Effects of rainfall seasonality and seed size on seed dormancy in a perennial tropical plant

Abstract

In seasonal environments, precise timing of germination to match favorable environmental conditions is crucial for successful plant establishment. The timing of germination can be controlled by seed dormancy, i.e. delay in germination of viable seeds during some period of favorable conditions. Germination behavior can further depend on seed size, and larger seeds are usually predicted to be less dependent on dormancy than are smaller ones. In the tropics, information about dormancy is scarce in the literature. I studied the germination behavior of four populations of Dalechampia scandens from environments of contrasting rainfall seasonality in a common garden experiment. Seeds produced from the second greenhouse generation were measured and exposed to a favorable wet environment at different time intervals after dispersal. All populations produced a fraction of dormant seeds, and populations from less seasonal environments exhibited less seed dormancy compared to populations from more seasonal environments. Seed size had a negative effect on germination success. Overall, the study suggested that the level of dormancy is adapted to local environmental conditions. Variation in germination behavior among populations is important and it helps to understand local adaptation and for instance how species might respond to changes in the climate.