Functional convergence among pelagic sculpins of Lake Baikal and deepwaterciscoes of the Great Lakes

The vast, well-oxygenated hypolimnia of Lake Baikal and the Great Lakes wer e both dominated by endemic planktivorous fishes. These dominants, two spec ies of sculpins (Comephorus, Comephoridae) in Lake Baikal and sh species of deepwater ciscoes (Coregonus, Salmonidae) in the Great Lakes, although dis tant taxonomically, have morphologies suggesting a surprising degree of fun ctional convergence. Here it is proposed that the same two buoyancy-regulat ion strategies observed in Baikal sculpins also arose in the deepwater cisc oes of the Great Lakes. One strategy favors hydrostatic lift (generated by low specific gravity) and is characterized by fatter, larger-bodied fish wi th smaller paired fins; the second strategy favors hydrodynamic lift (gener ated by swimming) and is characterized by leaner smaller-bodied fish with l arger paired fins. Both types likely evolved to feed on a single species of ecologically analogous, vertically migrating macrozooplankter: Macrohectop us branickii in Lake Baikal and Mysis relicta in the Great Lakes. It is sug gested that Coregonus did not diversify and proliferate in Lake Baikal as t hey did in the Great Lakes because by the time Coregonus colonized Lake Bai kal, pelagic sculpins were already dominant.