Mosquitoes are the deadliest animal on the planet killing about a million people a year. These insects are competent vectors of multiple pathogens (e.g., Plasmodium sp, filarial worms, and arboviruses). In most species, females are blood feeders, and must consume a blood meal to complete a gonotrophic cycle. Extensive research has been conducted on hematophagy and host-seeking behaviors, but relatively little is known about phytophagy. Sugar feeding is an essential aspect of mosquito biology. Both male and female mosquitoes must consume sugar as a primary fuel source. Mosquitoes use olfactory and visual cues among other cues to find suitable food sources. Abiotic factors, such as temperature and humidity, have been shown to impact mosquito behaviors, including sugar feeding. Recently, sugar feeding has been identified as a promising control target for multiple species of mosquitoes. Attractive toxic sugar baits (ATSBs) attract both male and females through the use of plant derived volatiles. In this work, we first examined the effects of temperature and humidity on the survival of sugar fed Aedes aegypti. We showed that sugar feeding greatly increases longevity in optimal conditions and that humidity impacted survival while temperature less so. Second, we aimed at developing an ATSB for controlling Aedes j. japonicus mosquitoes. Overall, this work sheds light on the importance of abiotic factors and sugar feeding on mosquito survival and lays the groundwork for controlling an invasive mosquito species. / Master of Science in Life Sciences / Mosquitoes are the deadliest organisms on the planet killing about a million people each year due to the multitude of pathogens they may transmit (e.g., malaria parasites, Zika virus, dengue virus). Female mosquitoes transmit pathogens by taking blood meals to obtain essential nutrients needed to develop eggs. If knowledge on host-seeking behavior and blood-feeding is extensive, comparatively less is known about sugar feeding. Sugar feeding is an important behavior displayed by both male and female mosquitoes to obtain energy for flying, reproduction, and survival. Mosquitoes feed on a variety of sugar sources including plant nectar and decaying fruits. They use multiple different cues in order to locate suitable meals including olfaction and vision. Environmental factors such as temperature and humidity affect mosquito activity, dehydration, and sugar feeding. In the present work, we first examined the effects of temperature and humidity on survival in the major disease vector species, Aedes aegypti. As the global temperatures are increasing, it is essential to better understand how mosquitoes adapt and deal with environmental stressors in a changing world. We then aimed at exploiting sugar feeding behavior by developing a novel method of control for another invasive mosquito species, Aedes j. japonicus. Together, these results help us have a better understanding of mosquito biology and ecology which is crucial for predicting future distribution of invasive species and designing new control strategies.

<p dir="ltr">Non-native biological invasions are one of the leading concerns for global biodiversity. The establishment of invasive species reduces local biodiversity, shifts species composition, changes successional trajectories, and alters ecosystem functions. This thesis examines two aspects of invasive plants: (1) the distribution and the most important climatic and anthropogenic drivers of invasive trees across the eastern United States, and (2) an evaluation of invasive plant removal and herbaceous recovery from a government cost-share program that provides financial support for invasive plant management by private landowners.</p><p><br></p><p dir="ltr">Our first study focused on identifying the distribution of invasive trees, and the factors associated with their distribution. This is essential to predicting spread and planning subsequent management. Using USDA Forest Inventory Analysis (FIA) data and random forest modeling, we examined the distribution, and variables associated with the distribution, of invasive tree species. Invasive trees were found in 10,511 out of 299,387 FIA plots. Invasive species basal area and density (trees per ha; TPH) were highest within the central and southern Appalachian Mountains, Michigan, the Northeast, and the southern Coastal Plain of the United States. A random forest model of invasive species basal area (R²= 0.47, RMSE = 0.47) and density (R²=0.46, RMSE=0.50) vs. environmental variables found that both invasive basal area and density were most strongly associated with human footprint, followed by various climatic variables. An equivalent model of native tree basal (R²=0.53, RMSE=9.25) and TPH (R²=0.47, RMSE=8.64) found that native tree basal area and density were most strongly associated with aridity followed by various climatic variables. As human footprint increased, invasive tree basal area and density increased. These results suggest that the distribution of invasive trees is reliant on human alterations to forests.