Many ways to play dead: diversification in form and function among the world's largest flowers.

The Rafflesia genus, known for producing the largest flowers on Earth, contains 40 species that possess a remarkable diversity in flower size and shape. Rafflesia is also known as the corpse flower because of its foul smell: it attracts flies as pollinators by mimicking corpses. To examine how these flowers emit scents to attract and deceive pollinators, we combine models from fluid dynamics and stochastic processes. In particular, we simulate the trajectories of flies, a stochastic motion biased by the strength and gradient of the concentration of chemical emitted by the flower, focusing on how size and morphology impact scent diffusion and likelihood of pollination. We infer that flower geometry and dimensions have a profound influence on pollinator behavior, suggesting morphological divergence may have evolved in response to different local pollinator species assemblages. This may have been a significant evolutionary force in the divergence of Rafflesia across the southeast Asian archipelago. Our exploration provides insights into the connection between flower size, flower shape, scent dispersion, and pollinator attraction, and offers a mathematical perspective on the evolutionary pressures driving gigantism in the world’s largest flowers.