MSc (Botanty) / Department of Botany / Background: Problem plants and alien invasive weed species are part of today‟s ecological transformation. Ethnobotanical literature on ecological prominence and ethical values of problem alien weeds is scant and should be documented to avoid loss of valuable species. Aim: The study was aimed at documenting problem weeds and alien invasive plant species considered to be beneficial in deep rural communities. Materials and method: Purposeful triangulation research methods were used to ensure the proper gathering of both qualitative and quantitative data sets. Results and conclusion: Some problem weeds and alien invasive plant species are being utilized by local people to maintain their livelihood. A total of 78 plant species from 33 families were recorded. These plant species belonged to diverse growth habits, namely: climbers, herbaceous, succulents, shrubs, trees as well as creepers. Recorded problem weeds and alien invasive plant species were contributing towards ecological, medicinal and social values. These included being utilized as a source of food (14), fruits (4), medicinal (31), ornamentals (7), firewood (3), social (2) and multiple purposes (17). The main utilized families were Asteraceae (14.1%) and Solanaceae (14.1%). These families were mostly utilized for the purpose of medicinal and food. Plant species that were widely used are as follows: Achyrathes aspera L., Agave sisalana L., Amaranthus spinosus L., Anredera cordifolia L., Canna indica L., Centella asiatica L., Chenopodium album L., Chenopodium ambrosioides L. and Chromolaena odorata (L.) R. M. King and H. Rob. The dominant category for problem weeds and alien invasive plant species was 1b (44%) followed by weeds (35%), category 2 (9%), invaders (5%), category 3 (4%) and 1% for both category 1, 1a as well as X3. The results revealed that the legislative listing of plant species as problem weeds and alien invasive species was based on single knowledge basis system, rather than on multi-dimensional knowledge systems. Therefore, this study recommended that for judgment to be considered in decision-making, it should be based on species-specificity as well as multi-dimensional-knowledge basis. The reconciliation of inherent grapples among scientific and indigenous knowledge systems could possibly be underpinned by equal legislative consideration for the aforementioned knowledge systems especially in the establishment and implementation of environmental regulations. This could also aid with the provision to support transformation in South Africa and worldwide.

Plant invasions represent a major ecological and socio-economical issue and understanding the drivers as well as consequences of plant invasions is thus one of the main goals of plant ecology. It is equally important to reveal general patterns underlying plant invasions and to understand the details of biology of individual invaders. In this thesis I explored plant-soil feedback (PSF) as a possible general mechanism underlying plant invasiveness, and also focused in detail on drivers and consequences of Impatiens parviflora invasion. The aims of this thesis were to i) assess the differences in intraspecific PSF between invasive and alien non-invasive species using a large set of species; ii) explore the relationship between PSF, residence time and phylogenetic novelty of the alien species; iii) compare the importance of PSF and other plant characteristics for plant invasiveness; iv) compare PSF between invasive and native congeners of similar level of dominance in the field; v) evaluate the effect of cultivating conditions on results of PSF experiments; vi) describe invasion dynamics and determine factors affecting spread of invasive I. parviflora using a method of monitoring its natural spread in several types of habitats, and vii) assess the impact of I. parviflora on native vegetation of oak-...