</p><p><br></p><p dir="ltr">Our second study focused on Environmental Quality Incentives Program (EQIP), a federal cost-share program that has provided $25 billion of financial assistance to farmers and non-industrial private forest owners. Few studies have examined whether this program facilitates the recovery of the herbaceous layer while decreasing the dominance of invasive plant species. We surveyed the herbaceous layer of EQIP-treated and untreated (reference) forests across three physiographic regions of Indiana. Using non-metric multidimensional scaling (NMDS) ordination and linear mixed effects models, we evaluated the species composition, richness, diversity, evenness, floristic quality index, and herbaceous-layer cover of EQIP and reference sites. We also used linear mixed models to evaluate how EQIP site treatment affected the diversity of native plant species. Sites treated with EQIP contracts typically had significantly higher native species richness, Shannon’s diversity, and floristic quality than reference sites. There were significant separations in species composition between EQIP treated and reference forests state-wide and in the southern non-glaciated region of Indiana, although composition overlapped between EQIP and reference forests. Our study suggests that EQIP-funded treatments promote increased species richness and diversity. However, the persistent overlap in species composition we observed may signify biotic homogenization due to a long-shared history of anthropogenic disturbances between EQIP and reference sites. Therefore, active restoration of the herbaceous layer might be needed to allow a full recovery after invasive removal.</p>

Biological invasion has become a major threat to economy, ecology, global biodiversity and ecosystem function of aquatic ecosystems. The main aim of the thesis was to study the effects of the zebra mussel (Dreissena polymorpha), a versatile invasive species, on phytoplankton dynamics and ecosystem function of lakes. In a first attempt, I compared the density of Dreissena and the physicochemical data of ecosystems that it invaded among North American and European lakes to identify important factors in its invasion success. Secondly, I investigated the impact of zebra mussels on phytoplankton community composition in a natural lake. Thirdly, I evaluated whether zebra mussel feeding behavior were affected by the presence of predatory waterborne cues. Finally, I examined the effect of Dreissena on seston stoichiometry. A Generalized Additive Model revealed that a joint effect of surface area, mean depth, total phosphorus and calcium concentrations can explain the variability in Dreissena density. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics. Risk cues released by predators affected both feeding rate and prey selection of the mussels and had cascading indirect effects on phytoplankton biomass and community structure. I found that the flux in nutrients caused by differences in zebra mussel consumption lead to a variation in phytoplankton nutrient limitation. The flexibility of zebra mussel feeding behavior and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences. The results of this thesis contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. The results suggested that zebra mussel can indirectly both reduce and increase the energy transfer efficiency from primary producers to upper trophic levels in the pelagic and benthic food webs, respectively.

Thesis (PhD)-- Stellenbosch University, 2012. / ENGLISH ABSTRACT: Climate change and biological invasions are major threats to biodiversity. In particular, these threats are predicted to influence terrestrial systems in the sub-Antarctic, where significant ecosystem responses to both have already been seen. In this thesis, the sub-Antarctic Prince Edward Island group is used as a model system in which to investigate key questions relating to climate change and invasive species impacts. The island group comprises two islands, Marion (MI) and Prince Edward (PEI), both of which are experiencing rapid warming, yet have different invasive assemblages and in consequence are experiencing different impacts. Variation in the patterns of invasive species richness and abundance and their underlying causes are matters of considerable ecological and conservation significance. While an increase in thermal energy availability typically results in an increase in species richness, the mechanisms underlying these patterns are poorly understood. In Chapter 2 of this thesis, these relationships are explored for springtails, an important component of the soil fauna on Marion Island. Energy explains a large amount of the spatial variation in indigenous and invasive springtail species richness. Disturbance thresholds and stressful temperatures are more important than increased population sizes in determining this variation in species richness. As both indigenous and invasive springtail species richness and abundance are strongly related to temperature, a warming climate could have far-reaching consequences for these organisms. In particular, invasive species are predicted to be at an advantage relative to indigenous species under warming conditions. One species where this seems especially likely, given its physiological responses to experimental warming and drying, is the large invasive tomocerid, Pogonognathellus flavescens. Determining whether this will be the case depends on understanding the factors underlying its range limits and abundance structure. Moreover, few studies have sought to distinguish the causal basis of abundance structure and range limits, particularly for invasive species. Thus, in Chapter 3, local microclimate variables and physiological tolerances of the invasive springtail, P. flavescens (a habitat generalist), are examined. The results suggest that the species should be widely distributed