate change scenarios in species distribution models to better reflect the response of species to global changes. We also stress the need for further development of land use change scenarios to better match the requirements of the ecological modelling, (SC - Sciences) -- UCL, 2015

Arthropods, and insects in particular, constitute important food resources for several higher trophic levels like birds. Their abundance and diversity is likely to differ between habitat types depending on the local conditions and resources. This may have important consequences for arthropod consumers that occupy structurally different habitat types. Most bird-focused studies address, however, habitats at the structural, vegetation-based level and disregard the presence of sufficient quantities and qualities of arthropod prey items. Here, we compare the quantity and quality of ground-dwelling and above-ground arthropods as food resources for early-successional birds between two structurally different human-modified habitat types sharing similar bird assemblages: low-intensity farmland areas and plantation forest clear-cut areas in the south of Belgium. Forest clear-cut patches constitute a novel habitat for so-called ‘farmland’ birds. Our results show that arthropod abundance is substantially higher in farmland than in forest clear-cuts, although arthropods are slightly larger in clear-cuts. Higher arthropod abundance is associated with higher ground-level temperature in farmland. Although both habitat types host the same spectrum of arthropod species, forest and farmland management practices induce different conditions for food quantity and, to some extent, food quality for insectivorous birds. We discuss the mechanisms behind the observed pattern of arthropod abundance and the fitness-related consequences of contrasting food availability in farmland and forest clear-cut habitats for early-successional bird species.

In human-modified environments, ecological traps may result from a preference for low-quality habitat where survival or reproductive success is lower than in high-quality habitat. It has often been shown that low reproductive success for birds in preferred habitat types was due to higher nest predator abundance. However, between-habitat differences in nest predation may only weakly correlate with differences in nest predator abundance. An ecological trap is at work in a farmland bird (Lanius collurio) that recently expanded its breeding habitat into open areas in plantation forests. This passerine bird shows a strong preference for forest habitat, but it has a higher nest success in farmland. We tested whether higher abundance of nest predators in the preferred habitat or, alternatively, a decoupling of nest predator abundance and nest predation explained this observed pattern of maladaptive habitat selection. More than 90% of brood failures were attributed to nest predation. Nest predator abundance was more than 50% higher in farmland, but nest predation was 17% higher in forest. Differences between nest predation on actual shrike nests and on artificial nests suggested that parent shrikes may facilitate nest disclosure for predators in forest more than they do in farmland. The level of caution by parent shrikes when visiting their nest during a simulated nest predator intrusion was the same in the two habitats, but nest concealment was considerably lower in forest, which contributes to explaining the higher nest predation in this habitat. We conclude that a decoupling of nest predator abundance and nest predation may create ecological traps in human-modified environments.

Brandnetels zijn alom aanwezig in een geëutrofieerd landschap op mensenmaat. Vlinders die zich specialiseren op deze waardplanten lijken het dus goed voor elkaar te hebben. Of is de ene netel toch de andere niet voor de ontwikkeling van deze insecten? We gingen dit na met veldexperimenten aan de hand van Dagpauwoog en Kleine vos. Ook de ene vlinder blijkt de andere niet.

The post-glacial recolonisation of northern Europe has left distinct signatures in the genomes of many organisms, both due to random demographic processes and divergent natural selection. However, information on differences in genetic variation in conjunction with patterns of local adaptations along latitudinal gradients is often lacking. In this study, we examine genetic diversity and population structure in the speckled wood butterfly Pararge aegeria in northern Europe to investigate the species post-glacial recolonisation history and discuss how this may have affected its life-history evolution. We collected 209 samples and analysed genetic variation in nine microsatellite loci. The results demonstrated a more pronounced population structure in northern Europe compared with populations further south, as well as an overall decrease in genetic diversity with latitude, likely due to founder effects during the recolonisation process. Coalescent simulations coupled with approximate Bayesian computation suggested that central Scandinavia was colonised from the south, rather than from the east. In contrast to further south, populations at the northern range margin are univoltine expressing only one generation per year. This suggests either that univoltinism evolved independently on each side of the Baltic Sea, or that bivoltinism evolved in the south after northern Europe was recolonised., AuthorCount:8

