Connectivity is fundamental to ecological and evolutionary processes in marine eco-
systems. Broadcast-spawning species are traditionally considered as excellent dispersers
due to their pelagic development. However, their dispersal potential might have been
overestimated and factors like oceanographic features and biological traits overlooked.
A more balanced view of connectivity is still needed, especially in the rapidly changing
Southern Ocean. This study used single nucleotide polymorphisms from RAD sequencing
to investigate connectivity and population structure of the broadcast-spawning Antarctic
sea urchin Sterechinus neumayeri along the Western Antarctic Peninsula. A hierarch-
ical sampling allowed multi-scale comparisons. Analysis of 877 SNPs suggests that S.
neumayeri forms a single, well-connected population at large spatial scales (>500km).
However, at intermediate (50-200km) and small scales (500m-5km), weak yet significant
genetic differentiation was detected. Small-scale genetic structuring aligns with larval
self-recruitment and collective dispersal reported in East Antarctica. Limited connectiv-
ity at intermediate levels is consistent with local oceanographic conditions, limiting gene
flow along the WAP. Large-scale genetic similarity may reflect historical recolonisation
post-glaciation or long-distance larval transport by the Antarctic Circumpolar Current.
In parallel, the study assessed whether MALDI-TOF MS protein profiling could provide
additional information on population structuring, but found little geographical signal in
the protein mass spectra.
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