Sample plots (50 x 50 m) illustrating the location of each tree of diameter at breast height (DBH) above 7 cm in the very rare and species-rich *Picea chihuahuana* tree community in Quebrada de los Durán (QD) and San José de las Causas (SJ), Durango (Mexico). S1 represents the *P*. *chihuahuana* trees (above), and S2–S7 represent the other tree species. For the point patterns in the QDand SJ plots, univariate *L*-functions are represented by black lines. The 99% simulation envelope (dashed red lines) for the CSR hypothesis was calculated via the Monte Carlo Method (Besag 1977), with 1,000 simulations (central). For the point pattern in the QD and SJ plots, the bivariate L-function is indicated represented by black lines. The 99% simulation envelope (dashed red lines) for the Independence hypothesis was calculated by the Random Shifting Method (Lotwick & Silverman, 1983), with 1,000 simulations (below).