PARENT SESSION
Poster Session 35: Evolutionary Ecology
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Joint evolution of seed dispersal and dormancy to avoid kin competition.

Kobayashi, Yutaka^*,1, ¹ Center for Ecological Research, Kyoto University, Otsu, Shiga, JAPAN

ABSTRACT- The range of seed dispersal is more or less limited in plants. This may lead to competitive interaction between genetically related individuals, e.g., siblings. Since competition among relatives potentially decreases inclusive fitness of plants, plants are expected to evolve some strategies to reduce the competition. One effective strategy would be simply to increase dispersal efficiency. A series of theories tells that organisms can evolve to disperse themselves or their offspring even with quite high costs. Another way of avoiding kin competition would be seed dormancy. Although a few, there are also theoretical studies about this topic, and they showed that dormancy can evolve for reducing competition among kin even with costs of death due to, for example, predation or decay during dormancy. So far, these two series of theoretical studies, i.e., those of dispersal and dormancy, have independently developed. In this theoretical study, I construct a model of patchy structured population and investigate simultaneous (or joint) evolution of seed dispersal and dormancy. Using an inclusive fitness method, I calculate an evolutionarily stable set of dispersal and dormancy rates. The analysis shows that the cost of dispersal affects even the evolution of the dormancy rate through the evolution of the dispersal rate and the change in the relatedness between patch-mates (the evolutionarily stable dormancy rate increases with the dispersal cost). Likewise, the cost of dormancy affects the evolution of dispersal (the evolutionarily stable dispersal rate increases with the dormancy cost). Furthermore, I show that joint evolution sometimes yields interesting results, which are never obtained when we only consider individual evolution. For example, when we change the values of certain parameters, we see an abrupt and discontinuous change in the values of the evolutionarily stable dispersal and dormancy rates. This is caused by a kind of bifurcation (appearance and disappearance of stable points). The result of this study suggests the importance of considering joint evolution of multiple traits.

Key words: seed dispersal, seed dormancy, kin competition, inclusive fitness