Fig. 1.

Design of the pond experiment. (A) Entrance to the Little Campbell River from the Strait of Georgia, BC. (B) Cranby Lake, BC. (C) A single intercross (F0) was made between a marine (anadromous) stickleback collected in the Little Campbell River and a freshwater-resident stickleback from Cranby Lake. Example specimens are stained with alizarin red to highlight bone. The marine population is fully plated (MM genotype at the Eda locus), whereas the freshwater population has few lateral plates (FF at Eda). First generation (F1) hybrids were crossed in the laboratory to produce second-generation (F2) hybrids that were introduced to a freshwater pond at the University of British Columbia. (D) Author M.E.A. on the experimental pond. (E) Author K.B.M. returning adult F2 hybrids to the pond after measurement.