The role of behavioural and feedback mechanisms in mediating herbivory processes in Mediterranean seagrass ecosystems

[eng] The role of consumer-resource relationship is the basis of the structure and functioning of ecological communities. The traditional lens for studying such interactions have tended to omit the importance of the species behaviour, particularly in the case of plant-herbivore interactions. However, they way the herbivore exploits the plant and the way the plant responds to that pressure is crucial in determining the stability of the interaction. Thus, both herbivore and plant performances, contextualised in the environment where the interaction takes place, can act as drivers of the resilience of the system. This thesis focuses on Posidonia oceanica ecosystems and specifically on the interaction between this seagrass and its two main herbivores – the fish Sarpa salpa and the sea urchin Paracentrotus lividus –. I assess the importance of herbivore behaviour (the aggregation patterns and feeding behaviour of S. salpa and the canopy cover dependence of P. lividus) and the resilience provided feedback mechanisms (direct responses of the plant and indirect ecosystem processes) under changing conditions resulting from global change. Disentangling these components of the interaction allows us to assess its sensitivity to each of the components and to test the response and resilience of the system under different conditions. Chapter 1 shows the importance of body size of Sarpa salpa individuals in their individual feeding activity, shoaling aggregation patterns and shoal feeding strategies, as well as the potential consequences of this on the seagrass P. oceanica. On the one hand, the larger the individuals are, the more feeding activity they show. On the other hand, S. salpa individuals tend to aggregate with conspecifics of the same body size and group size is positively related to the size of the individuals in the group. In addition, feeding strategies increase in complexity with group size and tend to be focused on very specific spots within the meadow. Thus, as individuals grow, they increase their potential impact on the seagrass, both in terms of their consumption capacity and the formation of large shoals capable of concentrating their consumption in very specific areas of the meadow. This distribution of herbivory can lead to spatial heterogeneity with consequences for the functioning of the ecosystem dominated by P. oceanica. In chapter 2, a number of regulatory mechanisms arising from an episode of intense herbivory are found to provide resilience to Posidonia oceanica system once its canopy height is reduced. Four of the mechanisms evaluated function as feedback mechanisms, one of them being actively deployed by the plant (compensatory growth) while the other three (preference for an alternative resource, increased risk of predation and reduced urchin numbers due to competition for the resource and loss of cover) are triggered indirectly and their effectiveness is based on inducing changes in the behaviour of the herbivore Paracentrotus lividus. The results obtained show how P. oceanica is able to invest efforts in recovering part of the lost leaf biomass while the system itself is able to regulate herbivory pressure as long as the environmental conditions are appropriate to the occurrence of these mechanisms. The role of these mechanisms is key to avoid the potential collapse of P. oceanica meadows under the stress caused by an episode of intense herbivory. In chapter 3, the effect of global warming on the Posidonia oceanica – Sarpa salpa interaction is assessed through a combination of gradient approaches in the field and manipulative laboratory experiments. On the one hand, the results show that increasing water temperature significantly increases S. salpa growth rates during its larval stage, reducing its larval period (fewer days in the water column) and limiting its dispersal, while showing no effect on feeding behaviour during its adult phase. On the other hand, warming negatively affects the growth rates of P. oceanica and makes it more palatable towards S. salpa according to the results from the preference experiment. Our study shows that S. salpa could develop faster in warmer environments during its most vulnerable stage, increasing its survival but decreasing its dispersal capacity. At the same time, it could increase its preference for P. oceanica in its adult stage, which, together with the reduction of seagrass growth, could considerably intensify the strength of the interaction under warming conditions. All in all, the results of this study have contributed to confirm the relevance of herbivores’ behaviour in the way they exploit P.oceanica, mainly the feeding strategies of S. salpa, and how feedback mechanisms, provide resilience and allow the ecosystem to be maintained in an vegetated state. All of this gets relevant when contextualised within the process of global change, with a probable strengthening of the plant-herbivore interaction. Understanding the sensitivity of the interaction equilibria to each of its components is crucial to decide where to invest conservation efforts in these ecosystems and to be able to anticipate how changes in the contextual conditions may alter the final balance of the interaction.