Format: ORAL

Sreetama Bhadra1,2, Ilia J. Leitch3, Sidonie Bellot3, William J. Baker3, Renske E. Onstein4,1,2

1 German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, sDiv, Evolution and Adaptation, Puschstraße 4, Leipzig, 04103, Germany 2 Leipzig University, Ritterstraße 26, 04109 Leipzig, Germany 3 Royal Botanic Gardens, Kew, Kew Green, Richmond TW9 3AE, UK 4 Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands

Survival of plants in their environment depends on their ability to adapt and diversify. Genome size, due to its biophysical effects, may influence evolution of functional traits, and hence adaptation and diversification. However, this has never been tested in a quantitative macroevolutionary framework. Here we hypothesize that genome size evolution plays a fundamental role in influencing trait flexibility (i.e., evolvability of traits over macroevolutionary times), and hence diversification rates. We predict that larger genomes will lead to lower trait flexibility, while higher rates of genome size evolution will positively influence trait flexibility of plant lineages allowing for greater partitioning of ecological space, leading to speciation, and hence diversification. To address this hypothesis, we integrated genome size, functional trait, and phylogenetic data for palms (Arecaceae) - a pantropical plant family comprising ca. 2600 species that express wide functional diversity. Using macroevolutionary and structural equation models we show that diversification rates of palms increased c. 20 million years ago, concordant with increased rates of genome size and trait evolution. Furthermore, rate of genome size evolution was positively influenced by genome size itself, contrary to the idea that large genomes constrain evolution. Finally, we found that higher rate of genome size evolution was associated with greater trait flexibility (e.g., higher rates of fruit size, leaf size, and stem height evolution). Overall, our findings suggest that interactions between rates of genome size and trait flexibility have played a role leading to higher diversification rates in palms. Our results suggest that genome size evolution acts as a key driver of diversification in palms both directly, and indirectly via its influence on trait evolution. This may explain the complex interplay between genomic factors, traits and diversification leading to some of the most enigmatic evolutionary radiations across angiosperms and the ecological success of certain plant lineages.