On the Ecology and Evolution of seed and Bud Dormancy

Sammanfattning: This thesis considers the ecological and evolutionary significance of seed and bud dormancy. First, I present theoretical support to the idea that seed dormancy may evolve as a strategy to reduce sib competition in temporally homogeneous environments. In this thesis, I also analyze two different processes that may give rise to parent-offspring conflicts in angiosperms, viz. seed germination and seed provisioning. In either case, I use a single fitness function for a single individual, whereas in earlier contributions fitness for parents and offspring are given distinct definitions. I show that there exists an ESS, and that this ESS is best seen as a compromise between conflicting selection pressures acting upon genes with age-specific expression rather than as a conflcit between parents and offspring. Second, I outline a theoretical framework for the evolution of bud dormancy as an adaptation to a predictable risk of being damaged. The presence of dormant buds/latent meristems enables plants to compensate their meristem losses following damage by the regrowth of secondary and tertiary shoots. I show that intensive and predictable herbivory may select for compensatory growth in plants. An interesting result of the present thesis is that the shape of compensatory responses in relation to meristem loss differs between qualitatively between plants adapted to single grazing episode and plants adapted to repeated grazing events. Finally, I present empirical evidence for an evolutionary history of overcompensation in the herb Gentianella campestris (Gentianaceae). BY overcompensation, I undestand the fact that damaged plants produce more fruits and seeds than do undamaged plants.