[spa] El papel de la relación consumidor-recurso es la base de la estructura y el funcionamiento de las comunidades ecológicas. La óptica tradicional usada en el estudio de estas interacciones ha tendido a omitir la importancia del comportamiento de las especies, sobre todo en el caso de las interacciones planta-herbívoro. Sin embargo, tanto la forma en la que el herbívoro explota a la planta y como la manera en que ésta responde a esa presión son cruciales para determinar la estabilidad de la interacción. Por lo tanto, las actuaciones del herbívoro y la de la planta, contextualizadas en el entorno en el que tiene lugar la interacción, pueden actuar como mediadores de la resiliencia del sistema. Esta tesis se centra en los ecosistemas de Posidonia oceanica y, concretamente, en la interacción entre esta fanerógama con sus dos principales herbívoros -el pez Sarpa salpa y el erizo de mar Paracentrotus lividus-. En esta tesis se evlaúa la importancia del comportamiento de los herbívoros (los patrones de agregación y las estrategias de alimentación de S. salpa y la dependencia de la cobertura foliar de P. lividus) y la resiliencia proporcionada por los mecanismos de retroalimentación (respuestas directas de la planta y procesos indirectos del ecosistema) bajo condiciones cambiantes resultantes del cambio global. Desentrañar estos componentes de la interacción nos permite evaluar su sensibilidad a cada uno de los dichos componentes y comprobar la respuesta y la resiliencia del sistema bajo diferentes condiciones. En el capítulo 1 se muestra la importancia del tamaño del cuerpo de los individuos de Sarpa salpa en sus tasas de consumo individual, en sus patrones de agregación y en las estrategias alimenticias de grupos, además de las potenciales consecuencias de estos procesos sobre la fanerógama Posidonia oceanica. Por un lado, cuanto mayores son los individuos, mayores tasas de consumo muestran. Por otro, los individuos de S.salpa tienden a agregarse con conspecíficos de la misma talla, mientras que el tamaño de los grupos se relaciona positivamente con la talla de los individuos que lo forman. Además, las estrategias de alimentación aumentan en complejidad con el tamaño del grupo y tienden a focalizarse en puntos muy concretos de la pradera. Así, a medida que los individuos crecen, aumentan su potencial impacto en la fanerógama, tanto por su capacidad de consumo como la formación de grandes bancos capaces de concentrar su herbivoría en áreas muy concretas de las praderas. Esta distribución de la herbivoría puede provocar una heterogeneidad espacial con consecuencias sobre el funcionamiento del ecosistema dominado por P. oceanica En el capítulo 2 se comprueba la existencia de una serie de mecanismos reguladores surgidos de un episodio de herbivoría intensa que aportan resiliencia al sistema de Posidonia oceanica una vez disminuida su bóveda foliar. Cuatro de los mecanismos evaluados funcionan como mecanismos de retroalimentación, siendo uno de ellos desplegado activamente por la planta (crecimiento compensatorio) mientras que los tres restantes (preferencia por un recurso alternativo, incremento del riesgo de depredación y disminución del número de erizos por competencia por el recurso y pérdida de cobertura) se desencadenan de forma indirecta y su eficacia se basa en inducir cambios en el comportamiento del herbívoro Paracentrotus lividus. Los resultados obtenidos muestran como P. oceanica es capaz de invertir esfuerzos en recuperar parte de la biomasa foliar perdida, mientras que el mismo sistema es capaz de regular la presión de herbivoría siempre que las condiciones del entorno sean propicias para la aparición de dichos mecanismos. El papel resiliente de estos mecanismos es clave para evitar el potencial colapso de las praderas de P. oceanica bajo el estrés provocado por un episodio de herbivoría intensa. En el capítulo 3 se evalúa el efecto del calentamiento global en la interacción Posidonia oceanica – Sarpa salpa a través de una combinación de aproximaciones de gradiente en campo con experimentos manipulativos de laboratorio. Por un lado, los resultados muestran que el aumento de la temperatura del agua incrementa significativamente las tasas de crecimiento de S.salpa durante su etapa larval, acorta su período en dicha etapa (menos días en la columna de agua) y limita su dispersión, mientras que no muestra ningún efecto en la actividad herbívora durante su fase adulta. Por otro lado, el calentamiento afecta negativamente las tasas de crecimiento de P. oceanica y la vuelve más palatable frente a S. salpa de acuerdo con los resultados en el experimento de preferencia. Nuestro estudio muestra que S. salpa podría desarrollarse más rápido en su etapa más vulnerable, aumentando su supervivencia, pero disminuyendo su capacidad de dispersión, mientras que podría incrementar su preferencia por P. oceanica en su etapa adulta, lo que, junto con la reducción del crecimiento de la fanerógama, podría intensificar considerablemente la fuerza de la interacción. En definitiva, los resultados de esta tesis han servido para constatar la relevancia del comportamiento de los herbívoros en su forma de explotar el recurso, principalmente las estrategias de alimentación de S. salpa, y como los mecanismos de retroalimentación aportan resiliencia y permiten al ecosistema mantenerse en un estado óptimo. Todo ello cobra más importancia al contextualizarlo dentro del proceso del cambio global, dado el probable fortalecimiento de la interacción planta-herbívoro. Conocer la sensibilidad de la interacción a cada uno de los componentes es crucial para decidir donde hay que invertir los esfuerzos de conservación en estos ecosistemas y poder así anticiparnos a como los cambios en las condiciones de contorno pueden alterar el equilibrio final de la interacción

