Hydro-dispersal: From plasticity and diversity of form to function in Marchantia splash-cups – HYDROPOP

Despite the importance of phenotypic plasticity in the adaptation of organisms to their environment, it is difficult to make the links between underlying developmental mechanisms and components of organism fitness. We identified an ideal process to tackle this issue, dispersal by organs known as splash-cups: raindrops bounce off these organs and entrain reproductive units at a distance from the parent plant or fungus. Indeed, splash-cups have evolved independently in several lineages, and are present in the genetic model Marchantia polymorpha and in most species of the same genus of non-vascular plants, including Marchantia globosa that grows over a broad range of environmental conditions in the island of la Réunion. We will test the hypothesis that phenotypic plasticity of splash-cup morphology in Marchantia enables optimal dispersal, possibly by adapting splash-cup size to raindrop size. To do so, we will combine approaches from developmental biology, fluid mechanics, atmospheric physics, systematics and evolution, and ecology. We will quantify phenotypic plasticity of splash-cups in the field and lab, identify environmental parameters that are sensed to regulate their morphology, and characterise corresponding molecular mechanisms. We will examine whether splash-cups enable optimal dispersal by investigating splash-cup morphology across the Marchantia genus, raindrop characteristics in specific environments of the island of la Réunion, and hydrodynamics of drop impact on a splash-cup. Given the importance of dispersal for the colonisation of habitats, our work will be relevant for the understanding of the distribution of splash-cup-making species in the context of climate change.