Predicting the Dispersal Potential of an Invasive Polychaete Pest along a Complex Coastal Biome

Area of Science:

• Marine Biology
• Invasive Species Ecology
• Population Genetics

Background:

• Boccardia proboscidea is an invasive polychaete worm causing significant damage to South Africa's abalone aquaculture industry.
• Concerns are rising as populations spread from farms into wild marine ecosystems, posing a threat due to its invasive nature globally.
• Understanding dispersal is crucial for managing this invasive species, especially in its early invasion stages.

Purpose of the Study:

• To assess the dispersal potential of Boccardia proboscidea in South Africa.
• To investigate the roles of natural oceanographic processes versus anthropogenic factors in the species' spread.
• To use population genetics and oceanographic modeling to understand connectivity and barriers.

Main Methods:

• Population genetic analysis of the invasive worm Boccardia proboscidea using mitochondrial (Cyt b) and nuclear (ATPSa) markers.
• Utilized Polydora hoplura, a similar pest species, as a proxy for dispersal studies due to B. proboscidea's incipient invasion stage.
• Employed a high-resolution Regional Ocean Modeling System (ROMS) with passive drifters to simulate larval dispersal along the southern African coast.

Main Results:

• Genetic data revealed low population structure (Φ = 0.04) and no clear geographic patterning of haplotypes, indicating high connectivity.
• Oceanographic modeling identified limited larval connectivity around Cape Point, a known marine biogeographic barrier.
• A significant discordance was observed between genetic connectivity and modeled oceanographic dispersal patterns.

Conclusions:

• Anthropogenic activities, such as aquaculture and shipping, are likely the primary drivers of B. proboscidea dispersal, overriding natural oceanographic barriers.
• The study suggests that cryptic (human-mediated) dispersal may lead to an overestimation of natural genetic connectivity.
• While natural barriers like Cape Point exist, human transport is critical for the widespread establishment of this invasive species along the South African coast.