Tulipa: the taxonomy and evolutionary history of the genus and its impact on conservation priorities in Central Asia

Tulips are one of the most recognisable plants with their current horticultural trade estimated as a billion-euro industry. This trade initially relied heavily on wild specimens but now relies less on natural diversity. Yet, wild tulips are an important genetic reserve for future breeding efforts, especially for disease resistance. They also have significant cultural value, can act as ecological indicators, and support insect populations. Their taxonomy is notoriously complex, complicating their study and conservation. Most taxa grow in Central Asia, which has been proposed as the place of origin of this genus, albeit with limited evidence. Many tulips are declining in this area, but there is no cohesive regional overview of the genus. Here, we address phylogeny and taxonomy within the genus, then using this insight to explore the evolutionary history of Tulipa and its potential to inform conservation priorities in Central Asia. First, we used modern phylogenetic techniques, with extensive sampling of the genus including large amounts of wild material collected during three fieldwork seasons, to generate both a plastome based and 35S rDNA phylogeny. These phylogenies allowed us to make a number of taxonomic decisions with respect to the synonymization and reinstatement of a number of species. We also reorganised the higher-level taxonomic groups of this genus recognising a new subgenus, Eduardoregelia, and simplifying the sections of this genus, primarily merging Tulipa, Tulipanum, Lanatae, Vinistriatae, and Spiranthera into one broader section. Within this work we identified a new species, Tulipa toktogulica, which we formally describe within this thesis as well. Second, we used molecular dating techniques to estimate the ages of nodes on the tulip species phylogeny. With this dated phylogeny we modelled the biogeographical history of the genus, generated a lineage through time plot, and assessed the phylogenetic signal for the trait of genome size, which has commonly been used in the taxonomy of tulips including in the description of new species. We then assimilated dates, biogeography, and geological history to propose how this genus diversified and migrated to its current distribution. We confirmed a broader Central Asian origin of this genus, highlighting the importance of this region for the diversification of this genus throughout its evolutionary history, and linking speciation to aridification, mountain building, and global cooling. Finally, we modelled the impacts of climate change on tulip species in Central Asia showing the large negative impact this threat will have. This information was then used in the Red Listing of a range of Central Asian tulip species, which was undertaken at a workshop in Bishkek in Spring 2022. Through this process, a large amount of information was collated and many taxa from this region were assigned a threat status. Using data from the Red List assessments we undertook several post-analyses, showing that national assessments often overinflate threat status, as well as calculating EDGE scores in order to stimulate evolutionarily informed conservation efforts. Overall, we have provided a foundation for the development of a regional tulip conservation strategy and improved conservation prioritisation, both of which directly support the work of our iCASE partner Fauna & Flora International.

Natural Environment Research Council DTP iCASE (Fauna & Flora International)