Spatio-temporal, variations in post-dispersal seed fate

The post-dispersal fate of Chrysophyllum lucentifolium (a canopy tree; Sapotaceae) seeds was analyzed in French Guiana over three consecutive years. Experiments using 750 thread- marked seeds were performed to investigate seed removal, predation, and caching by terrestrial vertebrates on howler monkey (Alouatta seniculus) defecation sites, where clumps of intact C lucentifolium seeds were observed. Year-to-year variations in seed fare during the peak fruiting period were considered in relation to overall fruit and seed resource availability estimated by a raked-trail survey. The effect of two forest areas, which differed in soil and floristic composition, was examined with conspecific fruiting tree density as a covariant. Exclosure versus open treatment was used to discriminate small rodents (not larger than a spiny rat) from other vertebrates. The presence of fresh howler dung did not affect seed fate after 20 days as shown by comparisons between defecation sites and control during the first year. There was a significant effect of year on the percentage of seeds remaining after 20 days. Low seed removal in 1995 and 1996 (compared to 1997) corresponded to higher overall fruiting and higher fruiting of C lucentifolium, or the presence of alternative resources for rodents. All effect of forest area was observed on the seed removal rate, which varied with years and protection. Comparatively, an effect of forest area on the percentage of seeds lost was observed in 1996 and an effect of treatment on the percentage of seeds eaten was seen in 1995. The mode of seed caching Suggested that spiny rats were the main seed remover. Results of this study suggest that greater seedling recruitment may Occur when large fruit crop and high howler dispersal co-occur with a lower impact of rodents (i.e., when rodents are saturated by abundant and diversified fruit resources such as in 1995). Such event synchrony, however, is highly unpredictable after only three years of study.