Phylogeography and population genomics of Pitcairnia lanuginosa (Bromeliaceae)

Author(s)

Bárbara Simões Santos Leal

• Document type: Doctoral Thesis
• Press: Rio Claro. 2019-01-10.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Rio Claro
• Defense date: 2018-12-07
• Advisor: Clarisse Palma da Silva

Abstract

The Neotropics harbors high levels of taxonomic, phylogenetic and functional diversity, even comparing to other tropical regions. The studies on processes driving diversification of intra-specific lineages and the origin of new species are essential to interpret the high levels of biodiversity found in this region. Here, we aimed to describe patterns of intra-specific diversification, and infer processes and mechanisms driving the Neotropical diversification by reviewing plant phylogeographic studies in Brazil (CHAPTER 1), and by performing empirical studies using a wide-spread, patchy distributed species, Pitcairnia lanuginosa, as a study model (CHAPTERS 2 and 3). In the first chapter, we reviewed and synthesized the knowledge from 41 previously published studies. In summary, we showed that Pleistocene climatic oscillations distinctly affected plants living in contrasting vegetation types within each biome. Despite past climate, these studies pointed that edaphic conditions and geographical barriers (such as mountains and rivers) have also influenced plant evolution patterns in this region. In the second chapter, we employed traditional molecular markers (sanger sequencing and microsatellites genotyping) and species distribution models (SDMs) to test the role of historical demographic processes on neutral genetic variation and verify the existence of lineages within P. lanuginosa, using a phylogeographic approach. Our data pointed to low genetic diversity within populations, and high genetic structure among populations within the species, which implies drift as a major force shaping the species evolution. Moreover, results evidenced two distinct P. lanuginosa lineages occupying the Brazilian Cerrado and the Central Andean Yungas that have likely diverged through dispersal from the Cerrado to the Central Andean Yungas. Although our SDMs showed a slight expansion of suitable range for P. lanuginosa during the Last Maximum Glacial, Pleistocene climatic oscillations seem to have played only a minor role on the diversification of the species, as molecular data show a signature of older divergence, followed by persistence in riparian forests. Finally, at the third chapter, we integrated hundreds of SNP markers defined through double-digest restriction-site associated DNA sequencing (ddRAD-Seq) and population-level phenotypic data, to infer the relative role of natural selection and genetic drift on the high genetic structure of P. lanuginosa. Results confirmed the relevant role of drift and suggested that selection plays an additional role on genetic differentiation despite strong drift effect. Among the tested phenotypic traits, only two traits associated to drought tolerance are potentially under selection. Diversification patterns of forbs associated to patchy mesic habitats, such as P. lanuginosa, add important information on past connections between biomes and may help to outline the biogeographic history of South America. Although studying biodiversity in the Neotropics remains challenging, and our knowledge is still limited by some obstacle to biodiversity research, increasing independent information from a wide variety of organisms have the potential to elucidate the complex processes driving the Neotropical biota. (AU)

• FAPESP's process: 14/08087-0 - Phylogeography, adaptive variation and reproductive biology of Pitcairnia lanuginosa complex (Bromeliaceae)
• Grantee: Bárbara Simões Santos Leal
• Support Opportunities: Scholarships in Brazil - Doctorate