A simple mechanistic model of the invasive species Heracleum sosnowskyi propagule dispersal by wind

Background. Invasive species are one of the key elements of human-mediated ecosystem degradation and ecosystem services impairment worldwide. Dispersal of propagules is the first stage of plant species spread and strongly influences the dynamics of biological invasion. Therefore, distance prediction for invasive species spread is critical for invasion management. Heracleum sosnowskyi is one of the most dangerous invasive species with wind-dispersed propagules (seeds) across Eastern Europe. This study developed a simple mechanistic model for H. sosnowskyi propagule dispersal and their distances with an accuracy comparable to that of empirical measurements. Methods. We measured and compared the propagule traits (terminal velocity, mass, area, and wing loading) and release height for H. sosnowskyi populations from two geographically distant regions of European Russia. We tested two simple mechanistic models: a ballistic model and a wind gradient model using identical artificial propagules. The artificial propagules were made of colored paper with a mass, area, wing loading, and terminal velocity close to those of natural H. sosnowskyi mericarps. Results. The wind gradient model produced the best results. The first calculations of maximum possible propagule transfer distance by wind using the model and data from weather stations showed that the role of wind as a vector of long-distance dispersal for invasive Heracleum species was strongly underestimated. The published dataset with H. sosnowskyi propagule traits and release heights allows for modeling of the propagules' dispersal distances by wind at any geographical point within their entire invasion range using data from the closest weather stations. The proposed simple model for the prediction of H. sosnowskyi propagule dispersal by wind may be included in planning processes for managing invasion of this species