Seasonal Divergence of <i>Bosmina</i> Morphs

Abstract

Abstract Seasonal occurrence and vertical distribution of two sympatric Bosmina morphs were investigated in two oligotrophic, deep fjord‐type lakes. Bosmina obtusirostris and B. lacustris displayed similar ecology, but B. obtusirostris exhibited more eggs per clutch. B. obtusirostris is probably the most viable of the two morphs when fish predation is relaxed, while B. lacustris exhibits an advantage with increasing fish and invertebrate predation. This has important consequences for habitat selection of the two morphs. B. obtusirostris and B. lacustris are most probably two phenotypes of a polymorphic species.