Fig. 3

Temporal pattern of directional selection (β′) on the spine length of the columnar cactus Echinopsis chilensis (N = 2,541) and Eulychnia acida (N = 459) during ten consecutive years at Las Chinchillas National Reserve. Cactus height and number of columns were considered as covariate in multivariate selection analyses (Lande and Arnold 1983; Brodie et al. 1995). Fruit production per cactus was considered as female fitness. Bars to the right of zero indicate selection in that year for plants with longer spines and bars to the left of zero indicate selection in that year for shorter spines. Asterisks indicate values significantly larger or smaller than zero. *P < 0.05, **P < 0.01, ***P < 0.001