Fig. 2From: Arms Race Coevolution: The Local and Geographical Structure of a Host–Parasite InteractionEffect of spine length as a barrier to infection in Echinopsis chilensis and Eulychnia acida. Columns indicate mean (SE). Degrees of freedom are: E. chilensis = 1,217 and E. acida = 1,66. **P < 0.01, ***P < 0.001. See details in Medel 2000Back to article page