Bromeliads are a Neotropical family of largely terrestrial or epiphytic monocots. In general, their growth habit is made up of spirally arranged leaves. In some species, the leaf bases overlap to form water-retaining pockets, or phytotelmata. These reservoirs also collect detritus, such as falling leaves and other organic matter, and this becomes the habitat for many organisms, including the larval stages of several species of insects. Bromeliads are a natural microcosm, allowing us to study interactions within a community of bromeliad organisms or to trace the flow of nutrients through the system. We also conduct research on some of the fascinating creatures that are associated with bromeliads at some stage of their life histories.

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The detritus in phytotelmata is the base of the food web. Some species of insect larvae process this plant matter, mechanically degrading different sized leaf pieces, while others are specialized for scraping off surficial algae. This leads to a processing chain of organisms that are reliant on each other. At a higher trophic level, there are organisms which prey on the detritivores, and there may be higher predators which prey on these intermediate predators.
The relationships in this food web can be investigated by experimental manipulation. In one experiment, the larvae were removed from the bromeliads (above right), sorted (using the diagrams shown on this website) (above left and left), and artifical food webs were constructed in enclosures with a known number and composition of individuals. For enclosures, we used centrifuge tubes which were then placed back into bromeliad tanks to simulate as natural an environment as possible (right). The tubes had mesh-screened holes in them to allow for water exchange while keeping out unwanted organisms. Some treatments in our artificial food webs removed organisms from the proccessing chain while other treatments removed predators. By seeing how the remainng organisms responded to these changes in terms of survivorship and growth rate, we can determine the strength of the relationships within the community.

Nutrients
Bromeliads obtain nutrients from the detritus in the phytotelmata. The availability of these nutrients is a major determinant of bromeliad growth. Some bromeliads were isolated and fertilized (left) with various treatments of nitrogen and phosphorus, and it was found that growth was primarily limited by nitrogen.
The role of the insect community in the flow of nutrients was also considered. In another experiment, bromeliads were isolated in mesh enclosures with a known larval insect community (below left). Detritus enriched with N¹⁵ (right) was placed inside all bromeliads. Treatments included bromeliads with no insect larvae, detritivore larvae only, and detritivore and predators. The rate of detrital decomposition was monitored and relative effectiveness of nitrogen cycling in the various scenarios could be measured.