Within‐and among‐year germination in Sonoran Desert winter annuals: bet hedging and predictive germination in a variable environment

In variable environments, organisms must have strategies to ensure fitness as conditions change. For plants, germination can time emergence with favourable conditions for later growth and reproduction (predictive germination), spread the risk of unfavourable conditions (bet hedging) or both (integrated strategies). Here we explored the adaptive value of within- and among-year germination timing for 12 species of Sonoran Desert winter annual plants. We parameterised models with long-term demographic data to predict optimal germination fractions and compared them to observed germination. At both temporal scales we found that bet hedging is beneficial and that predicted optimal strategies corresponded well with observed germination. We also found substantial fitness benefits to varying germination timing, suggesting some degree of predictive germination in nature. However, predictive germination was imperfect, calling for some degree of bet hedging. Together, our results suggest that desert winter annuals have integrated strategies combining both predictive plasticity and bet hedging

Linking performance trait stability with species distribution: the case of Artemisia and its close relatives in northern China

Aims: Understanding the relationship between species and environments is at the heart of ecology and biology. Ranges of species depend strongly on environmental factors, but our limited understanding of relationships between range and trait stability of species across environments hampers our ability to predict their future ranges. Species that occur over a wide range (and thus have wide niche breadth) will have high variation in morpho-physiological traits in response to environmental conditions, thereby permitting stability of performance traits and enabling plants to survive in a range of environments. We hypothesized that species' niche breadth is negatively correlated with the rate of performance trait change along an environmental gradient. Location: Northern China. Methods: We analysed standing biomass and height of 48 species of Asteraceae (Artemisia and its close relatives) collected from 65 sites along an environmental gradient across northern China. Results: In support of our hypothesis, there were significant negative correlations between climatic niche breadth and rate of change in biomass, a performance trait, but not in height, which is both a morphological and a performance trait. Conclusions: These findings have implications for risk assessment of species under climate change and prediction of unknown distributions of species. They also offer a new avenue of research for species distribution models. We show that there were significant negative correlations between climatic niche breadth and rate of change in biomass, a performance trait, but not in height, which is both a morphological and performance trait. Our findings have implications for risk assessment of species under climate change and prediction of unknown distributions of species