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Keynote speakers

16th International Symposium on Aquatic Plants

Here are the Keynote speakers.

Keynote 1: Coetzee, Julie A. (Rhodes University, South Africa)


Bio sketch: Julie's research focuses on the ecology and biological control of invasive aquatic plants. She started working on biological control agents of water hyacinth in 1998, and has never looked back. Recently the focus of her work has expanded to include understanding invasions by submerged and emergent aquatic plants. As we have gained excellent control of the floating species, this new suite of species has taken advantage of these new habitats, threatening indigenous aquatic flora and fauna. Tackling these new problem plants is a challenge, but southern Africa will benefit from experience gained elsewhere in controlling these species, as well as pioneering new methods of control.

Title: Recent developments in control of aquatic macrophytes: insights from Sub-Saharan African

Abstract: Sub-Saharan Africa, and particularly southern Africa, has a long history of managing the establishment and spread of invasive floating macrophytes. The past thirty years of research and the implementation of biological and integrated control programmes has led to widespread control of these species in many degraded freshwater ecosystems. Such initiatives are aimed at restoring access to potable freshwater and maintaining native biodiversity. However, in recent years, there has been a decline in populations of floating invasive plants, and an increase in the establishment and spread of submerged and emergent invasive plant species, which poses significant threats to aquatic ecosystems. This talk highlights the vulnerability of Africa’s eutrophic systems to successful colonisation by this suite of new macrophytes following the successful biological control of floating invasive macrophytes, and explores a new regime shift in invasive populations partly driven by biological control. A more holistic approach to the control of invasive aquatic plants is required to ensure long-term ecosystem recovery and sustainability as Sub-Saharan Africa faces the pressures imposed by global climate change.

Keynote 2: Ludwig Triest (Vrije Universiteit Brussel & Université Libre de Bruxelles, Belgium)


Bio sketch: Prof. Ludwig Triest started studying aquatic plants in 1980. He obtained his PhD in 1986 and Aggregation Higher Education in 1991 on submerged macrophyte taxonomy and molecular-based population studies using isozymes, later followed by population genetics using DNA markers of various plant groups such as Ruppia, Stuckenia, Zannichellia, Najas, seagrasses, papyrus, mangroves and riparian willows. He has experience with European and tropical aquatic wetland and lagoon ecosystems. Practical skills are situated in the field of genetic diversity methodologies, aquatic ecology, monitoring, conservation and nature management. He taught Introduction to Biology and Molecular ecology for BSc students and specialized courses on River and Lake Ecology and on Conservation Genetics at MSc level. He (co-)authored more than 200 papers and supervised more than 30 PhD’s at the Vrije Universiteit Brussel.

Title: Genetic connectivity, migration history and dispersal distances in aquatic plants

Abstract: Dispersal of aquatic plants can occur through hydrological connectivity or through other land-based means. Macrophyte dispersal within rivers, within lakes or a series of lakes ensures successful and recurrent hydrochorous spread of vegetative and sexual propagules while aquatic plants in isolated water bodies rely largely on local recruitment, but also seed movement inputs from wind or biotic vectors. Thus, dispersal distances in aquatic plants are very context-dependent. Genetic markers such as nuclear microsatellites are widely applied and, given sufficient allelic and genotypic diversity, may provide interesting opportunities to infer genetic connectivity and isolation-by-distance (IBD). In this way, measures of genetic distance and geographic distance between aquatic sites are usually considered in exploratory methods (clustering and ordination), descriptive statistics of estimators of differentiation (Fst, Rst) under certain population-level assumptions, and in model-based clustering of individuals in subpopulations as gene pools (Bayesian approach). Nevertheless, inferring dispersal distances from genetic connectivity may be challenging, especially in aquatic plants, as they often show strong annual fluctuations in their population size, often causing founder events, bottle-necks, and inbreeding due to within-lake pollination between relatives. Distances over which pollen flow and seed flow can occur are usually interpreted in terms of IBD and significance of regression slopes. Despite an often significant IBD, the context-dependent dispersal of aquatic plants remains difficult to estimate due to their unknown underlying historical migration patterns during the Holocene. Haplotype networks and approximate Bayesian computation of entire chloroplast genomes allow testing demographic event models of a species and testing population origin models with an estimation of their divergence times and effective population sizes. Different approaches to infer historical migration, contemporary short-distance dispersal and long-distance dispersal were tested for various submerged and emergent macrophytes, providing guidance on the resilience of evolutionary significant units of populations across aquatic landscapes.







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