Dispersal, the movement of individuals among populations, is a life history trait that affects ecological and evolutionary dynamics of species. It has gained much interest in the context of metapopulation dynamics which aim to understand how species cope with habitat loss and fragmentation. In this thesis, I used controlled microcosms of a unicellular organism, the ciliate Tetrahymena thermophila, to experimentally investigate various aspects of dispersal ecology. Firstly, I describe how digital image and video analysis can be used to rapidly and reliably quantify traits and abundances of the model organism. Secondly, I investigated the relative roles of the genotype and the environment on dispersal in a two-patch system by comparing how 44 genetically different lines dispersed in response to conspecific density. We found genetic variation for dispersal plasticity and hence potential for dispersal plasticity to evolve. Thirdly, I report how an individual-based simulation model parameterized with characteristics of video-recorded cell trajectories accounted for 45% of the variation in dispersal observed among genotypes. Finally, I describe the dispersal syndromes (co-variation of dispersal with other traits) found in this set of genotypes, which bear important information about the costs and evolution of dispersal: (1) negative co-variation of dispersal-related traits with peak cell density and cell survival; (2) the absence of a link between short- and long-distance dispersal. The results in this thesis contribute to our understanding of condition-dependent dispersal, dispersal syndromes, links with the general movement ecology and introduce several methodological advances widely applicable in experimental laboratory systems., (SC - Sciences) -- UCL, 2014

Global change may strongly affect the geographic distribution of species and induce local extinctions of populations. These changes are expected to induce a loss of intraspecific genetic diversity that may, in turn, induce a decrease in the adaptation potential of the species under changing environmental conditions. Species with limited dispersal abilities, narrow habitat requirements and geographically restricted and isolated distribution patterns, such as the Violet Copper butterfly Lycaena helle, are particularly threatened. It is therefore important to evaluate the amount of intraspecific genetic diversity that can be lost in the future to guide proactive conservation strategies able to preserve the adaptation potential of L. helle. The restriction of these populations to high-elevation exclaves has led to the evolution of unique morphological and genetic entities, mostly restricted to single mountain massifs. In this study, we examine how future climate and land use changes in Europe are expected to induce range shifts and range contraction in L. helle and how these changes may cause extinction of populations and loss of intraspecific genetic uniqueness. We jointly used a species distribution modelling approach and a comprehensive microsatellite dataset to identify the populations of L. helle with unique alleles that are expected to be the most threatened with extinction under future global change. We have estimated population extinction and loss of genetic uniqueness under two dispersal assumptions: no dispersal and limited dispersal. Our results indicate that up to half of the currently known populations of L. helle are predicted to become extinct by 2080 under the most severe global change scenario. As a consequence, up to one third of the genetic uniqueness is predicted to be lost in Europe.We found considerable variation in the loss of genetic uniqueness depending on the scenarios used in the projections and on the dispersal assumptions. We suggest that pr

Landscape, including land use and land cover composition and structure, are recognized as important drivers for vector-borne disease risk. Since vector-borne pathogens rely on at least one vector and one host species, the occurrence of a disease is linked to areas where habitats of these species overlap functionally. The fact that these areas do not necessarily coincide with specific vegetation types hampers the correct identification of areas at risk. In this paper, we explore the potential of a resource-based habitat concept (RBHC) in identifying ‘suitable habitats’ for vector-borne pathogens. The resource-based habitat concept has been much used in conservation ecology, but has not been used yet in disease ecology. This concept would offer a framework to systematically study the different resources that are necessary for the completion of the transmission cycle, and link these resources to landscape features and other environmental factors. We show that the RBHC can be adapted to the multi-species setting of a vector-borne pathogen and illustrate this by applying the concept to bluetongue, a midge-transmitted virus in ruminants. We discuss the usefulness of the concept for vector-borne diseases and we argue that the concept may enable us to study the functional habitats of all the relevant species (vectors as well as hosts), which will give new insight in the spatial and temporal variation in transmission opportunities and the resulting disease risk. Also, it may facilitate communication between modellers and entomologists, help in identifying knowledge gaps and data gaps. Our framework may help act as a bridge between existing bottom-up mechanistic modelling approaches, that do not include landscape factors at all, and top-down satellite image-based approaches that are based on statistical inferences only.

The post-glacial recolonisation of northern Europe has left distinct signatures in the genomes of many organisms, both due to random demographic processes and divergent natural selection. However, information on differences in genetic variation in conjunction with patterns of local adaptations along latitudinal gradients is often lacking. In this study, we examine genetic diversity and population structure in the speckled wood butterfly Pararge aegeria in northern Europe to investigate the species post-glacial recolonisation history and discuss how this may have affected its life-history evolution. We collected 209 samples and analysed genetic variation in nine microsatellite loci. The results demonstrated a more pronounced population structure in northern Europe compared with populations further south, as well as an overall decrease in genetic diversity with latitude, likely due to founder effects during the recolonisation process. Coalescent simulations coupled with approximate Bayesian computation suggested that central Scandinavia was colonised from the south, rather than from the east. In contrast to further south, populations at the northern range margin are univoltine expressing only one generation per year. This suggests either that univoltinism evolved independently on each side of the Baltic Sea, or that bivoltinism evolved in the south after northern Europe was recolonised.

