• Borneo;
  • climate;
  • dioecy;
  • mutualism;
  • sexual specialization

The phenology of a dioecious fig (Ficus fulva, Reinw. ex Bl.; 25 female, 26 male trees) was studied at Lambir Hills National Park, Sarawak. Dioecious fig phenology provides an excellent opportunity to investigate the influence of climate and sexual specialization on the obligate fig–fig pollinator/ovule parasite interaction. Leaf phenology was strongly correlated between sexes. Trees dropped leaves during drought and initiated new leaf growth after the renewal of rain. Before the production of large crops of syconia, trees shed their leaves and then new leaves and syconia were initiated together. Syconia were produced in synchronous crops with asynchrony between trees maintaining a relatively even production of syconia within the tree group. Syconia abortion on male but not female trees, was negatively correlated with the proportion of trees with male phase syconia. A severe drought in early 1998 significantly disrupted the phenology thereafter. The duration of crop development was approximately twice as long on female trees as on males, and total syconia production was much higher on male trees. Plots of syconia diameter versus dry weight suggest sexual specialization in the investment profile during crop development. Male trees also sometimes produced a small crop of syconia immediately before a large crop, probably to supply wasps for the main crop. Sexes had different growth strategies with male trees growing more as small individuals and slightly delaying reproduction. Diameter at breast height was significantly correlated with total syconia production in male trees but not in females. Syconia production was best predicted by canopy width.