干旱区生态环境知识资源中心

AimEnvironmentally cued germination and seed banking are strategies employed by annual plants to persist in unpredictable climates. Moreover, such strategies may be key to persistence under more extreme and variable future climates. In regions with a mediterranean climate, cold-cued germination can allow populations to avoid germinating under unfavourable conditions and seed banks can buffer population growth in the face of inter-annual climate variability. Using widespread native annual plant species in the California Floristic Province (CFP), we ask: (1) How common are cold-cued germination and persistent seed banks? (2) Does the prevalence of cold-cued germination and seed bank maintenance shift predictably with climate? (3) Are germination strategies taxonomically linked?

LocationCalifornia, USA.

MethodsWe assessed seed bank persistence and temperature-cued germination in c. 175 populations of 42 species (eight families) from across California in the 2006 growing season. We then tested for evidence that the prevalence of these adaptations correlated with latitude, increasing climate variability and taxonomy.

ResultsOnly 19% of populations had significantly cold-cued seed germination and only 52% of populations had detectable seed banks. There were no significant relationships between the prevalence of cold-cued germination and any climate factor. Seed banking was significantly more common in regions with warm, dry conditions in the preceding year, but was not related to long-term climate averages. Variance in temperature-cued germination was best explained at the species level, with no variance explained by family.

Main conclusionsOur results suggest that germination of annual plants in the CFP is dominated by general risk aversion strategies rather than locally adaptive strategies linked to long-term climate factors. High germination variability within and among populations, coupled with increased seed banking under less favourable conditions, suggests that germination strategies are unlikely to limit this flora’s persistence under an increasingly harsh and unpredictable climate.