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<p>Here, we seek to address the importance of biodiversity in plant ecosystems. We examined the productivity-diversity relationship through the lens of the modern coexistence theory, using a combination of both experimentation and mathematical simulation. We did this by tracking and comparing the productivity of mixed and monoculture plots, analyzing the growth responses of individual trees at forest plots (Chapter 1), confirming the productivity-diversity relationship in a greenhouse experiment using local herbaceous plants (Chapter 2), and finally simulating the productivity response of monoculture vs polyculture plantations to specialist enemy attack (Chapter 3).</p><p>It is no surprise that biodiversity has been decreasing at an exponential rate on the global scale because of effects such as habitat fragmentation, invasive species, spreading pathogens, and anthropogenic influences. Ecologists often found that plants in more species rich locations often exhibited higher productivity and stability in the face of stress. One such phenomenon is known as the productivity diversity relationship that implies biodiversity is key to sustaining ecosystems. Notably, while efforts are being put forth to address ecosystem destruction, much of the current tree planting strategy in the USA is based on timber profit rather than forest productivity and species coexistence with tree biology often being a secondary consideration. These thought processes are in opposition with historical experiments that indicate polyculture communities create more biomass making them significantly more productive than monocultures. However, we also acknowledge that it is not simply biodiversity that must be taken into consideration for a productive ecosystem but also species interaction through coexistence indicate whether or not a community will persevere. These interactions can be addressed using the modern coexistence theory which depends on these complementarity and fitness similarities for species to coexist through time. Here, we seek to address the importance of biodiversity in plant ecosystems. We examined the productivity-diversity relationship through the lens of the modern coexistence theory, using a combination of both experimentation and mathematical simulation. We did this by tracking and comparing the productivity of mixed and monoculture plots, analyzing the growth responses of individual trees at forest plots (Chapter 1), confirming the productivity-diversity relationship in a greenhouse experiment using local herbaceous plants (Chapter 2), and finally simulating the productivity response of monoculture vs polyculture plantations to specialist enemy attack (Chapter 3). Our research across the combination of approaches used found that species with overlapping niches and very different finesses will exclude one another due to high competition. Further, the productivity diversity correlation is necessary for ecosystem growth, but it is not sufficient for species coexistence. However, species can maintain this positive relationship despite a lack of coexistence if they maintain niche complementarity. Lastly, using a theoretic game model we were able to identify the impacts of a specialist pest on polyculture and monoculture forest. These results showed that a polyculture forest was more productive than that of a monoculture forest regardless of the presence of a specialist enemy. The results of the multiple threads of evidence found from these combined experiments indicate that while the productivity diversity correlation is important to ecosystems it is likely due to the impacts of niche complementarity that determine whether or not species will be productive within an ecosystem.</p>

El objetivo de esta Tesis Doctoral es estudiar diferentes herramientas para el manejo de plagas y enfermedades del cultivo de la platanera. Entre las herramientas que vamos a desarrollar, se van a analizar los compuestos orgánicos volátiles (COVs) fúngicos derivados de hongos entomopatógenos (HE) y nematófagos, como fuente de metabolitos con actividad antagónica contra el picudo negro (PN) de la platanera, Cosmopolites sordidus, para su control y manejo en el campo. Así mismo, vamos a estudiar las respuestas de cultivares de plataneras a quitosano, un polisacárido biodegradable, para evaluar su posible uso en el campo como estimulante y protector de las plantas frente a plagas y patógenos, como Fusarium oxysporum f. sp. cubense. El conjunto de capítulos de esta tesis pretende sentar las bases de una estrategia de manejo sostenible de plagas y enfermedades del cultivo de la platanera, basada en el uso de COVs derivados de hongos presentes de forma natural en los cultivos, en combinación con la suplementación de quitosano en el riego, para un efecto de protección y activación de las defensas de las plataneras antes de cualquier infección de plagas y/o enfermedades. El objetivo principal de esta Tesis Doctoral es encontrar nuevas fórmulas para la gestión integrada de plagas como Cosmopolites sordidus y enfermedades de la platanera en condiciones de campo. En esta Tesis Doctoral hemos ideado enfoques sostenibles para la gestión de las plagas y enfermedades de las plataneras. Nuestros objetivos son: a) Cosmopolites sordidus (picudo negro de la platanera, PN), la principal plaga de los cultivos de plátano y, b) el hongo del marchitamiento Fusarium oxysporum f. sp. cubense Raza Tropical 4 (FocTR4), agente causante de una nueva variante extremadamente virulenta de la enfermedad del “Mal de Panamá”, que se está extendiendo rápidamente por todo el mundo. Nuestras herramientas de gestión sostenible son: a) los hongos entomopatógenos (HE, conocidos por su uso como agentes de control biológico, ACBs) aislados de campos comerciales de plátanos, b) sus compuestos orgánicos volátiles (COVs) y, c) el quitosano, un compuesto biodegradable y elicitor de la inmunidad de las plantas con actividad antimicrobiana. Damos evidencia de que los COVs de los hongos agentes de control biológico son repelentes del PN. Pueden utilizarse en los cultivos de platanera mediante estrategias de push and pull para gestionar la plaga de forma sostenible. El quitosano puede utilizarse en el riego para prevenir las defensas de la platanera local y sistémicamente. Por lo tanto, este polímero, con probada actividad antimicrobiana frente a otros patógenos de marchitamiento de Fusarium spp., podría utilizarse contra la actual pandemia en las plataneras causada por FocTR4. La capacidad de inducir reguladores del crecimiento de las plantas sostiene también el papel fertilizante del quitosano. La inducción de compuestos relacionados con la respuesta sistémica adquirida (RSA) hace que el riego con quitosano sea una herramienta para manejar también las plagas de las plataneras sobre el suelo (PN) y las enfermedades (Sigatoka). De esta manera, los COVs y el quitosano podrían ayudar a reducir el uso de agroquímicos tóxicos en los cultivos de platanera en todo el mundo.

