干旱区生态环境知识资源中心

1. Dormancy and dispersal are thought to be major adaptive mechanisms that enable short-lived organisms to cope with environmental stochasticity. The few empirical investigations that have explored the relationship between these two strategies in disturbed environments have focused mainly on communities of annual desert plants and suggest that dispersal plays a negligible role, as compared with dormancy, in reducing the risk of genotype extinction.

2. We predict that the relative advantage of dormancy versus dispersal is likely to be more balanced in species that disperse actively to select their reproductive locality.

3. To examine this prediction, we explored the dormancy and dispersal capacities of four actively dispersing sibling weevil species (Curculio spp.) that exploit the same, highly variable resource (oak acorns). The ability of each species to spread risks over time was estimated from the variability of dormancy duration within cohorts, while their ability to disperse spatially was quantified by flight performance.

4. We show that a first species, C. elephas, which was able to spread risk over time through dormancy, exhibited only medium flight capacities. In contrast, a second species, C. glandium, was able to fly over very long distances, but was hardly capable of spreading risk over time. Surprisingly, the two remaining species (C. venosus and C. pellitus) proved inefficient in spreading risk either in space or in time and seem to exhibit risk avoidance rather than risk-spreading strategy. We conclude that this strong diversification of dispersal-dormancy strategies observed among these four sibling species might contribute to stabilising their coexistence.