Le frelon Vespa velutina, est une espèce invasive introduite en France il y a une dizaine d’années. Cet Hyménoptère social chasse de nombreux insectes, et plus particulièrement des abeilles, exerçant une forte pression de prédation sur l’entomofaune. Son établissement en Europe est donc susceptible d’avoir un impact néfaste sur les activités humaines et sur la biodiversité locale. L’olfaction joue un rôle central dans la biologie du frelon, que ce soit pour la communication intraspécifique (phéromones) ou la recherche de nourriture. Pour limiter l’impact de V. velutina, une stratégie prometteuse serait d’interférer avec son comportement olfactif. Nous avons donc cherché à acquérir une meilleure connaissance du système olfactif des frelons ainsi que des signaux chimiques impliqués dans leur comportement de prédation. Nous avons tout d’abord décrit et comparé l’organisation du système olfactif des différentes castes d’une colonie de frelons. Le premier centre olfactif du cerveau, le lobe antennaire, est constitué d’unités morphologiques et fonctionelles, les glomérules. Nous avons démontré l’existence de glomérules hypertrophiées (macroglomérules), potentiellement spécialisées dans la détection des phéromones sexuelles, chez les mâles. Nous avons également observé des similarités neuroanatomiques frappantes dans l’organisation du lobe antennaire chez des Hyménoptères de familles différentes (fourmis, abeilles, frelons), permettant de reconstruire une partie de l’histoire évolutive de cette structure, au sein de cet ordre. En particulier, nous avons démontré l’homologie d’un groupe de glomérules impliqué dans le traitement des hydrocarbures cuticulaires, signaux de reconnaissance intraspécifique, chez les frelons et les fourmis. Ce système a pu représenter une préadaptation pour l’apparition de comportements sociaux dans ces familles. De plus, nos résultats ont montré que le nombre de glomérules dans ce système varie fortement chez différentes espèces de frelons, probablement en relation avec les différents niveaux de sympatrie dans lesquels vivent ces espèces. Le lobe antennaire des frelons présente ainsi des adaptations concernant aussi bien le nombre de glomérules que leurs volumes respectifs. Enfin, nous avons effectué des essais comportementaux pour déterminer quels composés odorants sont impliqués dans l’attraction de V. velutina envers les ruches d’abeilles domestiques. Nos résultats suggèrent que les ouvrières de frelon sont sélectivement attirées par des odorants indiquant la présence de ruches, dont des phéromones d’abeille. Ces résultats permettent d’envisager le développement de stratégies de piégeage utilisant des appâts olfactifs spécifiques. / The hornet Vespa velutina is an invasive species introduced from China to France about 10 years ago. This social hymenoptera preys on numerous insects species, but predominantly from honeybee colonies, hence exerting a stong predation pressure on insect fauna. Its etablishment to Europe can have strong detrimental effects on human activities and local biodiversity. Olfaction plays a central role in the biology and behavior of hornets, for both intraspecific communication or food search. To limit the impact of V. Velutina, a promising strategy would be to interfere with its olfactory behaviors. We thus aimed to acquire a better knowledge on the olfactory system of hornets and on the chemical signals involved in their predatory behavior. We first described and compared the organization of the olfactory system of the different castes of hornets. The first olfactory processing center, the antennal lobe, consists of morphological and functional units, the glomeruli. We have demonstrated the existence of enlarged glomeruli (macroglomeruli), potentially specialized in the detection of sex pheromones in males. We also observed striking neuroanatomical similarities in the antennal lobe organization of different Hymenoptera families (ants, bees, hornets) allowing to retrace part of the evolutionary history of this structure within that insect order. In particular, we demonstrated the homology of a glomerular cluster involved in the processing of cuticular hydrocarbons (intraspecific recognition signals) among hornets and ants. This systsem could be a preadaptation for the emergence of social behaviors in these families. In addition, our results showed that the number of glomeruli within this system varies across hornet species, probably due to the different sympatry levels these species experience. The hornet antennal lobe presents adaptations both in the number and the volume of glomeruli. Finally, we performed behavioral tests to identify odor compounds involved in the attraction of V. Velutina towards bee hives. Our results suggest that workers are selectively attracted to olfactory cues indicating the presence of hives, including some honeybee pheromones. These results allow considering the development of trapping strategies using specific baits.

