Our latest paper examining the role of life history traits in explaining the vast unevenness of species diversity across the flowering plant Tree of Life has just appeared online at PLoS Biology. The paper was led by Javi Igea and emerged from a very successful BBSRC DTP rotation project by Eleanor Miller, in collaboration with Alex Papadopulos.
Using the largest available phylogenetic tree of plants coupled with an unparalleled trait dataset, we analysed how seed size and its rate of change across the phylogeny were correlated with the rate of species formation. Seed size is crucial to plant evolution because it confers adaptation to different environment conditions and influences many other aspects of life history, including dispersal, resistance to stress, and colonisation potential. We subsequently found that faster rates of seed size change were associated with faster rates of speciation, probably by fostering the appearance of reproductive barriers between lineages. We also found that smaller-seeded species speciated faster than larger-seeded ones. These results underscore the importance of morphological traits, and particularly their rate of evolution, in promoting species divergence across one of the largest radiations of organisms on the planet.
Although it has taken a bit longer than we would have liked – no thanks to some poor timing with #BAMMgate – the paper brings together an impressive toolbox of complementary macro-evolutionary analyses to deliver a compelling explanation for one of nature’s enduring mysteries. Well done all!