<p dir="ltr">In this dissertation, I explore how human actions (climate change, road salt, land use change, species invasions) interact with and influence morphology, disease, and population dynamics in freshwater organisms (amphibians and aquatic crustaceans). First, I examined how the incidence and timing of disease epidemics in native species (<i>Daphnia dentifera</i>) caused by a generalist parasite (<i>Metschnikowia bicuspidata</i>) influenced the success and impact of an invasive species (<i>Daphnia lumholtzi</i>) in freshwater zooplankton (Chapter 1). In the following chapter, I explored how host-parasite interactions are affected by the interactive effects of multiple environmental stressors, focusing on American bullfrog tadpoles (<i>Lithobates catesbeianus</i>), two of their common parasites (<i>Batrachochytrium dendrobatidis</i> (<i>Bd</i>) and trematode parasites in the family Echinostomatidae), and two common stressors (fluctuating temperatures and sublethal road salt pollution; Chapter 2). Finally, I investigated how the combination of climate (temperature and precipitation) and land use (developed and/or forested area) change have influenced the body size of a common toad (Fowler’s toad, <i>Anaxyrus fowleri</i>) from 1930 – 2020 utilizing museum specimens (Chapter 3). Together, this research establishes how emerging and persistent anthropogenic environmental stressors will interact to affect morphology, disease, and population dynamics in vulnerable freshwater organisms.</p>

[ES] El cangrejo azul Callinectes sapidus es un cangrejo nadador de gran tamaño que se ha asentado en distintos lugares alrededor del mundo como especie invasora, incluida la costa mediterránea española, en la que cuenta con una fuerte presencia. Es natural de la costa atlántica de América, desde Canadá a Argentina. Es eurihalino y euritermo, voraz, y capaz de alcanzar altas densidades de población, por tanto, capaz de provocar graves impactos sobre el ecosistema autóctono. Vive habitualmente en sistemas estuarinos, que las hembras abandonan para completar su complejo ciclo vital. Se trata de una especie de interés comercial, ampliamente explotado en su zona de distribución nativa. En este estudio se han llevado a cabo un total de 7 campañas de muestreo para obtener información sobre cada una de las fases de su ciclo de vida. Para obtener información sobre la etapa inicial de vida planctónica se realizaron arrastres pelágicos. Para capturar megalopas y juveniles se emplearon colectores pasivos, y nasas para capturar adultos. Estas campañas de muestreo proporcionan información espacial y temporal sobre cada una de estas fases. En el caso de los individuos adultos permiten caracterizar su población en base al tamaño promedio de los individuos y la proporción de sexos. Además, se han realizado experimentos de modelado y simulación para determinar su posible impacto sobre las especies locales. Por una parte, se han llevado a cabo experimentos de competencia contra Pachygrapsus marmoratus, y por otra, se ha desarrollado un modelo de la red trófica de L'Albufera en "Ecopath with Ecosim". El conjunto de las campañas de muestreo revela un ciclo vital bien definido, con un periodo de apareamiento en abril-junio, una migración reproductiva en julio, un máximo de zoeas en agosto y el periodo septiembre-noviembre como el más importante a lo largo del año para la colonización de sistemas estuarinos por parte de megalopas y juveniles. Las zoeas fueron más abundantes a 1000 m de la costa, y la población de adultos capturados poseía un tamaño promedio elevado y una proporción de sexos con mayoría de hembras. Se capturaron adultos en todas las estaciones del año. P. marmoratus no se ve especialmente afectado por la presencia de C. sapidus. Según el modelo, la especie más afectada por C. sapidus en L'Albufera es Procambarus clarkii, existiendo impactos variados sobre otras especies. La pesca se revela como un mecanismo eficaz de control de la población de C. sapidus. / [CA] El cranc blau Callinectes sapidus és un cranc nadador de gran grandària que s'ha assentat en diferents llocs al voltant del món com a espècie invasora, inclosa la costa mediterrània espanyola, en la qual compta amb una forta presència. És natural de la costa atlàntica d'Amèrica, des del Canadà a l'Argentina És eurihalino i euritermo, voraç, i capaç d'aconseguir altes densitats de població, per tant, capaç de provocar greus impactes sobre l'ecosistema autòcton. Viu habitualment en sistemes estuarinos, que les femelles abandonen per a completar el seu complex cicle vital. Es tracta d'una espècie d'interés comercial, àmpliament explotat en la seua zona de distribució nativa. En este estudi s'han dut a terme un total de 7 campanyes de mostreig per a obtindre informació sobre cadascuna de les fases del seu cicle de vida. Per a obtindre informació sobre etapa inicial de vida planctònica es van realitzar arrossegaments pelàgics. Per a capturar megalopas i juvenils es van emprar col·lectors, i nasas per a capturar adults. Estes campanyes de mostreig proporcionen informació espacial i temporal sobre cadascuna d'estes fases. En el cas dels individus adults permeten caracteritzar la seua població sobre la base de la grandària mitjana dels individus i la proporció de sexes. A més, s'han realitzat