wasp numbers by producing two distinct sets of fe-
male florets: short-styled ones, in which the ovaries
are accessible to the ovipositing wasps and can receive
an egg, and long-styled ones, which have inaccessible
ovaries and so are able to produce seeds. Styles are
not distributed bimodally in F. pertusa (Bronstein
1988b), however, or in any other monoecious fig spe-
cies (Bronstein 1992, Kathuria et al. 1995). They are
unimodal, so that a wasp with a slightly longer oviposi-
tor should have more space in which to lay eggs, re-
sulting in reduced seed production.
Another mystery is how fig wasp populations are
able to persist in light of figs' flowering phenology.
The likelihood of wasps failing to locate their only
host plant seems high, particularly in small fig popu-
lations (Fig. 8.9). Simulation models suggest subtle fig
phenological traits that should help stabilize dynam-
ics of the interaction (Bronstein et al. 1990, Anstett
et al. 1995). We documented one of these traits, pro-
longed receptivity of female florets, in F. pertusa
(Anstett et al. 1996). Another question relates to the
large community of nonpollinating wasps that devel-
ops alongside pollinators within F. pertusa (Bronstein
1991) and other figs. These include gall-formers, para-
sites, and predators; some are close relatives of the
pollinators, and many are as species specific on figs
as the pollinators themselves. Their natural history
is poorly known, and research on their impact on the
ecology and evolution of the pollination mutualism
is needed (West and Herre 1994, Machado et al. 1996,
West et al. 1996).
Although the pollination biology of F. pertusa is
broadly representative of monoecious figs, there are
many fascinating but poorly understood differences
among fig species. Ficus crassiuscula has at least five
times more florets per fig than F. pertusa (although
far fewer figs per tree), which may have important
consequences for fig-wasp and wasp-wasp interac-
tions (Herre 1987,1989,1996). Ficus tuerckheimii, the
most common Monteverde fig, is unusual in havingFigure 8.9. Hypothetical flowering sequence of a four-tree population of a fig species
such as Ficus pertusa in Monteverde. Wasps arrive at the tree during a short interval,
pollinate, and lay their eggs (female or pollen-receiving phase); seeds and wasps
develop within figs for about two months; the pollinator's offspring mate and depart
with pollen during another brief interval (male or pollen-dispersing phase). Because
free-living wasps live only a day or two, the male phase of the tree they leave must
correspond in time to the female phase of a nearby tree if those wasps are to make the
transit successfully. If any one of these trees were absent, then the local pollinator
population would go extinct during the time period shown. For example, if tree 1 were
absent, then wasps departing tree 3 would go extinct, and no pool of developing or
mature wasps would remain.272 Plant-Animal Interactions