Informing spread predictions of two alien snails using movement traits

Area of Science:

• Ecology
• Invasive Species Biology
• Animal Behavior

Background:

• Aquatic ecosystems are vulnerable to invasive alien species, which disrupt ecological functions, reduce biodiversity, and cause economic damage.
• Understanding the dispersal mechanisms of invasive species is crucial for predicting their spread and managing their impact.
• Locomotion and exploratory behavior are key factors influencing the rate at which alien species colonize new environments.

Purpose of the Study:

• To quantify in-field densities of two invasive alien snails, Tarebia granifera and Physa acuta.
• To compare the movement traits, including dispersal potential and exploratory behavior, of T. granifera and P. acuta.
• To assess the role of animal behavior in the spread of invasive aquatic snails.

Main Methods:

• In-field densities of T. granifera and P. acuta were measured.
• Movement traits were quantified, including net distance, velocity, turning angles (absolute and relative), and straightness index.
• Dispersal potential was assessed by net distance and velocity.
• Exploratory behavior was proxied by turning angles and straightness index.

Main Results:

• Tarebia granifera exhibited significantly higher velocity and covered greater net distances compared to Physa acuta, indicating a higher dispersal rate.
• In-field densities were high for both species (T. granifera: 351 individuals m⁻²; P. acuta: 235 individuals m⁻²), with spatial variations.
• No significant differences in exploratory behavior (turning angles, straightness index) were observed between the two species; both showed a slight counterclockwise turning tendency.

Conclusions:

• Tarebia granifera possesses a greater capacity for self-dispersion than Physa acuta, potentially facilitating faster spread in aquatic systems.
• Animal behavior, particularly individual movement capacity, plays a significant role in promoting biological invasions.
• Autecological information on invasive species behavior is vital for developing accurate predictive models for freshwater ecosystem management.