across a range of habitats on MI. However, the springtail is restricted to indigenous Poa cookii tussock grassland habitats in the southeast. The current range limits are set by dispersal limitation (i.e. contingent absences) whilst abundance structure is a function of variation in soil substrate quality. However, over time, the widening distribution of P. cookii, as a consequence of a major management intervention (the eradication of feral cats), may enable P. flavescens to colonise all suitable areas. In Chapter 4, the focus changes to what has been considered the third major response to climate change, along with range and phenological responses - changing animal body sizes. Body size is one of the most significant and obvious features of animals and is of considerable ecological and physiological importance. A prediction of the temperature-size rule (TSR) is that with warming, body size of the weevil species on both MI and PEI should decline. However, predation by mice of the weevils on MI should fundamentally affect the pattern of such change, causing it to differ from neighbouring PEI, indicating synergistic impacts between climate change and invasions. Analysis of a 24-year data set indicates a decline in the body size of all weevil species on PEI with increasing temperature. However, on MI, a negative relationship between mean annual temperature and body size is found only for Palirhoeus eatoni, a species not eaten by mice. A possible explanation for the positive relationships found for the other species could be due to higher metabolic demands imposed on mice in colder years than in warmer ones. Any increase in predation coupled with a preference for larger sizes, which the mice clearly show, would lead to a decline in the mean size of the weevil species. Due to the relationship between body size and metabolic rate and the importance of the weevils in the islands’ food webs, changes to the body size of these organisms could have significant consequences for the island ecosystems’ functioning. The thermal environment experienced by organisms also has a direct effect on survival, growth and reproduction. The physiological response of organisms to rapidly changing climates is therefore a primary concern. Organisms may respond to variable environmental conditions through phenotypic plasticity as well as behaviour. Chapter 5 of this thesis shows that of the weevil species and populations investigated on MI, most display phenotypic plasticity, the form of which is in keeping with the ‘Hotter is Better’ hypothesis. This could be due to rare extreme temperature events and the advantage for the performance curves to incorporate high temperatures experienced in the environment. Mismatches between thermal optima and preferred temperatures displayed by all species could mean that these weevils are well equipped to cope with warming conditions on MI unless the prediction of an increase of rare extreme events such as extreme temperatures is realised. Rapidly changing climates and an increase in the introduction of non-indigenous species are issues of major conservation concern. This has increased the significance of studies on the impacts of these threats. However, this thesis shows that to understand such processes, it is essential that an integration of disciplines be undertaken. This thesis thus adopts a multidisciplinary approach and highlights key issues associated with both climate change and biological invasions. The patterns and predictions of species and community responses to these environmental changes are complex. Moreover, predicting such responses is likely to be problematic, especially as multiple factors will change concurrently and how these factors might change is unclear. This highlights the importance of long-term records for understanding organism responses to such changes. Furthermore, impacts on indigenous species are likely to be exacerbated by the predicted increase in the rate of introductions with climate change. This makes the case for preventing the dispersal of invasive species to new areas all the more important. / AFRIKAANSE OPSOMMING: Klimaatsverandering en indringer spesies is belangrike bedreigings vir biodiversiteit. In besonder word voorspel dat hierdie bedreigings terrestriële sisteme in die sub-Antarktiese sal beïnvloed, waar beduidende ekosisteem reaksie aan beide reeds gesien is. In hierdie tesis word die sub-Antarktiese Prince Edward eiland groep as a model sisteem gebruik om belangrike vrae met betrekking tot klimaatsverandering en die impak van indringer spesies te ondersoek. Die eiland groep bestaan uit twee eilande, Marion (ME) en Prince Edward (PEE), wat beide versnellende verwarming ervaar, maar tog verskillende indringer samestellings het en vervolgens verskillende impakte ervaar. Variasie in die patrone van indringerspesierykheid en vollopheid en hulle onderliggende oorsake is van aansienlike omgewings en bewarings betekenis. Terwyl 'n toename in die beskikbaarheid van energie tipies lei tot 'n toename in spesierykheid, word die onderliggend meganismes van hierdie patrone swak verstaan. In Hoofstuk 2 van hierdie tesis, word hierdie verhoudings vir springsterte ondersoek, 'n belangrike komponent van die grond fauna op ME. Energie verduidelik 'n groot hoeveelheid van die ruimtelike variasie in inheemse en indringende springstert spesierykheid. Versteuringsdrempels en stressvolle temperature is meer belangrik as die toename in bevolking groottes in die bepaling van