Repair, growth, age and reproduction in the giant columnar cactusCephalocereus columna-trajani(Karwinski ex. Pfeiffer) Schumann (Cactaceae)

Loss of shoot-tip because of severe, but non-lethal, injury is a common event in the life-cycle of giant columnar cacti. Repair (reiteration) could adversely affect further growth and reproduction because of a reassignment of resources. We studied a population ofCephalocereus hoppenstedtiiin Central Mexico, comparing growth rates, age of first reproduction and number of flowers produced per individual in repaired and undamaged cacti. A fitted, generalized linear model, using a binomial error distribution and a logit link function, described the probability of survivorship after the cactus shoot is broken. According to this model, only individuals exceeding a certain critical height before damaged are able to survive, and also only reproductive individuals not surpassing an upper threshold height (or age) would survive. We did not find significant differences in flower production between injured and non-injured individuals. The cost of repair would imply a delay ofca60 years before the damaged cacti could resume reproduction