Interactions Between Sediment Nutrient Contents and Propagule Pressure Affect the Establishment Success of a Nonnative Aquatic Plant (<i>Hydrilla verticillata</i>)

ABSTRACT The process of species invasion involves multiple factors, with resources and propagule pressure being key contributors. However, determining the relative importance of these factors in the establishment of nonnative aquatic plants, such as Hydrilla verticillata , remains unclear. This study aimed to test the hypothesis that resource availability, that is, sediment nutrient contents, is more pivotal than propagule pressure for the sinking and subsequent establishment of H. verticillata . We conducted an experiment using 64 tanks (60 × 30 × 40 cm) with two resource levels (low and high sediment nutrient contents), eight propagule pressure levels, and varying submersion times for establishment. Both sediment nutrient level and time submersion significantly affected propagule establishment. The interaction between sediment nutrient level and propagule pressure proved fundamental for the establishment of H. verticillata propagules. The high‐nutrient treatment showed more rooted propagules than the low‐nutrient treatment, especially under high propagule pressure. However, the low‐nutrient treatment also showed increased numbers of rooted propagules at higher propagule pressure. This implies that environments with low sediment nutrient concentrations can still support invader establishment, where propagule pressure may compensate for nutrient deficiency.