Habitats selected for development may have important fitness consequences. This is relevant within the framework of niche shifts in human-dominated landscapes. Currently, the peacock butterfly (Aglais io) occurs ubiquitously, covering many habitat types, whereas its distribution used to be much more restricted. Indeed, its host plant (stinging nettle Urtica dioica) was limited to natural forest gaps on relatively nitrogen-rich soil, but due to land use changes and eutrophication, host plants are now quasi-omnipresent in Western Europe. In order to assess the impact of specific anthropogenic habitat types on host plant quality and environmental conditions for phenotypic trait values, an experiment was conducted in woodlands, field margins, and urban gardens. Larval development was studied in field enclosures, and adult traits were analyzed to test predicted effects of warmer and more nitrogen-rich conditions in field margins compared to woodlands and urban gardens. Survival to the adult stage was highest in woodlands and lowest in field margins, and whilst development time did not differ amongst habitat types, butterflies that developed in field margins were larger and had higher lipid content and wing loadings than conspecifics from woodlands and urban gardens. Nettles in field margins provided warmer microclimates. However, and contrary to predictions, the nitrogen level within host plant leaves was highest in woodlands. Hence, anthropogenic landscapes may pose a conflict for choosing what is ultimately the best breeding habitat, as survival was highest in woodlands (followed by urban gardens), but adults with highest fitness predictions were produced in field margins (and secondarily urban gardens).

Bioluminescence, i.e. the ability for living organisms to emit light, is a widespread phenomenon in deep-ocean, due to valuable ecological advantages it provides to organisms endowed with this capability. Six percent of deep-sea cartilaginous fishes (sharks, rays, skates and chimaeras) are luminous. Among them, the lantern shark Etmopterus spinax Linnaeus, 1758 is one of the most commons and can be easily caught. For this reason, it has recently become a model species for studying bioluminescence in shark. Although various aspects (functions and control) of this complex phenomenon are now better understood in this species, the photocyte (i.e. the light-emitting cell) mechanism of light emission remains unsolved. This is the subject addressed in this work. In the first chapter, photophore ultrastructure is explored since it is a key step in investigating an unknown bioluminescent mechanism. By using transmission electron microscopy (TEM), we were able to describe photophore fine organization (Paper 1): a new structure, a reflector, which was believed to be absent in shark photophores, was highlighted. Photocytes were found to be divided into three distinct areas, of which the apical one, oriented toward the photophore center and containing numerous granular inclusions, was proved to be the light-emitting area (Paper 2). By investigating photocyte ultrastructural changes during the course of a lightemission event, we proved granular inclusion to represent shark microsource (i.e. the intracellular light-emitting site, where the chemiluminescent reaction takes place), and we proposed the term “glowon” to characterize this novel particle (Paper 2). In the second chapter, we addressed E. spinax feeding habits in order to identify putative luminous preys and analyze whether the shark could obtain a known luciferin (i.e. the luminous substrate) through its diet and use it for its own light production. The results we obtained (Paper 3) suggested E. spinax does not use a know, (SC - Sciences) -- UCL, 2014

Given the veterinary and public health impact of vector-borne diseases, there is a clear need to assess the suitability of landscapes for the emergence and spread of these diseases. Current approaches for predicting disease risks neglect key features of the landscape as components of the functional habitat of vectors or hosts, and hence of the pathogen. Empirical-statistical methods do not explicitly incorporate biological mechanisms, whereas current mechanistic models are rarely spatially explicit; both methods ignore the way animals use the landscape (i.e. movement ecology). We argue that applying a functional concept for habitat, i.e. the resource-based habitat concept (RBHC), can solve these issues. The RBHC offers a framework to identify systematically the different ecological resources that are necessary for the completion of the transmission cycle and to relate these resources to (combinations of) landscape features and other environmental factors. The potential of the RBHC as a framework for identifying suitable habitats for vector-borne pathogens is explored and illustrated with the case of bluetongue virus, a midge-transmitted virus affecting ruminants. The concept facilitates the study of functional habitats of the interacting species (vectors as well as hosts) and provides new insight into spatial and temporal variation in transmission opportunities and exposure that ultimately determine disease risks. It may help to identify knowledge gaps and control options arising from changes in the spatial configuration of key resources across the landscape. The RBHC framework may act as a bridge between existing mechanistic and statistical modelling approaches., SCOPUS: ar.j, info:eu-repo/semantics/published