Microsatellite data of Southern Dunlin breeding across the Baltic

The stored data were used in a study by Rönkä et al. (2021). See full
citation in Usage notes. Here is the abstract of Rönkä et al. (2021).
Background: Populations living in fragmented habitats may suffer from loss
of genetic variation and reduced between-patch dispersal, which are
processes that can result in genetic differentiation. This occurs
frequently in species with reduced mobility, whereas genetic
differentiation is less common among mobile species such as migratory
birds. The high dispersal capacity in the latter species usually allows
for gene flow even in fragmented landscapes. However, strongly philopatric
behaviour can reinforce relative isolation and the degree of genetic
differentiation. The Southern Dunlin (Calidris alpina schinzii) is a
philopatric, long-distance migratory shorebird and shows reduced dispersal
between isolated breeding patches. The endangered population of the
Southern Dunlin breeding at the Baltic Sea has suffered from habitat
deterioration and fragmentation of coastal meadows. We sampled DNA across
the entire population and used 12 polymorphic microsatellite loci to
examine whether the environmental changes have resulted in genetic
structuring and loss of variation. Results: We found a pattern of
isolation-by-distance across the whole Baltic population and genetic
differentiation between local populations, even within the southern
Baltic. Observed heterozygosity was lower than expected throughout the
range and internal relatedness values were positive indicating inbreeding.
Conclusions: Our results provide long-term, empirical evidence for the
theoretically expected links between habitat fragmentation, population
subdivision, and gene flow. They also demonstrate a rare case of genetic
differentiation between populations of a long-distance migratory species.
The Baltic Southern Dunlin differs from many related shorebird species
that show near panmixia, reflecting its philopatric life history and the
reduced connectivity of its breeding patches. The results have important
implications as they suggest that reduced connectivity of breeding
habitats can threaten even long-distance migrants if they show strong
philopatry during breeding. The Baltic Southern Dunlin warrants urgent
conservation efforts that increase functional connectivity and gene flow
between breeding areas.