Abstract:
Predators are often more sensitive to habitat size than their prey and frequently
occur in only the largest habitats. Four explanations have been proposed for this pat-
tern: (a) Small habitats do not have enough energy to support higher trophic levels;
(b) small habitats are less likely to contain particular prey required by specialist preda-
tors; (c) small habitats are risky for predators with slow life histories or large body
sizes; and (d) small habitats are numerically unlikely to be colonized by regionally rare
species, such as predators. We critically examine these four hypotheses in relation
to the predatory damselfly larva, Mecistogaster modesta Selys. (Pseudostigmatidae),
which occurs almost exclusively in bromeliads
>
100ml in capacity. We synthesize
multiple years of survey data and three manipulative experiments from the Área de
Conservación Guanacaste, Costa Rica, to conclude that damselflies do not occur in
small bromeliads due to their higher risk of desiccation—not because of energetic
limitation, trophic specialization, risk of terrestrial predation, or pure numerical ef-
fects. These results suggest that recent and predicted declines in precipitation in
northwestern Costa Rica may further restrict bromeliad occupancy by damselflies,
with cascading consequences for the rest of the aquatic food web.
Abstract in Spanish is available with online material.
