Data from: Fine-scale genetic structure of small fish populations in islands: The case of brook charr Salvelinus fontinalis (Mitchill, 1814) in Saint-Pierre and Miquelon (France)

Island ecosystems, particularly vulnerable to environmental challenges,
host many endangered native species. Diadromous fish, in particular, are
threatened throughout their marine and freshwater habitats. The
conservation of these species requires an in-depth understanding of their
genetic diversity and structure, to better understand their adaptive
potential. We investigated fine-scale population diversity and structure
in native brook charr (Salvelinus fontinalis) by genotyping ten
microsatellite loci in 244 individuals at three spatial scales in
Saint-Pierre and Miquelon, France. We found limited genetic variability
across the archipelago, with particularly low genetic diversity in one
island, Langlade. A significant difference in allelic richness was also
detected among the three islands, indicating a difference in genetic
composition across the archipelago, probably induced by historical
stocking actions on both Saint-Pierre and Miquelon. Finally, a strong
genetic structure was detected across the archipelago among hydrosystems
(overall FST = 0.19) and even within several of them. The presence of
predominant inter-island gene flow combined with complete genetic
isolation from certain hydrosystems, suggests that this contemporary
genetic structure is the result of both natural demographic processes
during the species post-glacial colonization, and recent restocking
actions. The complex genetic structure of such isolated brook charr
subpopulations highlights the importance of considering fine-scale genetic
structure in conservation management.