hierdie variasie in spesierykheid. Aangesien beide inheemse en indringende springstert spesierykheid en vollopheid sterk verwant is aan temperatuur, kan 'n verwarmende klimaat verreikende gevolge vir hierdie organismes hê. In die besonder word voorspel dat indringerspesies bevoordeeld sal wees relatief tot inheemse spesies onder verwarmende toestande. Een spesie waar dit veral blyk om geneig te wees, gegewe sy fisiologiese reaksie tot eksperimentele verhitting en uitdroging, is die groot indringer tomocerid, Pogonognathellus flavescens. Om te bepaal of dit die geval sal wees, hang af van die begrip van die onderliggende faktore van sy voorkomsgrense en vollopheidstruktuur. Daarbenewens is daar min studies wat gepoog het om te onderskei tussen die veroorsakende basis van vollopheidstruktuur en voorkomsgrense, veral vir indringerspesies. Dus, in Hoofstuk 3, word plaaslike mikroklimaat veranderlikes en fisiologiese toleransies van die indringer springstert, P. flavescens ('n habitat generalis), ondersoek. Die resultate stel voor dat die spesie wyd verspreid moet wees oor 'n verskeidenheid van habitatte op ME. Maar, die springstert is beperk tot inheemse Poa cookii polle grasveldhabitatte in die suidooste. Die huidige voorkomsgrense word daar gestel deur verspreidingsbeperking (dws voorwaardelike afwesighede), terwyl vollopheidstruktuur 'n funksie is van die variasie in die grond substraat kwaliteit. Maar, die uitbreidende verspreiding van P. cookii as gevolg van 'n groot bestuursingryping (die uitwissing van wilde huiskatte), kan P. flavescens in staat stel om alle geskikte gebiede te koloniseer met verloop van tyd. In Hoofstuk 4 verander die fokus na wat as die derde groot reaksie op klimaatsverandering beskou word, saam met voorkoms en fenologiese reaksies - veranderende diere liggaamsgroottes. Liggaamsgrootte is een van die beduidendste en mees voor die hand liggende eienskappe van diere en is van aansienlike ekologiese en fisiologiese belang. 'n Voorspelling van die temperatuur-grootte-reël (TGR) is dat met verwarming, liggaamsgrootte van die snuitkewerspesies op beide ME en PEE sal afneem. Hoe ookal, predasie deur muise van die snuitkewers op ME moet fundamenteel die patroon van sodanige verandering op PEE beïnvloed, wat sinergistiese impakte tussen klimaatsverandering en indringings aandui. Die ontleding van 'n 24-jarige datastel dui aan op 'n afname in die liggaamsgrootte van alle snuitkewer spesies op PEI met ‘n toename in temperatuur. Maar, op ME is 'n negatiewe verhouding tussen die gemiddelde jaarlikse temperatuur en liggaamsgrootte net gevind vir Palirhoeus eatoni, 'n spesie wat nie deur die muise geëet word nie. 'n Moontlike verduideliking vir hierdie positiewe verhoudings wat gevind is vir die ander spesies kan wees as gevolg van hoër metaboliese eise op die muise in kouer jare as in warmer jare. Enige toename in predasie, tesame met 'n voorkeur vir groter mates, wat die muise duidelik wys, sou lei tot 'n afname in die gemiddelde grootte van die snuitkewer spesies. As gevolg van die verhouding tussen liggaamsgrootte en metaboliese tempo, sowel as die belangrikheid van die snuitkewers in die eilande se voedselwebbe, kan veranderinge in die liggaamsgrootte van hierdie organismes beduidende gevolge op die eiland ekosisteme se funksionering hê. Die termiese omgewing wat deur organismes ervaar word het ook 'n direkte invloed op oorlewing, groei en voortplanting. Die fisiologiese reaksie van organismes op vinnig veranderende klimate is dus 'n primêre bron van kommer. Organismes kan reageer op veranderlike omgewingstoestande deur fenotipiese plastisiteit sowel as gedrag. Hoofstuk 5 van hierdie tesis toon dat van die snuitkewerspesies en bevolkings wat ondersoek is op ME, die meeste fenotipiese plastisiteit vertoon, die vorm wat in ooreenstemming is met die ‘Warmer is Beter’ hipotese. Dit kan wees as gevolg van seldsame uiterste temperatuur gebeure en die voordeel vir die prestasie kurwes om hoë temperature wat ervaar word in die omgewing in te sluit. Mismatches tussen termiese optima en voorkeur temperature vertoon deur alle spesies kan beteken dat hierdie snuitkewers goed toegerus is om die verhitting op ME te hanteer, tensy die voorspelling van 'n toename van seldsame uiterste gebeure soos uiterste temperature gerealiseer word. Vinnig veranderende klimate en 'n toename in die bekendstelling van nie-inheemse spesies is kwessies van groot bewarings kommer. Dit het die betekenis van studies oor die impak van hierdie bedreigings verhoog. Hierdie tesis toon egter dat om sulke prosesse te verstaan, dit noodsaaklik is dat 'n integrasie van die dissiplines onderneem word. Hierdie tesis aanvaar dus 'n multi-dissiplinêre benadering en beklemtoon die belangrike kwessies wat verband hou met beide klimaatverandering en biologiese indringing. Die patrone en voorspellings van spesies en die gemeenskapsreaksies op hierdie omgewingsveranderinge is kompleks. Verder, die voorspelling van sodanige reaksies sal waarskynlik problematies wees, veral omdat verskeie faktore gelyktydig sal verander en hoe hierdie faktore kan verander is onduidelik. Dit beklemtoon die belangrikheid van lang termyn rekords vir die begrip van organisme reaksies op sulke veranderinge. Verder, die impak van inheemse spesies is geneig om te vererger deur die voorspelde toename in die tempo van bekendstellings met klimaatsverandering. Dit maak die taak vir die bestuur van die voorkoming dat indringerspesies nuwe gebiede bereik al hoe meer belangrik.

