Appendix B. A figure showing the effect of laboratory diet on snail drilling capacity.
|FIG. B1. Test of whether the common laboratory diet used to raise F2 snails (Nucella canaliculata) influenced the frequency of predation on the mussel Mytilus californianus. One family lineage was tested from each of four populations (BH, VD, SH, FC; see Fig. 1 for site information). At hatching, 200 F2 snails from each lineage were divided equally into two mesh-sided strainers and were raised exclusively on a diet of either the blue mussel M. trossulus (as in all other experiments), or an alternative diet of acorn barnacles (small Balanus glandula and Chthamalus dalli attached to pieces of mussel shell). Once snails had reached adult size (18–25 mm long, 12 months later), all snails were randomly assigned to independent 1-L containers and were provided 50–70 mm long M. californianus. For each of the four family lineages, bars show the percent of snails drilling at least one M. californianus during a 100-d trial (black bars = M. trossulus-raised snails; gray bars = barnacle-raised snails). "0" indicates a group where no snails drilled mussels. Regardless of the diet that snails were raised on, family lineages from California (BH, VD) showed a high percent of successful predation on M. californianus relative to snails from Oregon populations (SH, FC). Number of snails tested in each group varied based on how many had survived to adult size (mean n = 11 snails per bar; range = 6–16).|