Unusual number of pectoral fin rays in an Icelandic population of threespine stickleback (Gasterosteus aculeatus) recently isolated in freshwater

摘要

Threespine stickleback most often have 10 pectoral fin rays, and it seems to be a highly canalized trait. We observed an unusually high frequency of stickleback with 11 pectoral fin rays in a population recently isolated from the marine environment ina freshwater lagoon in Iceland. These new morphologies may be beneficial for the fish in the new habitat but may disappear because of strong canalizing selection for the typical 10 pectoral fin rays.