The colonization of land was a major milestone in Earth’s history, reshaping the course of evolution. Mosses were the first plants to inhabit the previously barren continents followed by the first animals, small arthropods. These pioneers established the foundation for modern terrestrial ecosystems and the diversity of life by dramatically re-shaping the global environment. Importantly, these organisms closely interacted through arthropods facilitating moss fertilization and the resulting spread of life across land.
As a relic of their aquatic origin, sexual reproduction in mosses depends on sperm released from the male organ swimming through water across a constrained distance to reach the egg in the female organ. After the transition to land, springtails (small non-insect arthropods) facilitated moss fertilization by transporting sperm to the female organs, significantly enhancing fertilization rates and dispersal. However, the molecular signaling pathways underlying moss reproduction, including the molecular cues that elicit sperm attraction and the sensory receptors by which sperm recognize conspecific eggs, remain unknown. Likewise, the mechanisms driving springtail behavior remain unexplored, including how these animals detect and respond to moss reproductive cues, and how mosses actively signal to recruit them. Understanding these interactions will shed light on the earliest example of animal-mediated fertilization on land, long before pollen-bearing plants came onto the scene.
Here, I propose to use molecular, electrophysiological, and behavioral approaches to explore how sensory receptors mediate interspecies communication and reproductive behavior, as a window into the process that drive evolution and speciation. I aim to identify the chemical cues mediating moss fertilization (Aim 1), characterize sperm receptors for species-specific fertilization (Aim 2), and explore how these signals were co-opted to attract springtails and shape dispersal and evolution on land (Aim 3). Organisms exist in dense, interconnected communities across all kingdoms of life. Studying how these interactions function and evolve will reveal insights with broad relevance for biology and disease.