Behavioral response of mule deer to natural gas development in the Piceance Basin

2015 Spring.Includes bibliographical references.To view the abstract, please see the full text of the document

The role of piscivores in a species-rich tropical river

Much of the world's species diversity is located in tropical and sub-tropical ecosystems, and a better understanding of the ecology of these systems is necessary to stem biodiversity loss and assess community- and ecosystem-level responses to anthropogenic impacts. In this dissertation, I endeavored to broaden our understanding of complex ecosystems through research conducted on the Cinaruco River, a floodplain river in Venezuela, with specific emphasis on how a human-induced perturbation, commercial netting activity, may affect food web structure and function. I employed two approaches in this work: (1) comparative analyses based on descriptive food web characteristics, and (2) experimental manipulations within important food web modules. Methodologies included monthly sampling of fish assemblages using a variety of techniques, large-scale field experiments, extensive stomach content and stable isotope analyses. Two themes unite the information presented: (1) substantial spatial and temporal variability in food web structure, and (2) how body-size can be used to generalize species-interactions across this complexity. Spatial variability occurred at various scales, from among small fish assemblages on seemingly homogeneous sand banks, to differences among landscape scale units (e.g. between lagoons and main river channel). Seasonal variability was apparent in predation patterns, with relative prey availability and body size primarily resulting in decreasing prey sizes with falling water levels. Body size was also related to functional outcomes of species interactions, for example, a size-based response of prey fishes to large-bodied piscivore exclusion. This pattern was further substantiated at the landscape-scale, as differences in assemblage structure among netted and un-netted lagoons were largely size-based. Trophic position of fish and body size was not found to be related, likely due to the diversity of prey available to consumers, and may signify that commercial netting activity will not decrease food chain lengths. In sum, by describing human impacts within a food web context, I endeavor to provide predictive power regarding a specific human-induced environmental problem, yet still allowing for generality that will broaden the theoretical foundations and applications of food web ecology

Simultaneous Multispectral Imaging: Using Multiview Computational Compressive Sensing