experiments de modelatge i simulació per a determinar el seu possible impacte sobre les espècies locals. D'una banda, s'han dut a terme experiments de competència contra Pachygrapsus marmoratus, i per una altra, s'ha desenvolupat un model de la xarxa tròfica de L'Albufera en "Ecopath with Ecosim". El conjunt de les campanyes de mostreig revela un cicle vital ben definit, amb un període d'aparellament a l'abril-juny, una migració reproductiva al juliol, un màxim de zoeas a l'agost i el període setembre-novembre com el més important al llarg de l'any per a la colonització de sistemes estuarinos per part de megalopas i juvenils. Les zoeas van ser més abundants a 1000 m de la costa, i la població d'adults capturats posseïa una grandària faig una mitjana d'elevat i una proporció de sexes desviada cap a les femelles. Es van capturar individus adults en totes les estacions de l'any. P. marmoratus no es veu especialment afectat per la presència de C. sapidus. Segons el model, l'espècie més afectada per C. sapidus en L'Albufera és Procambarus clarkii, existint impactes variats sobre altres espècies. La pesca es revela com un mecanisme eficaç de control de la població de C. sapidus. / [EN] The blue crab Callinectes sapidus is a large swimming crab that has settled in different places around the world as an invasive species, including the Spanish Mediterranean coast, where it has a strong presence. It is native to the Atlantic coast of America, from Canada to Argentina. It is euryhaline and eurythermic, voracious, and capable of reaching high population densities, therefore, capable of causing serious impacts on the native ecosystem. It usually lives in estuarine systems, which the females leave to complete their complex life cycle. It is a species of commercial interest, widely exploited in its native range. In this study, a total of 7 sampling campaigns were carried out to obtain information on each of the stages of their life cycle. To obtain information on the initial stage of planktonic life, pelagic trawls were used. Collectors were used to capture megalopae and juveniles, and traps were used to capture adults. These sampling campaigns provide spatial and temporal information on each of these stages. In the case of adult individuals, they allow us to characterize the population based on the average size of the individuals and the sex ratio. In addition, modeling and simulation experiments have been carried out to determine their possible impact on local species. On the one hand, competition experiments have been carried out against Pachygrapsus marmoratus, and on the other hand, a model of the food web of L'Albufera has been developed in "Ecopath with Ecosim". The set of sampling campaigns reveals a well-defined life cycle, with a mating period in April-June, a reproductive migration in July, a maximum of zoeas in August and September-November as the most important period throughout the year for the colonization of estuarine systems by megalopae and juveniles. Zoeas were most abundant at 1000 m offshore, and the population of adults captured had a high average size and a sex ratio skewed towards females. Adult individuals were captured in all seasons. P. marmoratus is not particularly affected by the presence of C. sapidus. According to the model, the species most affected by C. sapidus in L'Albufera is Procambarus clarkii, with varied impacts on other species. Fishing is shown to be an effective mechanism for controlling the population of C. sapidus. / Gil Fernández, A. (2024). Adaptación e impacto ecosistémico de Callinectes sapidus Rathbun, 1896 en la costa mediterránea española: caso de L'Albufera de Valencia [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/211375

The Cape Horn Biosphere Reserve is located at the southern tip of South America. This large archipelago is considered one of the last pristine areas left on the world. Despite it being an unpopulated area with most of the native forest cover intact, it has not been exempt from biological invasions, one of the major drivers of biodiversity loss. Three species that naturally interact in their native range in North America – American beavers (Castor canadensis), muskrats (Ondatra zibethicus), and American mink (Neovison vison) – were independently introduced in this remote region. In my dissertation, I investigated (i) the hypothesis of niche expansion in the invasive mink population on Navarino Island towards terrestrial habitats; (ii) potential mink impact on breeding success of forest-bird populations; (iii) habitat selection of small-rodent species and their perception on the mink's novel predation risk; and (iv) the dynamics of multiple-species invasions under the hypothesis of an invasional meltdown. Additionally, I worked within the framework of environmental philosophy. I provide an example of combining ecological and cultural dimensions within the International Long-Term Ecological Research network to disentangle the ethical dilemmas that surround the management of invasive species. I finally proposed a management plan based on the idea of multiple invasive species management, discussing potential solutions to overcome the challenges that the control of invasive species represent and to more effectively protect the biological integrity of the native ecosystems.

