Tracking invasion histories in the sea: facing complex scenarios using multilocus data.

Area of Science:

• Marine biology
• Invasive species research
• Population genetics

Background:

• Biological invasions pose significant threats to marine ecosystems.
• Understanding invasion routes is crucial for effective management.
• Molecular tools offer new insights into invasion histories.

Purpose of the Study:

• To investigate the invasion routes and colonization histories of the marine invertebrate Microcosmus squamiger.
• To identify the ancestral origins and introduction pathways of M. squamiger populations worldwide.
• To elucidate the role of human-mediated transport in marine invasions.

Main Methods:

• Microsatellite loci and mitochondrial DNA sequence data analysis.
• Discriminant analysis of principal components (DAPC) and clustering methods.
• Approximate Bayesian Computation (ABC) modeling to infer population histories.

Main Results:

• Introduced M. squamiger populations originated from a single admixture event involving two Australian ancestral regions.
• Colonization involved sequential, non-independent introductions along coastlines of Africa, North America, and Europe.
• Invasion sequence aligns with historical records: Mediterranean/South Africa, then California, and the NE Atlantic.

Conclusions:

• Marine invasion histories are complex, often involving multiple ancestral sources and stepping-stone introductions.
• Human-mediated transport is a key driver for the spread and success of widespread marine non-indigenous species.
• Admixture processes facilitate the range expansion of invasive marine organisms.