<p align="justify"><i>Typologie des cours d’eau en Wallonie et caractérisation par la faune invertébrée</i><br>Vingt-cinq types de cours d’eau ont été définis en Wallonie d’après les termes de la Directive Cadre pour l’Eau en tenant compte des facteurs obligatoires et optionnels rassemblés sous trois critères : la taille (du « ruisseau » à la « très grande rivière »), la pente (faible, moyenne et forte), et cinq régions naturelles (la région limoneuse, le Condroz, la Famenne, l’Ardenne et la Lorraine belge, résumant les facteurs obligatoires altitude, latitude, longitude et géologie). Une approche par analyses multivariées appliquées à un grand nombre d’échantillons (listes taxonomiques) a permis de définir de façon plus précise certains types de rivières et de distinguer sept groupes typologiques montrant des assemblages faunistiques similaires.</p> <p align="justify"><i>Conditions de référence types et définition de l’état écologique des rivières en Wallonie à l’aide de métriques biocénotiques basées sur les invertébrés</i><br> Les listes faunistiques et les valeurs métriques de l’IBGN (Indice biologique global normalisé) issues du réseau d’évaluation de la qualité biologique en Wallonie ont été utilisées pour discriminer les types de rivières et pour définir les sites de référence, les conditions de référence et les limites des classes des états écologiques. Au sud du sillon Sambre et Meuse, impliquant quatre groupes typologiques de rivières, les valeurs de référence et la définition des états écologiques ont été basées et calculées sur un réseau de référence de sites de très bon état. Les « valeurs de conditions de référence » ont été définies par les médianes des métriques des sites de « très bon état ». Lorsque aucun site de très bon état n’était disponible, c’est-à-dire pour les groupes typologiques au nord du sillon Sambre et Meuse et pour la Meuse et la Sambre, les conditions de référence (ou le « potentiel écologique maximal ») et les limites de classes ont été basées sur des coefficients appliqués aux sites de « bon état » et sur jugement d’expert.</p> <p align="justify"><i>Exercice pilote d’inter-étalonnage</i><br> Cinquante échantillons ont été sélectionnés parmi les rivières du type d’inter-étalonnage européen R-C3 (petite taille, altitude moyenne, substrat siliceux) en Wallonie (correspondant aux « ruisseaux ardennais ») dans toute la gamme de qualités écologiques, du « très bon » au « mauvais » état. Chaque métrique de l’indice « Intercalibration Common Metrics » (ICM) a été comparée (par régression linéaire et polynomiale) aux valeurs de l’IBGN. La plus forte corrélation a été établie avec l’indice synthétique de l’ICM dont le R² très élevé (0,95) permet un inter-étalonnage précis et fiable. A un EQR (Equivalent Quality Ratio) de l’IBGN = 1 correspond un indice ICM très proche (= 1,004). En conséquence, la métrique « cote de l’IBGN » est proposée comme métrique pour l’évaluation de l’état écologique de la faune invertébrée en Wallonie.</p> <p align="justify"><i>Espèces exotiques et invasives</i><br>L’ouverture récente du canal à grand gabarit Main – Danube en 1992 et la navigation qui en résulte a permis à plusieurs espèces de macroinvertébrés ponto-caspiennes d’envahir successivement les bassins du Rhin et de la Meuse. De 1998 à 2000, le réseau de mesure a enregistré quatre nouvelles espèces exotiques dans la Meuse en Belgique : une polychète (<i>Hypania invalida</i>) et trois crustacés (<i>Hemimysis anomala, Dikerogammarus villosus, D. haemobaphes</i>). Peu avant, en 1995, le bivalve asiatique <i>Corbicula fluminea</i> et l’amphipode nord-américain <i>Crangonyx pseudogracilis</i> ont également été enregistrés pour la première fois. La dynamique des invasions a été étudiée et discutée.</p> <p align="justify">L’<i>état biologique actuel</i> (2000-2002) des masses d’eaux de surface en Wallonie et l’évolution des états biologiques sur une décennie (1990-2002) figurent dans l’étude et sont discutés. Une amélioration globale de la qualité de 6 % est enregistrée pour cette période. L’amélioration de la qualité se manifeste principalement pour les états « mauvais » et « médiocre » s’élevant à l’état « moyen ».</p> <b>Abstract</b> <p align="justify"><i>River typology in Wallonia and invertebrate fauna characterization</i><br>Twenty-five river-types in Wallonia were defined according to the Water Framework Directive taking into account obligatory and optional factors gathered in three criteria: the size (from “brook” to “very large river”), the slope (gentle, medium and strong) and five natural regions (Loess, Condroz, Famenne, Arden and Jurassic summarising the obligatory altitude, latitude, longitude and geology factors). A multivariate approach applied to a large amount of samples (i.e. taxa lists) led to give a more accurate definition of some river-types and to discriminate seven river-type groups exhibiting similar faunal assemblages.</p> <p align="justify"><i>Type-specific reference conditions and ecological status definition of rivers in Wallonia using invertebrate biocenotic metrics</i><br> Faunal lists and IBGN (i.e. "Standardized Global Biological Index IBGN") metric values, evolving from the biological quality assessment network in Wallonia, were used to discriminate the river types and to define the reference sites, the reference conditions and the status class limits. South of the axis made by the Sambre & Meuse Rivers, involving four river-type groups, reference values and ecological status definition were based and calculated on a reference network of sites of high status. The "reference condition values” were defined as the median values of the metrics in all “high status” sites. Where no site of high status was available, i.e. in the others river-type groups north of the same axis and in the Rivers Sambre and Meuse themselves, reference conditions (or maximum ecological potential) and class limits were based on coefficients applied to “good status” sites and on expert judgement.