The Asteraceae, or daisy family, is the most species-rich family of all flowering plants and is one of the dominant families represented in many threatened ecosystems such as the grasslands and the high-altitude mountains. The family is characterised by its peculiar inflorescence –the capitulum– which mimics a flower but is in fact composed of a multitude of tightly grouped florets. The capitulum is seen as a key innovation that has greatly contributed to the impressive evolutionary success of the family. It also participates in the family’s economic success, since many species are cultivated for their capitulum for agricultural (e.g. the sunflower, the artichoke) and horticultural (e.g. Chrysanthemum, Gerbera) purposes. However, to date, there is still no comprehensive understanding of how the capitulum originated and how its morphology and structure varies across the Asteraceae. This is mainly due to a lack of appropriate tools for describing such a complex and condensed structure, together with the practical and analytical challenges of compiling (i.e. the data collection itself) and analysing very large datasets. CAPITULA focuses on syncephalous Asteraceae, which represent a model system specifically targeted –and uniquely suited– for studying inflorescence complexity in Asteraceae. While most species have a simple capitulum, in a few species the inflorescence is more complex as it is formed by bringing together multiple capitula to form a secondary capitulum (=syncephalia). Syncephalous species constitute invaluable material for deciphering the genetic basis and evolutionary origin of the capitulum because their genomes have undergone the inflorescence shift toward capitulescence twice thus allowing the genetic signature of capitula formation to be recovered twice. Our approach, integrating the most recent experimental and theoretical developments in evo-devo and genomics fields, provides a unique opportunity to ask fundamental questions relating to coordinated trait evolution, and to increase our understanding of how genetic pathways have been altered or co-opted during the evolutionary diversification of flowers
The clustering of flowers into inflorescences is a major recurrent evolutionary trend associated with pollinator attraction that has played an important role in the diversification of angiosperms. Research on the origin and evolution of inflorescence diversity is of prime importance when considering that much of our food relies on seed and fruit crops. Indeed, inflorescence structure determines the number and arrangement of flowers and fruits, and is thus vital for reproductive fitness and constitutes a key character for plant domestication and crop production.
CAPITULA’s main objectives are to: 1–Explore the morphological landscape of Asteraceae inflorescences, and provide insights on the biological and evolutionary significance of capitulum diversification in Asteraceae, 2–Identify the origin and assembly of the genetic pathways subtending inflorescence transitions and 3–Investigate the genomic changes (e.g. polyploidization, genome size shifts, transposable element activity) associated with capitulum evolution.
