Global change impacts on the Earth System are typically evaluated using biome classifications based on trees and forests. However, during the Cenozoic, many terrestrial biomes were transformed through the displacement of trees and shrubs by grasses. While grasses comprise 3% of vascular plant species, they are responsible for more than 25% of terrestrial photosynthesis. Critically, grass dominance alters ecosystem dynamics and function by introducing new ecological processes, especially surface fires and grazing.However, the large grassy component of many global biomes is often neglected in their descriptions, thereby ignoring these important ecosystem processes. Furthermore, the functional diversity of grasses in vegetation models is usually reduced to C3 and C4 photosynthetic plant functional types, omitting other relevant traits. Here, we compile available data to determine the global distribution of grassy vegetation and key traits related to grass dominance. Grassy biomes (where > 50% of the ground layer is covered by grasses) occupy almost every part of Earth's vegetated climate space, characterising over 40% of the land surface. Major evolutionary lineages of grasses have specialised in different environments, but species from only three grass lineages occupy 88% of the land area of grassy vegetation, segregating along gradients of temperature, rainfall and fire. The environment occupied by each lineage is associated with unique plant trait combinations, including C3 and C4 photosynthesis, maximum plant height, and adaptations to fire and aridity.

Summary Plant allometries help us to understand resource allocation in plants and provide insight into how communities are structured. For woody species, a triangular allometric relationship between seed size and leaf size occurs in which all combinations are all possible, except for species with big seeds and small leaves (Cornelissen ). This relationship is thought to be a consequence of between‐habitat variation in abiotic conditions. In this study, we tested if the triangular relationship between seed mass and leaf area holds for annual species, and if variation in soil productivity and light (measured as Ellenberg indicator values: EIVs) is driving this relationship. We show that the triangular relationship also holds for annuals, which suggests that the allometric combinations between leaf area and seed mass are conserved across life‐forms. The triangular relationship was driven by between habitat variation in soil productivity. This means that as soil productivity increases, plants with bigger leaves could have either big or small seeds. However, in low soil productivity habitats, plants are constrained in their options, and plants with small leaves can only have small seeds. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12870/suppinfo is available for this article.

Although key elements defining the juvenile growth phase remain unmeasured, our results broadly support SPL theory in that phytometer and leaf size are a product of the size of the initial shoot meristem (≅ seed mass) and the duration and quality of juvenile growth. These allometrically constrained traits combine to confer ecological specialization on individual species. Equally, they appear conservatively expressed within major taxa. Thus, 'evolutionary canalization' sensu Stebbins (Stebbins GL. 1974. Flowering plants: evolution above the species level . Cambridge, MA: Belknap Press) is perhaps associated with both seed and leaf development, and major taxa appear routinely specialized with respect to ecologically important size-related traits.

Priming in soil seed banks may be costly because of high predation, so seed protection during priming is sufficient to promote the evolution of serotiny. Bet hedging contributes to this process. Rapid germination of primed seeds that respond to brief rainfall events is disadvantageous because such rainfall is insufficient for seedling survival. Serotinous species counteract this cost by cueing dispersal with heavy precipitation.

Background and Aims Plants depend fundamentally on establishment from seed. However, protocols in trait-based ecology currently estimate seed size but not seed number. This can be rectified. For annuals, seed number should simply be a positive function of vegetative biomass and a negative one of seed size. Methods Using published values of comparative seed number as the ‘golden standard’ and a large functional database, comparative seed yield and number per plant and per m2 were predicted by multiple regression. Subsequently, ecological variation in each was explored for English and Spanish habitats, newly-calculated CSR strategies and changed abundance in the British flora. Key Results As predicted, comparative seed mass yield per plant was consistently a positive function of plant size and competitive ability and largely independent of seed size. Regressions estimating comparative seed number included, additionally, seed size as a negative function. Relationships differed numerically between regions, habitats and CSR strategies. Moreover, some species differed in life history over their geographical range. Practically, comparative seed yield per m 2 was positively correlated with FAO crop yield, and increasing British annuals produced numerous seeds. Nevertheless, predicted values must be viewed as comparative rather than absolute: they varied according to the ‘golden standard’ predictor used. Moreover, regressions estimating comparative seed yield m -2 achieved low precision. Conclusions For the first time, estimates of comparative seed yield and number for over 800 annuals and their predictor equations have been produced and the ecological importance of these regenerative traits has been illustrated. ‘Regenerative trait-based ecology’ remains in its infancy with work needed on determinate versus indeterminate flowering (‘bet-hedging’), C-S-R methodologies, phylogeny, comparative seed yield per m 2 and changing life-history. Nevertheless, this has been a positive start and readers are invited to use estimates for >800 annuals, in the Supplementary Data, to help advance ‘regenerative trait-based ecology’ to the next level.

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