Phylogeny, biogeography, and breeding system evolution in Moraceae

Abstract : Angiosperms are the most diversified clade of extant plants and are exceptionally species-rich in tropical regions. In this thesis, I investigated breeding system evolution and biogeographic history in the family Moraceae, which I used as a model clade to understand the origin and evolution of diversity of angiosperms. In Chapter I, I reconstructed and calibrated a new dated phylogenetic tree for Moraceae as a whole. I then used this tree to reconstruct ancestral states of breeding systems in Moraceae and Ficus. The crown group ages of Moraceae and Ficus were estimated in the Cretaceous and in the Eocene, respectively. Dioecy was inferred as the ancestral breeding systems of Moraceae, with several subsequent transitions to monoecy, including in Ficus. This result suggests that dioecy is not necessarily an evolutionary dead end. In Chapter II, I reconstructed a dated phylogenetic tree for tribe Dorstenieae, mainly distributed in tropical regions, with a new data set of nuclear genomic data generated with a Hyb-Seq approach. Biogeographic history was then reconstructed using dispersal-extinction-cladogenesis models. The crown group ages of Dorstenieae and Dorstenia were estimated in the Cretaceous and in the Cretaceous/Paleocene period, respectively. Two long-distance dispersal events from continental Africa to South America occurred in the Cenozoic (Dorstenia and Brosimum s.l.). In Chapter III, I tested the climatic niche difference (temperature and precipitation) between the two breeding systems (monoecy and gynodioecy) in Ficus using a new dataset of cleaned spatial occurrence records and breeding systems for 183 species. I used two comparative approaches: generalized estimating equations (GEE) and generalized linear models (GLM). A positive relationship between precipitation and gynodioecy was supported by GLM, but not GEE analyses, and no relationship between temperature and breeding systems was supported by either method. Higher dispersal ability and the potential for self-fertilization may explain why monoecious species of Ficus have been able to colonize and survive in drier environments. This thesis highlights the potential of phylogenetic comparative methods and phylogenomic data to address questions of breeding system evolution and biogeography in Moraceae, and opens up several important new perspectives worth investigating in other plant clades, such as a relationship between breeding system and climatic niche.
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Qian Zhang. Phylogeny, biogeography, and breeding system evolution in Moraceae. Plant breeding. Université Paris-Saclay, 2019. English. ⟨NNT : 2019SACLS205⟩. ⟨tel-02268575⟩

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