</p> <p align="justify"><i>Intercalibration pilot exercise</i><br> Fifty samples were selected from R-C3 rivers (i.e. small, mid-altitude, siliceous) in Wallonia (corresponding to the “Arden’s brooks”) showing the widest range of ecological quality from high to bad status. Each Intercalibration Common Metric (ICM) was compared (linear and polynomial regression) to IBGN scores. The highest correlation was found with the synthetic ICM index, whose high R² (0.95) allows accurate and reliable intercalibration. To IBGN EQR (i.e. Equivalent Quality Ratio) = 1 corresponds a very close ICM index value (= 1.004). Consequently, the metric IBGN score is being proposed to act as the metric for the assessment of the invertebrate fauna ecological status in Wallonia, Belgium.</p> <p align="justify"><i>Exotic and invasive species</i><br> The recent opening of the canal Danube – Main in 1992 and the subsequent navigation allowed several Ponto-Caspian macroinvertebrate species to invade successively the Rhine and the River Meuse basins. From 1998 to 2000, the monitoring network recorded four new alien species in the River Meuse in Belgium: one Polychaeta (<i>Hypania invalida</i>) and three Crustacea (<i>Hemimysis anomala, Dikerogammarus villosus, D. haemobaphes</i>). Earlier, in 1995, the Asian Bivalvia <i>Corbicula fluminea</i> and the North American Amphipod <i>Crangonyx pseudogracilis</i> were also recorded for the first time. The invasions’ dynamics were studied and discussed.</p> <p align="justify"><i>Present biological status</i> (2000-2002) of surface water-bodies in Wallonia and biological status evolution over a one-decade period (1990-2002) is included and discussed in the study. A global quality improvement of 6 % is recorded for the period. Quality improvement concerns mainly the “bad” and “poor” status raising up to “moderate” status.</p>

Sosnovskio barščio ir uosialapio klevo plitimo tyrimai buvo atliekami Pasvalio ir Kauno rajonuose. Tyrimo metu buvo nustatoma šių augalų plitimo ypatumai, efektyviausios kontrolės priemonės, invazijos agresyvumo lygmenys. Gauti tyrimai parodė, kad vanduo daro didesnę įtaką uosialapio klevo išplitimo atstumams nei vėjas, nes jų buvo aptinkama visame 10 km tirtos upės pakrantės ruože, o toliausiai vėjo pagalba atsiradę savaiminukai buvo aptikti iki 100 metrų nuo motininio medžio. Šie augalai dera gausiai, vidutiniškai vienas uosialapio klevo medis subrandina 70 tūkst. Sėklų. Sosnovskio barščio 1 m2 aptikta apie 7,5 tūkst. sėklų. Veiksmingiausia kontrolės priemonė uosialapiui klevui yra mažų savaiminukų naikinimas, nes kertant paaugusius medžius jie sėkmingai atželia iš kelmo ataugų. Sosnovskio barščio kontrolei, jų kasimas yra veiksmingiau nei purškimas, nes kasant atželia 45 % naikinamų augalų, o tik purškiant – 85 %. Apskaičiuotas invazyvumo lygmuo parodo, jog Sosnovskio barštis yra invazyvesnis nei uosialapis klevas. Uosialapio klevo invazyvumo lygmuo yra 0,42, o Sosnovskio barščio - 0,56. / The research on the spread of heracleum sosnowskyi and acer negundo was carried out in the regions of Pasvalys and Kaunas. The research focuses on the spread features of these plants, most effective control measures and the level of invasion. The results showed that water had larger influence on the spread of acer negundo than wind as some spontaneous trees were found in all 10 kilometers onshore area. The longest distance from the parent tree revealed to be approximately 100 meters. These plants fruit abundantly, approximately one mature tree of acer negundo produces 70 thousands of seeds. Heracleum sosnowskyi matures about 7.5 thousands of seeds / 1 m2. The most effective control measure of acer negundo is destroying spontaneous seedlings because cutting of the grown trees isn’t effective, they regrow from the stumps. For a control of heracleum sosnowskyi digging is more effective than spraying, because 45 % of the spontaneous seedlings regrow after digging while 85 % of them regrow after spraying. Calculated level of invasion shows that heracleum sosnowskyi is more invasive than acer negundo. A level of invasion of acer negundo is 0.42, heracleum sosnowskyi – 0.56.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Non-native species are recognized as a major component of global environmental change. Their ecological impacts are numerous and include the alteration of whole ecosystem processes as well as the loss of native biodiversity. As such, understanding the processes that drive the invasion of non-native species is essential for the control and management thereof. Numerous research approaches have been used to provide insight on the history and ecology of non-native species invasions. However, recent approaches employing molecular techniques have greatly helped in solving taxonomic issues associated with some of these species; identifying sources of invasions; and shedding light on colonization dynamics. Lantana camara, a globally invasive and highly variable species complex, is one of the most notorious plant invaders in South Africa. The species has been associated with negative impacts in agricultural areas, decreased invertebrate diversity, livestock mortality, and where it occurs along riparian areas- decreased water quality and obstruction to accessing water sources. This project aimed to review L. camara invasions in South Africa and to unravel patterns of spread in L. camara along the Sabie-Sand catchment in South Africa’s flagship protected area, the Kruger National Park, using a molecular approach. The findings of the first part of the study highlight that L. camara has successfully spread across South Africa with only four known introduction events, and this can be attributed to the species’ broad ecological tolerance, its use in the horticultural industry, and a variety of dispersal vectors (birds, humans and rivers). Furthermore, although sale of the species is prohibited in the country, it will continue to spread naturally and also has the