Pannes are rare intradunal wetlands. Though small, they are known to exhibit extremely diverse and sensitive vegetation and are home to a number of reptile and amphibian species. In the United States, pannes are known to occur only around the Great Lakes Basin and Cape Cod. At Indiana Dunes National Lakeshore, the fifteen known pannes have an unusually large variety of plant species for such a small geographic area and provide habitat for plant species found nowhere else in Indiana. However, these sensitive ecosystems have been exposed to over a century of atmospheric pollutants from the surrounding steel and coal industries. Since 1986, the native vegetation of the area is slowly being replaced by invasive species like Phragmites australis and Typha spp. This study attempts to explain the shift in vegetation. Pannes in two other locations, at a distance from the industrial complex, were used as control sites as they were not expected to be exposed to the same levels of heavy metal concentrations. Four of the fifteen pannes at the Indiana Dunes National Lakeshore, two of the four pannes at Sleeping Bear Dunes National Lakeshore, Michigan, and two of the three pannes at Warren Dunes State Park, Michigan, were studied, resulting in a total of eight pannes. The pannnes were stratified and sampled by hydroperiod. Surface soil samples and sediments at depth, were recovered from each of the pannes considered in this study and analyzed for heavy metal, phosphorus, carbon and nitrogen content. Results show that high levels of organic matter coupled with high nutrients and high metals, in the soil, are a combination that may be considered a risk factor for future invasion of pannes by invasive species. It appears to be difficult for the native vegetation to deal with the high metals and high nutrients which are deleterious to the native vegetation and facilitate establishment of invasive vegetation which is more tolerant to the altered geochemical conditions.

No description available.

Dealing with invasive alien species (IAS), have become a more common problem for themunicipalities of Sweden over the past years. IAS is one of the largest threats to biologicaldiversity and the spread of invasive alien plants is caused by transportation, travel, climatechanges but also infrastructure projects. Thus, the risk of spreading them must be dealt withearly in the progress of handling soil masses. This study examines if recommended routines(with the aim of reducing the risk of spreading invasive plants) are incorporated inmunicipalities and how well they function. It further examines if routines for invasive plantsare related to the size of the municipality, due to differences in economy and resources. Aform was sent to all 290 municipalities in Sweden and 132 answered. The results show thatmany of the recommended routines are not well incorporated across municipalities. Routineswith demands of knowledge about IAS to coworkers or entrepreneurs is less functioning thanroutines of intern information, such as where invasive plants are established on propertiesthat’s own by municipalities. Results show that available resources and economy due to sizeof the municipalities do not influence the level of incorporation of routines. It’s warranted formunicipalities to establish functioning routines within the organization to prevent increasingspread of invasive alien plants in an early stage. The issue should be addressed in decisionsmade by politicians to confirm the level of priority since the benefits of prevention is higherthan benefits of elimination and eradication.

