IMPORTANCE OF PREDATION AND GERMINATION ON LOSSES FROM THE SEED BANK OF CALDEN (PROSOPIS-CALDENIA)

Calden (Prosopis caldenia) seeds not dispersed by animals sometimes co nstitute a considerable number of seeds to the seed bank which may con tribute to the species' dissemination, The monthly change in the numbe r of viable non-animal dispersed seeds was evaluated over a one-year p eriod, We determined the percentage germination of seeds and the amoun t of predation by bruchid beetles to learn how these factors influence seed longevity, Forty eight bags containing 10 fruits were placed in 4 sites below calden tree canopies at the time of shedding (March), To monitor seed losses we randomly removed 1 bag per site every 25-35 da ys during a year, At the time of shedding, fruits contained 29 seeds, 73 +/- 5.0% which were viable and 9 +/- 2.2% attacked by bruchids, Via bility decreased to 33 +/- 22.3% one year later, Loss of viability was described by a polynomial quadratic (y = 70.12 + 0.0238 t-0.0004 t(2) (r(2) = 0.62)). Bags with germinated seeds were observed beginning in November, Percentage germinated seed increased 4.8 +/- 3.7% in the la st month of sampling, Consumption of seeds by bruchids also increased in November, but the effect was highly variable, In the last month of sampling (March in the following year), 35 +/- 18.0% of seeds were aff ected by bruchids, A predictive seed longevity model was developed con sidering climatic variables, but data were well described only until J anuary (y = 81.50-0.097 time-3.94 precipitation (r(2) = 0.66)), Undisp ersed seeds had a high rate of decay and low germination, Longevity wa s strongly affected by bruchid attack.