Multispectral imaging is traditionally performed using a combination of an imaging device with a filter bank such as a filter wheel or a form of tunable filter, or a combination of many imaging devices with various spectral beam splitting optics. The complexity and size of these devices seem to be the limiting factor of their adoption and use in various fields that could potentially benefit from this imaging modality. With the advent of nanophotonics, there has been a surge in single camera, snapshot, multispectral imaging exploiting the capabilities of nanotechnology to devise pixel-based spectral filters. This new form of sensing, which can be classified as compressive sensing, has its limitations. One example is the laborious process of fabricating the filter bank and installing it into a detector since the detector fabrication process is completely removed from the filter fabrication process. The work presented here will describe an optical design that would enable a single-camera, simultaneous multispectral imaging via multiview computational compressive sensing. A number of points-of-view (POVs) of the field-of-view (FOV) of the camera are generated and directed through an assortment of spectral pre-filters en route to the camera. The image of each of the POVs is then captured on a different spatial location on the detector. With the spectral response of the detector pixels well characterized, spatial and spectral compressive sensing is performed as the images are recorded. Various computational techniques are used in this work which would: register the images captured from multiple views resulting in even more sparsely sensed images; perform spatial interpolation of the sparsely sampled spectral images; implement hyper-focusing of the images from all POVs captured as some defocusing will happen as the result of the discrepancy in the optical paths in each view; execute numerical dimensionality reduction analysis to extract information from the multispectral images. The spectral imaging capabilities of the device are tested with a collection of fluorescent microspheres. The spectral sensing capability of the device is examined by measuring the fluorescent spectra of adulterated edible oils and demonstrating the ability of the imaging system to differentiate between various types of oil as well as various levels of contamination. Lastly, the system is used to scrutinize samples of black ink from different pen manufacturers, and is able to discriminate between the different inks

Cascading Community Consequences of Fish Adaptation

Trophic interactions are an enduring framework for ecological thought. Broad and growing evidence for contemporary evolution has demonstrated that ecology and evolution dynamically interact on similar time scales. In this dissertation, I seek to understand how genetic and plastic trait change in human-influenced systems shape trophic dynamics, how such trait changes are constrained by inherent tradeoffs, and the broad implications of such trait change for ecological communities. I advance the premise that competition-defense tradeoffs are the essential mechanism behind many eco-evolutionary trophic dynamics that can reshape multi-trophic communities. In support of this view, I assess the presence of ecologically relevant genetic evolution along a competition-defense tradeoff in a model species. I also employ models and experiments to quantify how the particularly strong genetic and plastic trait changes in population phenotypes generated by humans can rearrange ecological communities by altering trophic interaction strengths

Parámetros clínicos de chimpancé ("Pan troglodytes") en programas de rehabilitación y reintroducción en su medio natural

Genéticamente, los chimpancés y los bonobos son los parientes vivos más cercanos a los seres humanos, que comparten un ancestro común que vivió hace unos seis millones de años. Los chimpancés se consideran en peligro de extinción por la IUCN y numerosos programas de conservación en África trabajan hacia la protección de la especie y su hábitat. Amenazado por la caza furtiva y la destrucción del hábitat, las cifras de población de chimpancés salvajes siguen disminuyendo. Como consecuencia, un importante flujo de chimpancés en vivo que son víctimas de la caza furtiva son enviados a centros de rehabilitación en África donde viven en semilibertad y en ocasiones son reintroducidos en el medio natural. Un objetivo primordial en estos centros de rescate y rehabilitación es proporcionar a los primates en cautividad con altos estándares de bienestar. La realización de tratamientos médicos adecuados y una gestión cuidadosa contribuye a su buen estado de salud, que a su vez permite a estos centros para garantizar el bienestar óptimo chimpancé. A un nivel veterinaria, la implementación de un tratamiento rápido y efectivo para una enfermedad requiere las herramientas de diagnóstico adecuadas, así como los valores de referencia correctos correspondientes a la especie. El objetivo de la presente tesis es establecer rangos de referencia de los diferentes parámetros clínicos para el chimpancé común (Pan troglodytes), que viven en semi-libertad en su hábitat natural. A fin de establecer valores de referencia, hemos utilizado los datos obtenidos durante los controles de rutina del brezo en chimpancés realizados durante diez años, en Tchimpounga Centro de Rehabilitación de chimpancé. Todos los chimpancés en el Centro de Rehabilitación Tchimpounga someten a controles de salud a su llegada al centro y en adelante cada tres años. Los análisis se llevan a cabo para asegurar la buena salud de la comunidad, y mejorar el control de la transmisión de enfermedades infecciosas, como la tuberculosis. Los análisis incluyen la recogida de sangre de la muestra, electrocardiogramas, radiografías de tórax, ecografía abdominal y pruebas serológicas y bacteriológicas. Estos análisis requieren la inmovilización química del individuo. A su vez, otros controles de salud que no requieren inmovilización química se realizan a diario en el centro por personal cualificado. Estos incluyen el análisis de las heces y la orina, y la exploración física general. La exploración global incluye tomar la temperatura corporal diaria de los chimpancés menores de 10 años en virtud de condicionamiento positivo..

