Hidden responses to environmental variation: maternal effects reveal species niche dimensions.

Species responses to fluctuating environments structure population and community dynamics in variable ecosystems. Although offspring number is commonly used to measure these responses, maternal effects on offspring quality may be an important but largely unrecognised determinant of long-term population growth. We selected 29 species across a Mediterranean annual plant phylogeny, and grew populations of each species in wet and dry conditions to determine responses in seed number and maternal effects (seed size, seed dormancy, and seedling growth). Maternal effects were evident in over 40% of species, but only 24% responded through seed number. Despite a strong trade-off between seed size and seed number among species, there was no consistent trade-off within species; we observed correlations that ranged from positive to negative. Overall, species in this plant guild show a complex range of responses to environmental variation that may be underestimated when only seed number responses are considered.