DEMOGRAPHY OF THE VEGETABLE IVORY PALM PHYTELEPHAS-SEEMANNII IN COLOMBIA, AND THE IMPACT OF SEED HARVESTING

1. The demography of the vegetable ivory palm Phytelephas seemannii wa s studied on the Pacific coast of Colombia and a female-based matrix m odel was used to determine the proportion of seed that can be sustaina bly harvested from the population. 2. The density of the palm stands r anged from 240 to 420 adult palms ha(-1). The sex ratio was 1:1 and pa lms of both sexes produced leaves at the same rate. Seedlings produced 1.2 leaves per year on average, juveniles 1.8, and adults 6.1--7.4. 3 . Adult females had fewer leaves than males (18.5 vs. 21.3 on average) . Leaves of females lasted about 2.7 years in the crown, those of male s about 3.2 years. 4. Stems creep on the ground, growing at the apex a nd often dying behind, the extant portion not always reflecting the pa lm's total age. The longest stem of a female palm in the study plots w as 2.5 m, corresponding to an 'extant' age of 85 years; the longest st em recorded was that of a male (outside the plots) 10.5 m In long, cor responding to an 'extant' age of 184 years. These figures reflect diff erences in growth habit, not in longevity. 5. Reproduction began at ab out 24 years, when the palm still lacked an above-ground stem. 6. The population growth rate lambda was 1.059, and was most sensitive to cha nges in survival of juveniles and adults, and relatively insensitive t o changes in fecundity and growth. 7. River channel migration is the m ost important cause of adult mortality. Phytelephas seemannii is appar ently an efficient colonizer of the understorey in the late phases of riverine forest succession. 8. The population call tolerate a harvest intensity of 86% of all seeds before lambda decreases to the equilibri um level of 1.00. Monitoring of the populations under intensive harves ting is required.