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Banded individuals of Littorina fabalis and Littorina saxatilis and their frequency across years. (a) Examples of L. fabalis individuals and sample frequency over a period of 7 years in the Spanish population of Abelleira; photographs by Dr. Daniel Estévez. (b) Examples of Littorina saxatilis individuals and average frequency over a period of 21 years for Swedish populations recolonized with banded (blue) or white and/or red (red) individuals; photographs by Fredrik Pleijel
