The family Dipterocarpaceae includes 470 tree species from 13 genera in South and South-East Asian tropical forests (Ashton 1982). Many dipterocarp species in aseasonal lowland rain forests of western Malesia flower synchronously during masting (or general flowering) events, which usually occur at irregular intervals of 2–10 y (Ashton et al. 1988). Very few individuals flower at other times, and successful recruitment of seedlings is limited to those masting events (Ashton et al. 1988, Curran et al. 1999).

The Dipterocarpaceae in South-East Asia are known for their strict mast fruiting. During fruiting, pre-dispersal seed predation by insects contributes to mortality of dipterocarp seeds. We documented the community structure of insect seed predators on 11 Shorea species in Peninsular Malaysia. Fruits were sampled sequentially throughout seed development, and 2144 and 1655 individuals of seed predator weevils and moths were collected in two mast-fruiting events. Four weevils: Nanophyes shoreae, nanophyid sp. 1, Alcidodes dipterocarpi and Alcidodes humeralis, and one moth Andrioplecta shoreae were abundant in seeds of the Shorea species. The proportion of N. shoreae to the total predators became larger in the latter fruiting event than the former while that of Alcidodes spp. became smaller. The predator species composition changed during seed development; nanophyid spp. emerged from immature fruits while Alcidodes spp. emerged from mature fruits. Andrioplecta shoreae emerged from both immature and mature fruits. The level of host specificity measured by Kullback–Leibler distance was low for most predator species in both events. Predator species composition of many Shorea was similar to each other due to the dominance of N. shoreae though it might gradually differ with the phylogenetic distance between hosts. In conclusion, predator species composition of Shorea varied during seed development within a host rather than among hosts. Intermittent synchronized fruiting by congeneric Shorea trees would be advantageous to avoid pre-dispersal insect seed predators, and contribute to their reproduction.

The central Ituri Forest of Zaïre is characterized by monodominant stands of Gilbert-iodendron dewevrei (mbau forest) within a matrix of mixed forest where Julbernardia seretii is subdominant. Both species produce supra-annual, synchronous (mast) seed crops. The relationship of mast seed production to monodominance for the two tree species was evaluated by investigating: (1) the relationship between seed density and seed survival, (2) the relative impact of mammal versus insect seed predators in high and low seed density areas, and (3) post-germination survival in the understorey. For the latter, tagged seedlings were monitored over 10 years and both species were censused in different understorey size classes. Percentage seed survival was significantly greater for Julbernardia (but not for Gilbertiodendron) in areas of high conspecific seed density. Generalist fruit- and seed-eating mammals were the principal predators on seeds of both species when removed to areas without seed-fall. In mast areas high seed densities appeared to satiate mammalian seed predators but not the specialized beetle seed predators that were the major cause of seed destruction. Gilbertiodendron seedlings survived longer in the forest understorey than did seedlings of Julbernardia. Furthermore, Gilbertiodendron made up a greater proportion of the larger subcanopy size classes in monodominant forest than did Julbernardia in mixed forests. These results suggest that, irrespective of mortality to seeds, the ability to persist in the understorey may confer on Gilbertiodendron a greater probability of reaching and dominating the canopy.

Nanophyes shoreae is a pre-dispersal fruit-predator of several species of Dipterocarpaceae. The timing of oviposition of this weevil was monitored in six trees in Pasoh Forest Reserve, West Malaysia from September 1986 to February 1987. A flowering event occurred during this period. Oviposition started within 12 days after peak anthesis, and continued within any one tree for 11–39 days. Host trees of N. shoreae flowered over a 75 day period. Intra-specific flowering synchrony was high but different species flowered sequentially. The behaviour of N. shoreae and the period of the oviposition ‘window’ strongly suggest that this pre-dispersal fruit-predator ‘tracks’ the sequence of flowering shown by its host species. The implications for predator satiation through mass-flowering of the Dipterocarpaceae are discussed.

We examine the density- and distance-dependent seedling survival of Philenoptera sutherlandii, a common pod-bearing and dehiscent legume (Fabaceae) in Ongoye Forest, South Africa. Short-range ballistic dispersal causes seed to fall beneath the parent tree, where density- or distance-dependent mortality effects are expected to be concentrated. One hundred and eighty marked seedlings were monitored in a 0.5-ha plot containing 30 adults. Our survival data do not support the escape hypothesis. Predation levels declined with increasing seedling density (positive density-dependent survival), but seedling survival after 15 mo was not distance-dependent. Nevertheless, a unimodal (hump-shaped) recruitment curve, typically associated with decreasing seedling density and increasing seedling survival with distance, was observed. In the context of ballistic dispersal, this recruitment curve may indicate a hump-shaped dispersal kernel with predator satiation at high seedling densities near a parent tree. This recruitment curve likely arises because generalized insect seedling predators while attracted to the adult trees also tend to forage farther away. Short dispersal distances, in turn generate the high densities needed to satiate seed and seedling predators. Predator satiation results in long-term survival rates in P. sutherlandii similar to more widely dispersed and less common tree species.

The role of white-tailed rats (Uromys caudimaculatus) as dispersers of seeds of the Australian tropical rain forest tree Beilschmiedia bancroftii, (Lauraceae) was investigated by following the fates of seeds and seedlings over 2 y. Fruits of this tree are too large to be consumed by any avian frugivore except the southern cassowary (Casuarius casuarius), and the only other native mammal capable of dispersing the seeds is the musky rat kangaroo (Hypsiprimnodon moschatus). However, neither of these species has been documented to disperse the seeds of this tree. During a mast year, white-tailed rats cached seeds an average of 13 m from parent trees in a variety of microsites. Although none of the 61 cached seeds followed in this study survived to germination, comparison of seed, cache and seedling distributions suggested that most seedlings arose from rat-cached seeds. White-tailed rats cached seeds in both mast and non-mast years, but the time seeds remained on the forest floor and in caches was significantly shorter in non-mast years, suggesting that synchronous seed production increases the probability that some caches survive to germination. Because white-tailed rats are the most common and widespread native mammal capable of dispersing large-seeds, this study suggests that they may play an important role in the seed and seedling dynamics of large-seeded tree species in Australian tropical rain forests.