The global biogeography of angiosperm genome size is shaped by climate and range size

Evolution of genome size is shaped by various intrinsic and extrinsic factors. We explored three long-standing hypotheses concerning factors shaping the global distribution of genome size: the mutational hazard hypothesis, the polyploidy-mediated hypothesis and the climate-mediated hypothesis. We compiled the largest genome size dataset to date, encompassing >5% of known angiosperm species and analysed genome size distribution using a comprehensive geographic distribution dataset for all angiosperms across all continents. Angiosperm species with large range sizes only have small genomes, consistent with the mutational hazard hypothesis. We also uncovered a unique latitudinal pattern in the distribution of genome size diversity. Climate had a strong effect on the latitudinal pattern in genome size, while the effect of polyploidy was small. Contrary to the unimodal latitudinal patterns found for plant size traits and polyploidy, the increase in angiosperm genome sizes from the equator to 40-50°N/S is probably mediated by different (mostly climatic) mechanisms from those underpinning the decrease in genome sizes observed from 40–50°N northwards. Overall, our global analyses highlight that species range size and climate factors are the main drivers shaping the global distribution of angiosperm genome sizes, with their relative importance varying across the latitudinal gradient.