potential to expand its distribution under changing climate scenarios. The second part of the study highlights that spread along the Sabie-Sand catchment is primarily river-driven and that the Sand tributary is the invasion source in the system. Because the Sand tributary originates outside the Kruger National Park, and only a small portion is under park management, the implications for spread are important. / AFRIKAANSE OPSOMMING: Nie-inheemse spesies word erken as 'n belangrike komponent van die globale omgewing verandering. Hulle ekologiese impak is talle en sluit in die verandering van ekosisteem prosesse asook die verlies van inheemse biodiversiteit. As sodanig, die begrip van die prosesse wat lei tot die inval van 'n nie-inheemse spesies is noodsaaklik vir die beheer en bestuur daarvan. Talle navorsingsbenaderings is gebruik om insig te gee oor die geskiedenis en ekologie van nie-inheemse spesies invalle. Onlangse benaderings soos die gebruik van molekulêre tegnieke, help in die oplossing van taksonomiese kwessies wat verband hou met 'n paar van hierdie spesies,in die identifisering van bronne van invalle, en om lig te werp op die kolonisasie dinamika. Lantana camara, 'n wêreldwye indringende en spesie kompleks, is een van die mees berugte plantindringer in Suid-Afrika. Die spesie is geassosieer met negatiewe gevolge in landbou gebiede, afgeneem ongewerwelde diversiteit, vee mortaliteit, en waar dit voorkom saam oewer gebiede - afgeneem kwaliteit van die water en obstruksie tot waterbronne. Hierdie projek is daarop gemik om om L. camara invalle in Suid-Afrika te hersien en patrone van verspreiding te ontrafel in L. camara langs die Sabie-Sand-opvanggebied in Suid-Afrika se vlagskip beskermde gebied, die Kruger Nasionale Park, met behulp van 'n molekulêre benadering. Die bevindinge van die eerste deel van die studie wys dat L. camara het suksesvol versprei oor die hele Suid-Afrika met slegs vier bekende inleiding gebeure, en dit kan toegeskryf word aan die spesie se breë ekologiese verdraagsaamheid, die gebruik daarvan in die hortologie bedryf, en 'n verskeidenheid van die verspreiding vektore (voëls, mens en riviere). Verder, hoewel die verkoop van die spesie in die land verbied word, sal dit natuurlik voortgaan om te versprei en het ook die potensiaal om uit te brui onder veranderende klimaat scenario's. Die tweede deel van die studie wys dat versprei langs die Sabie-Sandopvanggebied hoofsaaklik rivier-gedrewe is en dat die Sand sytak die inval bron is. Omdat die Sand sytak buite die Kruger Nasionale Park ontstaan, en slegs 'n klein gedeelte onder park bestuur is, is die implikasies vir verspreiding belangrik. / Financial support from the DST-NRF Centre of Excellence for Invasion Biology and the Working for Water (WfW) Programme through their collaborative project on “Research for Integrated Management of Invasive Alien Species” and Stellenbosch University’s Subcommittee B Young Researcher's Fund

In this thesis I review how Sargassum muticum (Yendo) Fensholt, an invasive alga from Asia, has spread globally due to human activities and describe how this species can affect seagrass ecosystems. Abiotic factors such as nutrient and substratum availability may facilitate the spread of S. muticum into Zostera marina L. meadows, but analyses of seawater nutrients, and sediment particle size and % organic content revealed no significant differences between experimental quadrats in seagrass meadows either with, or without the presence of S. muticum. Phenolic compounds were examined because they form the basis of defensive mechanisms in plants and algae, therefore any change in phenolic content may affect the ability of Z. marina to protect itself from disease, herbivory and invasive species through allelopathic interactions. Results from a four year field study and multiple annual laboratory experiments showed significant reductions (p = 0.034 and p = 0.002, respectively) in the caffeic and tannic acids equivalents content of Z. marina when in the presence of S. muticum. As the abundance of S. muticum increases, other changes in the physiology of Z. marina may occur including variations in growth rates, nutrient partitioning and chlorophyll fluorescence, but data from multiple laboratory experiments illustrated no significant differences in growth. Chlorophyll fluorescence analyses revealed significant differences between treatments with and without S. muticum (p = 0.008), but pairwise comparisons indicated these differences only occurred in 2008 (p &lt; 0.001). Significant differences were also found in nutrient partitioning amongst functional regions of the shoots (p = 0.024), but pairwise comparisons detected these differences between a biomass control treatment (ZZ: Zostera + Zostera) and the ZS (with S. muticum) and ZM (Z. marina on its own at a lower biomass per replicate) treatments (p = 0.013 and p = 0.019, respectively), but not between ZS and ZM. Previous in situ research has found negative effects of S. muticum presence on densities of kelp and other algae. Results from the long-term field study indicated significantly lower mean in situ Z. marina densities within the ZS treatment (p &lt; 0.001). Epibiota found living on the blades of Z. marina provide food for organisms within seagrass ecosystems and also create microhabitats for other species to occupy. Alterations in the abundances of epibiota and microhabitats formed could further modify seagrass ecosystems through shifts in timing of food availability, food preferences and microhabitats created. The long-term field study data revealed significantly lower epibiota abundances within the ZS treatment (p = 0.019), but differences in biomass between treatments were not detected. Changes in the biochemistry, physiology, vegetative physiognomy and epibiota assemblages of Z. marina revealed during experimental manipulations are presented and considered within the context of long-term seagrass survival in light of increasing S. muticum invasion.

