Abstract: The western US is predicted to be drier and experience more variable precipitation in the coming decades. Plants that survive in habitats with limited water do so by having certain combinations of functional traits (i.e. characteristics affecting performance) which allow them to either escape, avoid, or tolerate drought. In response to a changed environment, plant individuals, and plant populations may evolve favorable functional traits (heritable, genetic changes), pass on favorable traits from parent to offspring via epigenetics (heritable, non-genetic changes), or individually change their trait expression to suit the environment (phenotypic plasticity, non-heritable changes). Populations have been seen evolving over relatively short time-scales (rapid evolution) including in response to changed rainfall conditions. However, much of our knowledge on rapid evolution to changed rainfall conditions is confined to individual species and does not begin to tease out which species or types of species can evolve quickly and if certain traits or groups of traits are evolved by groups of species. We examined if, and how, thirteen short-lived California grassland species displayed adaptive changes after six years of altered water conditions. Our species differ in growth form, native status, lifespan, mating system, bloom time, and soil habitat. We are growing these individuals from the different water treatments in a common garden for two years and collecting trait measurements. Here I present data on seed weight and emergence; a subset of the data from this continued experiment. We found that seeds from low water treatments in the field tended to have higher seed mass while plants from high water treatments grown in the common garden tended to have higher seed mass. Higher seed mass correlates with lower seedling mortality during drought in this system. Our work may assist restoration practitioners in choosing seed of native plants that have the best chance of success. Our work will clarify how functional traits related to water availability vary within and between groups of short-lived grassland species. It will also help us better predict species ranges and survival in a changed climate.
