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Examining the role of dispersal in species diversification and evolution through the lens of a prevalent tree species of the Central African rain forests, Staudtia kamerunensis Warb.

par Matvijev, Katarina
Président du jury Mardulyn, Patrick
Promoteur Hardy, Olivier J.
Publication Non publié, 2023-06-14

Thèse de doctorat

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Résumé :

The role dispersal has for species diversification and dynamics of angiosperms is a topic that has been extensively discussed. However, studies have seldom attempted to investigate this on at a wider range of species scales. Thus, the aim of this thesis was to explore the effect dispersal has on diversification and species dynamics ranging from the family level down to local populations, using Staudtia kamerunensis Warb. (Myristicaceae) as our biological model. We collected genetic samples of S. kamerunensis and other Myristicaceae from multiple herbaria and from the field (Gabon and the Democratic Republic of Congo), and extracted their total genomic DNA to use in molecular analyses. We used a variety of sampling schemes, with an aim of obtaining a wider range of information. We performed Sanger sequencing, microsatellite genotyping and genome skimming. In Chapter 1, we explored the biogeography of Myristicaceae. We then reconstructed a dated phylogeny using plastid sequences and Bayesian inference. We found that the family has a Miocene crown age, with the African species bring the basal group. We consider that the family reached its current disjunct distribution at least partially through long-distance transoceanic dispersal.In Chapter 2, we reconstructed the plastid lineages of S. kamerunensis and their historical spread throughout Central Africa and estimated the crown age of the species. We identified five plastid lineages, and a stark difference in genetic diversity between the western and eastern lineages. We estimate that S. kamerunensis reached its current geographic range fairly recently and rapidly, indicating a potentially high dispersal capacity.In Chapter 3, we investigated the intraspecific genetic diversity of S. kamerunensis through the use of microsatellite markers and Sanger sequencing. We found traces of past fragmentation and identified five genetic clusters. We found that gene flow between genetic clusters is uninterrupted, with pollen likely being a strong contributor to admixing.Finally, in Chapter 4, we performed a parentage analysis on two populations of S. kamerunensis from Gabon using microsatellite markers. Additionally, we investigated the population structure and genetic diversity. We found that population structure and seed dispersal depend on the type of landscape.Overall, we conclude that seed and pollen dispersal shape the dynamics of S. kamerunensis at several scales. Moreover, we found that the extent of seed and pollen dispersal will also depend on the type of landscape and the presence of conspecifics. At the family level, we also found that long-distance dispersal likely contributed to the spread and diversification of Myristicaceae.