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Characterization of gene flow in Cylicodiscus gabunensis Harms and pollination dynamics in Central African timber tree species for sustainable exploitation

par Bhasin, Oriana
Président du jury Mardulyn, Patrick
Promoteur Hardy, Olivier J.
Co-Promoteur Vereecken, Nicolas
Publication Non publié, 2024-02-20

Thèse de doctorat

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Résumé :

This Ph.D thesis explores the complex dynamics of Central African rainforest ecosystems, focusing on the gene flow and insect pollination of canopy-emergent timber tree species such as Cylicodiscus gabunensis Harms and other important timber species. These selected species represent a wide range of flower types, indicative of diverse pollination syndromes. Additionally, some have been the subject of previous genetic research, providing insights into pollen dispersal distances. Special attention is given to C. gabunensis due to its significant importance and the challenges it faces, including low population density and limited natural regeneration within dense forests. Data on gene dispersal within its population are scarce, highlighting the need for immediate attention in developing sustainable management strategies.The first step was focused on developing 24 polymorphic microsatellite markers to study the genetic diversity, structure, and gene flow within C. gabunensis populations. This toolkit subsequently enabled an in-depth exploration of the complex interactions influencing regeneration in C. gabunensis, including human activities, mating systems, and seed/pollen dispersal processes. Spatial and genetic analyses provided insight into population-specific characteristics, highlighting the necessity for context-specific and nuanced management strategies to ensure the long-term sustainability of the species.The focus then shifts to the often-overlooked role of insect-mediated pollination in tropical canopy trees. Exploring insect pollination within African canopy-emergent tree species using camera observations, the subsequent section offers insights into a diverse range of floral traits and pollination syndromes. This chapter challenges conventional assumptions regarding flower size, pollinator size, and pollen dispersal distances while also indicating that cross- pollination is not expected to be limited under selective logging based on extensive estimates of pollen dispersal distances.Addressing the lack of a standardized method to monitor insect pollination in tropical canopy trees, traditional and more innovative approaches —such as insect sampling, canopy camera observations, and DNA barcoding— to unveil the intricate dynamics of pollination within five canopy-emergent timber species. The findings underscore the importance of comprehensive data collection and a multifaceted approach to enhance our understanding of insect pollination for informed decisions in support of sustainable management practices.Finally, a citizen science initiative was implemented to tackle the difficulties of analyzing large datasets collected from continuous camera recordings. The reliability of a structured citizen science protocol for identifying arthropod flower visitors in African canopy ecosystems was also evaluated, and potential improvements were proposed, such as integrating image recognition software for data analysis.In the concluding section, a comprehensive synthesis was presented that summarizes the main findings and implications of the research conducted. The synthesis highlights the importance of context-specific management strategies in ensuring the long-term sustainability of species, particularly in the face of environmental changes. It also underscores the complex factors affecting insect-mediated pollination and reproductive potential of Central African timber tree species and the need for comprehensive data collection and integrated approaches.This Ph.D thesis collectively contributes to a deeper understanding of Central African rainforest ecosystems, elucidates the reproductive potential and gene flow of C. gabunensis, and underscores the pivotal role of insect pollinators. These insights are invaluable for informed decision-making in support of sustainable forest management and biodiversity conservation efforts.