Evolution of the Asian Palmate group of Araliaceae and its relationship with climate across geographic and temporal scales
- Autores: Angélica Gallego Narbón
- Directores de la Tesis: Virginia Valcárcel (dir. tes.), Mario Fernández Mazuecos (dir. tes.)
- Lectura: En la Universidad Autónoma de Madrid ( España ) en 2024
- Idioma: inglés
- Número de páginas: 292
- Títulos paralelos:
- Evolución del grupo asíatico de hojas palmeadas de la familia Araliaceae y su relación con el clima a través de varias escalas geográficas y temporales
- Tribunal Calificador de la Tesis: Ricarda Riina (presid.), Isabel Draper (secret.), Juan Viruel (voc.)
- Programa de doctorado: Programa de Doctorado en Biología por la Universidad Autónoma de Madrid
- Materias:
- Enlaces
- Tesis en acceso abierto en: Biblos-e Archivo
- Resumen
Understanding the factors determining why biological diversity is unequally distributed across lineages and across the Earth is one of the most important goals of evolutionary biology. Several biotic and abiotic factors and their interaction have been considered drivers of plant diversification across spatial and temporal scales. These include functional traits relevant for survival and/or reproduction (e.g., flower and fruit characteristics related to pollination or dispersal), spatiotemporal environmental variation (e.g., climatic heterogeneity and geographic barriers), and interactions between plants (e.g., hybridization and competition) among others. The relevance of each of these factors as a driver of evolution is lineage- and time-dependent. In this thesis, we focus on the evolutionary history of the Asian Palmate group (AsPG) of the plant family Araliaceae, an ideal study system to explore the influence of environmental variability, functional traits, and hybridization in evolution and diversification. In this regard, the AsPG exhibits a worldwide distribution with higher generic and species diversity in tropical latitudes and lower in temperate latitudes, and a great diversity in functional traits. Previous research pointed to an early evolutionary radiation coupled with hybridization between generic lineages at the early steps of the evolution of the clade, although phylogenetic resolution has been limited thus far. In this thesis, we aim to study how the intersection between climate and geography have shaped the evolution of the AsPG across several geographic and temporal scales, from the divergence of the main clades and genera to the speciation and population differentiation in the temperate genus of ivies (Hedera). We chose the genus Hedera as our study group at a narrow evolutionary scale because of its wide geographic distribution covering a wide climatic variability in Asia, continental Europe, northern Africa, and Macaronesia, and because of its complex evolutionary history marked by several polyploidization events. For each of the evolutionary scales analyzed we have used a different next-generation sequencing technique (Hyb-Seq for the AsPG and genotyping-by-sequencing, GBS, for Hedera) to obtain highly resolved time-calibrated phylogenies and conduct comparative analyses using geographic, climatic, functional, and chromosomal data. Climatic data were obtained from online repositories and field work, while functional and chromosomal data were obtained from herbaria, field work and literature. Our results support hybridization as one of the main diversification forces, from an allopolyploidy event at the origin of the clade to multiple hybridization events during the early radiation of the clade in the Oligocene in Asia. We also recovered a niche conservatism scenario for the early divergence of most of the AsPG lineages with all the early ancestors displaying similar climatic preferences for transitional conditions between tropical and subtropical climates. Subsequently, the Miocene was characterized by the colonization of several geographic areas that resulted in the highest diversification rates whenever the clade moved to tropical areas. Indeed, diversification models for one of these highly diversified lineages point to a climate-dependent diversification pattern. At a smaller geographical and evolutionary scale, we also detected that the interaction of climate and colonization events have shaped the speciation processes in Hedera. The colonization of new areas in Macaronesia has led to three different patterns in Hedera: high genetic and climatic differentiation in the early divergent H. canariensis (sister to the rest of western ivies), intermediate in H. azorica (sister to H. helix), and low in the recently-diverged H. maderensis (nested in H. iberica). Niche conservatism between H. maderensis and H. iberica is interpreted as a preadaptation given their functional trait similarities, which are not shared by species that occur under different climates. Lastly, we studied biochemical functional traits related to the response to environmental stressors (i.e., leaf phenolic content) in the three ivy species occurring in western continental Europe (H. helix, H. hibernica and H. iberica) and obtained different geographical patterns of phenolic content variation in response to different climatic stressors, which suggests that an interaction of phylogenetic constraints and phenotypic plasticity modulate the response of ivies to climatic conditions. In summary, this research indicated that 1) hybridization, genome doubling, and climatic niche conservatism were the main evolutionary forces during the early evolution of the AsPG, and 2) the new environments available after the colonization of new areas drove the diversification patterns later in the evolution of the AsPG genera. This research highlights the relevance of climate in the evolution of Araliaceae, which was overshadowed in previous studies by other patterns such as polyploidization and geographical processes, and highlights the importance of considering the interplay between biotic and abiotic patterns to understand plant diversification.
