"Masting modeling: evolution towards an early phenology to control seed consumers."Gastebois, SabrinaIn many species of perennial plants, the intensity of fruiting is extremely variable from one year to the next and synchronized at the population level. This reproductive strategy, known as 'masting', has major ecological and economic repercussions (notably the masting of oaks) and also represents an evolutionary enigma. Based on a theoretical approach, we test the hypothesis that the evolution of floral phenology could play a pivotal role in controlling masting. A relatively early phenology would often expose the trees to climatic contingencies (late frosts), leading to frequent reproductive failures and occasionally, great fruiting success. The resulting stochastic fruiting dynamics would be particularly effective in controlling a wide diversity of consumers, such as the insects that parasitise oak acorns. Trees could thus save a large proportion of their seeds from insect infestation. To assess the relevance of this hypothesis, an individual-based and stochastic eco-evolutionary model was developed, coupling a forest regeneration model with models of tree reproduction dynamics, floral phenology and insect community dynamics. In these models, individuals with different phenological strategies are introduced and compete for space (replacing dead adult trees) through recruitment from insect-free seeds. Using the adaptive dynamics framework, we show that insect selection pressure can make the phenology evolve towards greater precocity, generating stochastic fruiting dynamics and thus efficiently controlling insect populations. Our research demonstrates that early phenology, despite frequent reproductive failures, can provide a selective advantage, contrary to conventional intuition. As phenology is very sensitive to climate change, we can expect major changes in the masting of oak trees, with far-reaching repercussions on the dynamics of the associated ecosystems. |
« back