Thesis (M. Sc. (Botany)) -- University of Limpopo, 2022 / Nature reserves are reservoirs for biodiversity. Their very purpose is to preserve indigenous fauna and flora and thus protect associated ecosystem services. The Schuinsdraai Nature Reserve of rural Sekhukhune District, Limpopo Province, is the focus of this study. Sekhukhune District is predominantly rural, with limited economic opportunities but rich mineral resources, the mining of which negatively impacts biodiversity. The Sekhukhune Centre of floristic endemism falls within this district and the nature reserve is thus an important factor in safeguarding a representative section of this floristic center. The veld type present in the reserve is central sandy bushveld. Although mining is prohibited within the reserve, invasive alien plants or (IAPs) pose as high a threat to biodiversity as does mining. The spread of IAPs in nature reserves is harder to control than mining which is prohibited outright whereas IAP spread is automatic and insidious. The management of IAPs is of concern to the government of South Africa and is an ongoing process. Rural areas and the nature reserves within them, such as the Schuinsdraai Nature Reserve, are often under studied or under managed with regards to IAPs. This study supplements the available but scarce data on IAPs for Schuinsdraai Nature Reserve. The Schuinsdraai Nature Reserve is dominated by the Central Sandy Bushveld vegetation type. Rainfall is on average 470 mm per year and mean annual temperature varies from 24 ˚C in the summer, to 14 ˚C in the winter. The topography includes mountains, hills, plains, and the Flag Boshielo Dam. The aims of the study were to establish the presence and extent of IAPs in the Schuinsdraai Nature Reserve and to determine whether the IAPs present negatively affect the biodiversity. Road-side inspections, road surveys and line transects were used to investigate presence and extent of IAPs. Modified Braun-Blanquet quadrates were used to compare the effect of the most prevalent IAPs on the plant biodiversity in the Schuinsdraai Nature Reserve. Quadrates were positioned in areas heavily infested by species of IAPs and these areas compared with untransformed areas within 10 m of the infested quadrates. Species richness, species evenness and v biodiversity indices were calculated for transformed (control) areas compared with infested areas. Roadside inspections and road surveys indicated the presence of IAPs. They revealed that most IAPs were present on the eastern side of the nature reserve closest to areas most visited by tourists. Roads and the movement of people therefore affect the spread of IAPs within the Schuinsdraai Nature Reserve. The four most prevalent species identified from roadside inspections and road surveys were: Opuntia stricta, Cylindropuntia fulgida, Cereus jamacaru and Boerhavia diffusa. Opuntia stricta had the greatest negative effect and was also the most prevalent IAP on the Schuinsdraai Nature Reserve. The number of IAPs per transect observed in the area where access was unlimited was significantly higher than where access was limited. Opuntia stricta was the IAPs exhibiting the most significant (.00057) impact on species richness and species diversity and, where funds are limited, these should be targeted for eradication rather than other IAPs. From the results obtained, management recommendations were tabled including the most important, which is to clearly demarcate areas where public movement should be restricted, and meticulously patrol areas which are open to the public and remove IAP’s immediately. In conclusion, IAPs are present and do cause deleterious effects on species richness, diversity and evenness within the Schuinsdraai Nature Reserve, however, the strict management of anthropogenic influences should be implemented to control their spread and increase.

付記する学位プログラム名: 社会を駆動するプラットフォーム学卓越大学院プログラム / 京都大学 / 新制・課程博士 / 博士(農学) / 甲第25317号 / 農博第2583号 / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 北島 薫, 教授 小野田 雄介, 教授 井鷺 裕司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Thesis (DSc)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: No abstract available / AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 112-121). Also available on the World Wide Web.

No description available.

Master of Science / Department of Biology / Jesse B. Nippert / In 1902, President Theodore Roosevelt signed and enacted the Reclamation Act, which would fundamentally alter the lowland hydrology of the arid southwest over the next century. Flow regulations, groundwater pumping, damming, and river channel changes have led to decreases in water table heights and periodic overbank flooding, and subsequently, increased soil salinity in the arid Southwest. During this period, native riparian tree species have declined significantly and an invasive tree species, Tamarix ramosissima, has increased in abundance and distribution. Increases in soil salinity negatively impact the physiology of native riparian tree species, but the impacts of soil salinity on Tamarix physiology are incompletely known. I studied the impact of increasing soil salinities on the physiology of Tamarix in both field and controlled environments. I first studied the impacts of increasing soil salinities on Tamarix physiology at two semi-arid sites in western Kansas. I concluded that physiological functioning in Tamarix was maintained across a soil salinity gradient from 0 to 14,000 ppm illustrating robust physiological responses. Using cuttings from Tamarix trees at both sites, I subjected plants to higher NaCl concentrations (15,000 and 40,000 ppm). Tamarix physiology was decreased at 15,000 ppm and 40,000 ppm. Tamarix physiological functioning was affected at the induction of treatments, but acclimated over 30-40 days. These results reveal a threshold salinity concentration at which Tamarix physiological functioning decreases, but also illustrate the advantageous halophytic nature of Tamarix in these saline environments. Many arid and semi-arid environments are predicted to become more saline, however, results from both studies suggest that increasing salinity will not be a major barrier for Tamarix persistence and range expansion in these environments.