Abstract/Summary

Changes in climatic conditions are important drivers of plant speciation initiating diversification, speciation, and extinction. The disruption of climate in recent decades that comes under the umbrella of climate change is affecting the current relationships between current plant distributions and climates, which is introducing new threats to biodiversity at a level not previously seen during human civilization. Narcissus has a centre of diversity in the Iberian Peninsula, a region with a complex climatic and geological history. Previous estimates of Narcissus divergence in the Miocene differ by 7.6 million years. Using next-generation sequencing, plastome (163 whole plastomes and a subset of 78 protein-coding genes from this) and low-copy nuclear (261 Angiosperms353 genes for 101 taxa), phylogenetic trees and networks were built to decipher the impact of past changes in climate on Narcissus diversification and distributional patterns, including the role of hybridisation across the genus. The dated plastome phylogeny of Amaryllidaceae indicated the Eurasian clade diverged 18.26 MYA (95% 12.22 – 24.75 MYA) and the Narcissus phylogeny indicated it diverged 13.64 MYA (95% HPD = 9.00 – 18.50 MYA) during the Miocene in the Iberian Peninsula. Climatic and geological events may have initiated allopatric and hybrid speciation across the genus and determined current distributions. High levels of cytonuclear discordance between plastome and nuclear phylogenies were recovered, which was attributed to hybridisation and introgression. Explicit phylogenetic networks confirmed the ancient hybrid origin of sections such as Dubii and Nevadensis, which occurred following climate-induced range shifts. Ancient hybridisation detected here, also explains discrepancies between morphological and molecular taxonomic treatments such as section Bulbocodii. The evolutionary relationships recovered by these phylogenetic analyses will contribute towards a taxonomic revision of Narcissus. Overall, this thesis demonstrates the significant role of climatic changes on Narcissus evolution, which initiated climate-induced diversification and speciation, with repeated range shifts initiating hybrid speciation.