Data from: Rare long-distance dispersal of a marine angiosperm across the Pacific Ocean

Aim: Long-distance dispersal (LDD) events occur rarely but play a
fundamental role in shaping species biogeography. Lying at the heart of
island biogeography theory, LDD relies on unusual events to facilitate
colonisation of new habitats and range expansion. Despite the importance
of LDD, it is inherently difficult to quantify due to the rarity of such
events. We estimate the probability of LDD of the seagrass Heterozostera
nigricaulis, a common Australian species, across the Pacific Ocean to
colonise South America.Location: Coastal Chile, Australia and the Pacific
Ocean. Methods: Genetic analysis of H. nigricaulis collected from Chile
and Australia were used to assess the relationship between the populations
and levels of clonality. Ocean surface current models were used to predict
the probability of propagules dispersing from South East Australia to
Central Chile and shipping data used to determine the likelihood of
anthropogenic dispersal. Results: Our study infers that the seagrass H.
nigricaulis dispersed from Australia across the entire width of the
Pacific (~14,000 km) to colonise South America on two occasions. Genetic
analyses reveal that these events led to two large isolated clones, one of
which covers a combined area of 3.47 km2. Oceanographic models estimate
the arrival probability of a dispersal propagule within 3 years to be at
most 0.00264%. Early shipping provides a potential alternative dispersal
vector, yet few ships sailed from SE Australia to Chile prior to the first
recording of H. nigricaulis and the lack of more recent and ongoing
introductions demonstrate the rarity of such dispersal. Main Conclusion:
These findings demonstrate LDD does occur over extreme distance despite
very low probabilities. The large number of propagules (100s of millions)
produced over 100s of years suggests that the arrival of propagules in
Chile was inevitable and confirms the importance of LDD for species
distributions and community ecology.