L'acarien rouge de la tomate Tetranychus evansi (Tetranychidae) est considéré comme une espèce invasive à fort impact économique sur les cultures de solanacées. Il a été découvert pour la première fois en 1954 au Brésil, d'où il est probablement originaire. Historiquement, T. evansi a d'abord été signalé en Afrique et plus récemment en Europe et en Asie. L'objectif de cette thèse était de reconstruire les routes de colonisation de T. evansi et de dégager le scénario évolutif décrivant le mieux l'histoire de l'invasion. Nous avons d'abord analysé des échantillons collectés dans son aire actuelle de distribution, à l'aide des séquences d'un fragment du gène codant pour la sous-unité I de la Cytochrome Oxydase (COI) de l'ADN mitochondrial et de la région ITS1-5,8S-ITS2 de l'ADN nucléaire ribosomique. Les données soutiennent l'hypothèse d'une origine sud américaine de cette espèce et ont révélé que des événements d'invasions multiples et cryptiques ont eu lieu lors de la colonisation de l'Europe. L'invasion résulte de deux lignées génétiquement divergentes et originaires de deux régions géographiques distantes au Brésil. Ces deux lignées semblent avoir des potentiels invasifs contrastés. Elles s'hybrident au laboratoire ainsi que dans la nature. Grâce à 16 locus microsatellites que nous avons développés et utilisés comme marqueurs, nous avons déterminé les zones géographiques de cette hybridation. Nous avons également pu estimer des paramètres historiques de l'invasion et confronter différents scénarios d'introduction, par la comparaison de la composition génétique des populations récemment introduites avec celles de l'aire d'origine de T evansi, et par l'utilisation de la méthode d'inférence bayésienne (Approximate Bayesian Computation, ABC). Les résultats ABC contredisent partiellement le scénario d'invasion basé uniquement sur des données historiques. Ils suggèrent que T. evansi serait d'abord arrivé en Europe dans le sud de l'Espagne (en Andalousie) bien avant les signalements historiques. Ainsi, l'Andalousie semble avoir servi de source de colonisation pour des nouvelles zones en Afrique, d'autres régions méditerranéennes et d'Asie. Les résultats de cette thèse ouvrent des perspectives d'étude visant à comprendre pourquoi certaines populations d'une espèce allochtone réussissent à s'établir et à envahir un nouvel écosystème / The red tomato spider mite Tetranychus evansi (Tetranychidae) is regarded as an invasive species having an important economic impact on solanaceous crops. It was first discovered in Brazil in 1954, where it probably originated. Based on historical records, T. evansi was first reported in Africa and more recently in Europe and Asia. This work aims at reconstructing the colonization routes of T. evansi and identifies the scenario that best describes the evolutionary history of the invasion. To do this, we first analyzed samples collected from most parts of the world where the mite is currently known to occur. We used sequence variation of a fragment of the mitochondrial Cytochrome Oxidase I (COI) sub-unit I gene and the ITS1-5.8S-ITS2 of the nuclear ribosomal DNA. Our results were consistent with the hypothesis of a South American origin of this species. They also suggested that the invasion of south Europe resulted from multiple cryptic introductions from two genetically divergent lineages originated from two distant geographical regions in Brazil. These two lineages seem to have a differential invasive potential. Despite the high genetic divergence, crosses between mites stemming from the two lineages do occur both in the laboratory and in nature. Second, we used 16 microsatellite loci that we developed for this study and in association with Approximate Bayesian Computation (ABC) methods; we reconstructed the historical events of the cryptic invasion of the pest. ABC results challenge the invasion scenario captured by historical data only. They suggest that T. evansi first arrived to Europe in Southern Spain (Andalusia) long before historic records. Thus, Andalusia seems to have served as a source for colonization of new areas in Africa and other Mediterranean regions. The results obtained in this thesis provide an interesting framework to further study and understand why some populations of an exotic species might become invasive.

Biological invasions are one of the most important threats to global biodiversity and they were also found to negatively affect some bird species. Despite relatively large number of scientific studies dealing with the impacts of invasive plants on bird communities, their results are inconsistent, especially it is not clear how birds respond to increasing levels of expansion of invasive species in native species stands. Moreover, bird responses to plant invasions seem to depend on the ecological characteristics of individual bird species. This study contributes to elucidation of this problem; I investigated the impacts of black locust (Robinia pseudoacacia) invasion on bird communities in three types of forest stands with different levels of invasion: in stands containing solely the native oak (Quercus spp.), in partially invaded stands with different proportions of black locust and oak (mixed stands) and in pure black locust stands. Previous studies that examined birds in pure oak and pure black locust stands have found that they differ markedly in vegetation structure, but not in the total number of bird species. However, habitat specialists were associated with the oak stands, while generalists with the black locust stands. Therefore, I predicted that (1) the total species richness will be...