Evaluation of the conservation status of a rare cactus (Mammillaria crucigera) through the analysis of its population dynamics

We used population projection matrices to analyse the demography of Mammillaria crucigera, a rare cactus endemic to a small region in Central Mexico. Matrices were based on a 2-year period of observations on survival, growth and reproduction. No seed germination or seedling survival were observed; thus, these matrix entries were experimentally estimated. Population growth rate (lambda) was lower than unity when low germination values (as those expected in natural conditions) were applied. The highest elasticity values corresponded to the survival of large adults. Matrix simulations indicated that only significant increases in fecundity and seedling survival resulted in positive lambda values. (C) 2002 Elsevier Science Ltd.