To refine our knowledge and to adequately test hypotheses concerning theoretical and applied aspects of invasion biology, successful and unsuccessful invaders should be compared. This study investigated insect establishment patterns by comparing the climatic preferences and biological attributes of two groups of polyphagous insect species that are constantly intercepted at New Zealand's border. One group of species is established in New Zealand (n = 15), the other group comprised species that are not established (n = 21). In the present study the two groups were considered to represent successful and unsuccessful invaders. To provide background for interpretation of results of the comparative analysis, global areas that are climatically analogous to sites in New Zealand were identified by an eco-climatic assessment model, CLIMEX, to determine possible sources of insect pest invasion. It was found that south east Australia is one of the regions that are climatically very similar to New Zealand. Furthermore, New Zealand shares 90% of its insect pest species with that region. South east Australia has close trade and tourism links with New Zealand and because of its proximity a new incursion in that analogous climate should alert biosecurity authorities in New Zealand. Other regions in western Europe and the east coast of the United States are also climatically similar and share a high proportion of pest species with New Zealand. Principal component analysis was used to investigate patterns in insect global distributions of the two groups of species in relation to climate. Climate variables were reduced to temperature and moisture based principal components defining four climate regions, that were identified in the present study as, warm/dry, warm/wet, cool/dry and cool/moist. Most of the insect species established in New Zealand had a wide distribution in all four climate regions defined by the principal components and their global distributions overlapped into the cool/moist, temperate climate where all the New Zealand sites belong. The insect species that have not established in New Zealand had narrow distributions within the warm/wet, tropical climates. Discriminant analysis was then used to identify which climate variables best discriminate between species presence/absence at a site in relation to climate. The discriminant analysis classified the presence and absence of most insect species significantly better than chance. Late spring and early summer temperatures correctly classified a high proportion of sites where many insect species were present. Soil moisture and winter rainfall were less effective discriminating the presence of the insect species studied here. Biological attributes were compared between the two groups of species. It was found that the species established in New Zealand had a significantly wider host plant range than species that have not established. The lower developmental threshold temperature was on average, 4°C lower for established species compared with non-established species. These data suggest that species that establish well in New Zealand have a wide host range and can tolerate lower temperatures compared with those that have not established. No firm conclusions could be drawn about the importance of propagule pressure, body size, fecundity or phylogeny for successful establishment because data availability constrained sample sizes and the data were highly variable. The predictive capacity of a new tool that has potential for eco-climatic assessment, the artificial neural network (ANN), was compared with other well used models. Using climate variables as predictors, artificial neural network predictions were compared with binary logistic regression and CLIMEX. Using bootstrapping, artificial neural networks predicted insect presence and absence significantly better than the binary logistic regression model. When model prediction success was assessed by the kappa statistic there were also significant differences in prediction performance between the two groups of study insects. For established species, the models were able to provide predictions that were in moderate agreement with the observed data. For non-established species, model predictions were on average only slightly better than chance. The predictions of CLIMEX and artificial neural networks when given novel data, were difficult to compare because both models have different theoretical bases and different climate databases. However, it is clear that both models have potential to give insights into invasive species distributions. Finally the results of the studies in this thesis were drawn together to provide a framework for a prototype pest risk assessment decision support system. Future research is needed to refine the analyses and models that are the components of this system.