In 1-quart saucepan, mix 1 cup of the blueberries, the lemon peel, lemon juice, tapioca and 2 tablespoons sugar. Using potato masher or fork, mash blueberry mixture well. Cook over medium-low heat about 15 minutes, stirring constantly, until thickened. Stir in remaining 2 cups blueberries. Spread lemon pie filling evenly over top of cooled pie. Pour blueberry mixture on top. Refrigerate until ready to serve. Garnish with lemon slices and pecan halves. Cover and refrigerate any remaining pie.