Data from: Complex indirect effects of epiphytic bromeliads on the invertebrate food webs of their support tree

Ecosystem engineers are species that affect others through the provision
of habitat rather than consumptive resources. The extent to which
ecosystem engineers can indirectly affect entire food webs, however, is
poorly understood. Epiphytic tank bromeliads (Bromeliaceae) are ecosystem
engineers that are common throughout the Neotropics, and are associated
with a variety of predatory arthropods. Here, we examine if bromeliads, by
increasing predator densities, indirectly benefit their support tree
through reduction in herbivorous insects and leaf damage. We observed and
manipulated bromeliad densities in Costa Rican orange orchards, and
measured impacts on leaf damage and arboreal and bromeliad invertebrate
communities in two different seasons. Our results show that bromeliads are
associated with predatory and herbivorous invertebrates but not leaf
damage. Bromeliads were correlated with increased densities of their
associated predators, especially ants and hunting spiders, but we could
not confirm a causal link. Associations with bromeliads changed over time,
with seasonal shifts interfering with responses to our manipulations.
Bromeliads had a reduced association with predators in the dry season.
Moreover, a null association between bromeliads and herbivorous
invertebrates in the dry season unexpectedly became positive in the wet
season. In summary, we have only limited evidence that bromeliads
indirectly promote the top-down control of arboreal herbivores; instead,
our manipulations suggest that bromeliads increase herbivore densities in
the wet season. This research suggests that although bromeliads may act as
ecosystem engineers, indirectly influencing the invertebrate food web on
support trees, their effects are trophically complex and seasonally
dependent.