Sympatric anadromous-resident pairs of threespine stickleback species in young lakes and streams at bering glacier, alaska

Resident freshwater and anadromous pairs of threespinc stickleback species (Gastews- leus (witteahts species complex) have been reported from only a few lakes. We discovered such pairs in four kikes and four streams, including recently deglaciated terrain, near the Bering Glacier. Alaska. Bering Glacier surges are accompanied and ended by massive glacial outburst floods, which create unmatched dynamics in the surrounding lakes and streams. This is the first report of a stickleback species pair in a proglacial lake (Vitus). which did not exist 100 years ago. These species pairs may have arisen through sympatrie speeiaiion from an anadromous ancestor, double invasion of anadromous stickleback, or independent colonization by resident and anadramous forms.