Browsing by Author "Minoarivelo, Henintsoa Onivola"
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- ItemThe eco-evolutionary dynamics of mutualistic networks: from pattern of emergence to stability(Stellenbosch : Stellenbosch University, 2016-03) Minoarivelo, Henintsoa Onivola; Hui, Cang; Stellenbosch University. Faculty of Science. Dept. of Mathematical Sciences. Centre for Invasion Biology.ENGLISH ABSTRACT: Mutualistic interactions, such as the interactions between flowering plants and their pollinators are ubiquitous in nature. A community in which members are involved in multiple mutualistic interactions forms a mutualistic network. The structure of such a network exhibits well-organized pattern, suggesting that complex ecological and evolutionary processes underlie the assembly of mutualistic networks. Although significant development has recently been achieved in uncovering the structural patterns of mutualistic networks, understanding ecological and evolutionary mechanisms that contribute to the emergence of these patterns and the overall ecological and evolutionary stability of mutualistic communities stays a challenge. Addressing this challenge is the aim of this thesis. We develop a mathematical and simulation model of the ecological dynamics of population densities and the evolutionary dynamics of functional traits of a mutualistic community to deal with the problem. Based on the fact that ecological and evolutionary mechanisms are interdependent, we use the framework of adaptive dynamics. We found that the wellorganized structural patterns observed in mutualistic networks such as a high nestedness and high modularity can emerge when interactions are trait-dependent and the accessibility to intra and cross trophic resources controlled. Moreover, we found that mutualism plays a determinant role in sustaining evolutionary stability and the productivity of the community. However, the evolutionary trajectories of functional traits in a mutualistic community can experience bistability and bifurcation when mutualistic interactions are highly specialized. In this case, mutualism often creates opportunity empty niche for invasion. Biological invasions targeting a specific peak of empty niche could lead to a strong directional selection in the community. In addition, an introduced species that has a trait different from those of native species and a level of interaction specialization similar to that of the native species is more likely to invade. The structure of the recipient network, such as its nestedness or modularity, is not a primary determinant of invasibility compared to other measurements of network stability such as robustness, resilience and disruptiveness. Consequently, we argue that the interplay of ecological and evolutionary processes through trait-mediated interactions can shed light on important questions in mutualistic networks.
- ItemInvading a mutualistic network : to be or not to be similar(Wiley Open Access, 2016) Minoarivelo, Henintsoa Onivola; Hui, CangBiological invasion remains a major threat to biodiversity in general and a disruptor to mutualistic interactions in particular. While a number of empirical studies have directly explored the role of invasion in mutualistic pollination networks, a clear picture is yet to emerge and a theoretical model for comprehension still lacking. Here, using an eco-evolutionary model of bipartite mutualistic networks with trait-mediated interactions, we explore invader trait, propagule pressure, and network features of recipient community that contribute importantly to the success and impact of an invasion. High level of invasiveness is observed when invader trait differs from those of the community average, and level of interaction generalization equals to that of the community average. Moreover, multiple introductions of invaders with declining propagules enhance invasiveness. Surprisingly, the most successful invader is not always the one having the biggest impact on the recipient community. The network structure of recipient community, such as nestedness and modularity, is not a primary indicator of its invasibility; rather, the invasibility is best correlated with measurements of network stability such as robustness, resilience, and disruptiveness (a measure of evolutionary instability). Our model encompasses more general scenarios than previously studied in predicting invasion success and impact in mutualistic networks, and our results highlight the need for coupling eco-evolutionary processes to resolve the invasion dilemma.
- ItemProbabilistic modelling of the evolution of ecological interaction networks(Stellenbosch : Stellenbosch University, 2011-12) Minoarivelo, Henintsoa Onivola; Sheffler, Konrad; Hui, Cang; Stellenbosch University. Faculty of Science. Dept. of Mathematical Sciences.ENGLISH ABSTRACT: In any ecological system, organisms need to interact with each other for their survival. Such interactions form ecological networks which are usually very complex. Nevertheless, they exhibit well de ned patterns; these regularities are often interpreted as products of meaningful ecological processes. As the networks are evolving through time, biological evolution is one of the factors that affects ecological network architecture. In this work, we develop a mathematical model that represents the evolution through time of such ecological interaction networks. The problem is approached by modelling network evolution as a continuous time Markov process, in such a way that the interactions in which a parent species is involved are potentially inherited by its descendant species. This approach allows us to infer ecological parameters and ecological network histories from real-world network data, as well as to simulate ecological networks under our model. While ecologists have long been aware of the in uence of evolutionary processes in shaping ecological networks, we are now able to evaluate the importance of such in uence.