Adwine Vanslembrouck

• 13/01/2025
  
• 4 p.m.
• Venue: ITM, Campus Rochus, Aula Janssens, Sint Rochusstraat 43, 2000 Antwerpen
• ​Online PhD defence
• Supervisors: Herwig Leirs & Ruth Müller (ITM)
• Department of Biology

Abstract

Invasive Aedes mosquitoes, such as the tiger mosquito (A. albopictus) and the Asian bush mosquito (A. japonicus), are known vectors for various viruses. One of the most significant consequences of these invasive mosquito infestations in Europe is the outbreak of mosquito-borne diseases such as dengue and chikungunya. These invasive Aedes mosquitoes are known to spread to new areas due to climate change and globalization. Additionally, anthropization to the environment, such as urbanization and deforestation, are important drivers of their dispersal. These human interventions lead to biotic homogenization, resulting in reduced biodiversity. This results in a reduced competition from native mosquitoes and a decrease in predators that could limit the spread and establishment of invasive mosquitoes. Furthermore, there is an increase in insecticide resistance, making it more difficult to control mosquito populations. As a result, there is a growing need for alternative control methods, such as biological control.

This thesis investigates the ecological interactions, competition dynamics, and implications for vector control strategies, with a particular focus on the invasive Aedes mosquitoes and native Culex species. The research covers interspecific larval competition, thermophilic preferences, and arboviral infection risks, demonstrating how larval competition among mosquito species affects their susceptibility for arboviruses. We found that Aedes albopictus larvae benefit from competing with Culex hortensis, potentially amplifying arbovirus transmission risks. Additionally, larval interactions among Aedes albopictus, Aedes japonicus, and Culex pipiens reveal metabolic and behavioral adaptations that increase susceptibility to arboviruses like chikungunya and West Nile virus.

The insecticide resistance status in European Culex pipiens populations highlights the limitations of conventional mosquito control methods. Resistance to multiple insecticides, also found in Belgium, points out the urgent need for innovative alternative approaches, including biological control. In this research, the role of native predatory diving beetles as natural regulators of mosquito populations in Belgium was investigated, identifying Agabus bipustulatus as a highly effective predator for Aedes albopictus.

In sum, this thesis emphasizes the importance of ecological interactions in understanding mosquito-borne disease risk and in developing sustainable mosquito control strategies. By integrating insights from larval competition, arboviral risks, and alternative control methods, it contributes to a broader understanding of vector ecology and offers novel approaches to mitigate the public health impacts of invasive mosquitoes in Europe. ​ ​

Ignace Pelckmans

• 09/01/2025
  
• 5 p.m.
• Venue: Campus Middelheim, A.143
• Supervisor: Stijn Temmerman
• Department of Biology

Abstract

River deltas and estuaries are densely populated regions but face coastal flood risks due to extreme sea level events, particularly as climate change leads to rising sea levels and more instense storms. Nature-based strategies, such as the conservation and restoration of mangroves, are increasingly considered a cost-effective and sustainable addition to traditional flood defences. Cities such as Guayaquil (Ecuador), Ho Chi Minh (Vietnam) and Khulna (Bangladesh) all house millions of people but despite their growing exposure to coastal floods, the mangroves in between these cities and the sea have been largely lost to aquaculture. Yet, how the largescale conversion from mangrove to human land use affects the propagation of flood waves is still unknown. This thesis attempts to fill that knowledge gap by elaborating on how extreme sea levels are heightened or lowered when propagating through a tropical delta, and how this depends on the spatial properties of the complex network of mangroves, estuarine channels and human land use that is intrinsic to most tropical deltas. Hydrodynamic models allow the study of flood wave propagation over the tens to hundreds of kilometres that tropical river deltas typically cover. In this thesis, we present the setup, calibration and evaluation of a hydrodynamic model of the Guayas delta, Ecuador. The model demonstrated that the current mangroves in the delta effectively attenuate incoming extreme sea levels related to El Niño events and prevent the increase in sea level to amplify upstream. Furthermore, we show that the spatial locations of mangroves and aquaculture have a large impact on the attenuation of extreme sea levels with the strongest reduction in case mangroves are uniformly spread over the delta or concentrated upstream. During a field campaign, we measured high water level attenuation in a tropical Rhizophora forest, where aerial roots are several metres high, revealing attenuation rates up to 46 ± 9.8 cm/km, which are the highest attenuation rates ever recorded in a mangrove forest. With this thesis, we show how mangrove ecosystem properties and their spatial location within deltas affect the reduction of extreme water levels when propagating through the complex web of mangroves, channels and aquaculture, which is intrinsic to many tropical river deltas. Human infrastructure in the deltaic plain is often essential for the economic development of these regions, yet this thesis elaborates on where conversion from mangroves to human land use has minor effects on the reduction of high water levels.