Beyond the Grant–Stebbins model: floral adaptive landscapes and plant speciation

Abstract

The Grant-Stebbins model, while inspiring decades of empirical studies, is a caricature of pollinator-driven speciation and explains only a limited range of adaptive outcomes. By using adaptive landscapes, we acknowledge that flowers are not adaptations to the most effective pollinator, but adaptations to maximize fitness, making evolutionary shifts between distinct floral phenotypes easier to understand in multi-pollinator environments. Finally, we argue that while pollinators often drive floral divergence, speciation most likely results from simultaneous divergence in multiple niche axes across a geographic range, which has been underemphasized in plant speciation research.