Intelligent Sensor Networks

In the last decade, wireless or wired sensor networks have attracted much attention. However, most designs target general sensor network issues including protocol stack (routing, MAC, etc.) and security issues. This book focuses on the close integration of sensing, networking, and smart signal processing via machine learning. Based on their world-class research, the authors present the fundamentals of intelligent sensor networks. They cover sensing and sampling, distributed signal processing, and intelligent signal learning. In addition, they present cutting-edge research results from leading experts

The effects of simulated catch-and-release angling on adult Atlantic salmon (Salmo salar) and their offspring

Fish, including Atlantic salmon (Salmo salar), are released by anglers after capture as part of a fisheries management tool known as catch and release (C&R) angling. This has been introduced as a conservation measure to try and halt, or even reverse, the continuous decline in Atlantic salmon numbers. Consequently, prespawned salmon may now experience C&R during the freshwater migration to the spawning grounds. Yet, there is still limited information in this area, including how stress from capture prior to breeding can affect not only the fecundity of the parents, but also the phenotype of the offspring. This study explores how two of the main stressors associated with C&R angling, exercise and air exposure, experienced by the parents shortly (5 – 18 days) prior to spawning affect adult mortality, physiology and reproduction. It also investigates the effects of simulated C&R on the early developmental stages of the progeny, as well as examines its influences on key behavioural (risk-taking behaviour, activity, exploration, aggression, and dominance) and physiological (SMR, MMR, AS) traits in offspring. An equal number of male and female wild adult Atlantic salmon were captured using a permanent fish trap, set up by the Cromarty Firth Fisheries, on the river Blackwater, N. Scotland, during their spawning migration. They then experienced one of three disturbance protocols that comprised of exercise (120 s) and air exposure (0, 60, or 120 s) of different duration, similarly to what they would encounter during a C&R angling event. There was also a fourth group present that did not experience any additional disturbance and was therefore used as baseline (control group). Each experimental fish (of either sex) was later mated (using IVF) with a non-experimental counterpart, and the offspring were reared under fixed conditions. Experimental parent mortality was unaffected by the simulated C&R, however the growth rate of the fungus Saprolegnia spp. on the body of the fish increased. Furthermore, males from the treatment group exercise + extended air produced sperm that survived for longer once activated (i.e. had an increased maximum duration of sperm motility). Females that experienced disturbance spawned at the usual time, but with smaller clutches. An increase in egg and fry mortality was noted for the groups whose parents were exposed to air, mostly due to higher mortality during egg shocking (a normal husbandry practice in hatcheries to separate non-viable eggs) and an increase in fry mortality during a 12-day fungal (Saprolegnia spp.) outbreak. Moreover, adults from the most extreme treatment group (exercise + extended air exposure) produced offspring that were smaller at first feeding. As for offspring behaviour, both the activity and exploration of a novel environment were lower in the treatments whose experimental parent was exercised and then air exposed for an extended period. Similar results in exploration were observed by the offspring in the exercise group. Yet, exploration in the most extreme disturbance group was improved as the fish became bigger. Progeny from the same treatments, ‘exercise’ and ‘exercise + extended air’ also displayed higher levels of aggression. Interestingly however, during the dominance trials, both these treatment groups were subordinate to offspring from the control treatment. Fish from the control treatment exhibited dominance over the fish from the disturbed parents during the trials on the first two days, but an absence of clear dominance was observed on the third day. There was no observable difference in dominance status between the treatment ‘exercise’ and ‘exercise + extended air’ treatments. The metabolism of the offspring was only affected in the exercise group, where both the MMR and AS were reduced. These results suggest that stressing the parents shortly before spawning will not affect the timing of the spawning, but it could influence the reproductive success of the parents. Furthermore, it indicates that disturbing the parents, especially air exposing them for more than 60 s, could adversely affect the early developmental stages of the offspring, including those behavioural traits which could influence dispersal and competition from feeding territories, and thus reduce their chances of survival. The results therefore have implications for both the period over which C&R is allowed and the way in which it is implemented by anglers