IV. Plant-Animal Interactions

Spider wasp pollinating palmetto flowers The Lake Placid scrub mint is an endangered plant, which lives only in a small area near the town of Lake Placid. Other kinds of endangered scrub mints occur in other areas of Florida. In order to protect an endangered plant species it can be useful to know some details of its biology. Scientists began looking at the insects pollinating the Lake Placid scrub mint and discovered that one kind of bee-fly usually pollinates its flowers. The pollen of this plant is kept under pressure inside the pollen-bearing structures, called anthers. When the fly collects nectar from the flower, the fly's furry belly presses down on the top of these anthers. This pressure causes a little slit to open in the anther so that the pollen comes popping out onto the fly's belly. To save the Lake Placid scrub mint we need this fly. Fortunately, the fly is quite common. Nobody knows, however, what the fly larvae eat. Most likely, they are predators that attack other insects underground, but nobody really knows if these fly larvae require something special.

Placing the plant unit last in a curriculum may seem unusual since plants are so basic to all life in the scrub, just as they are everywhere on our planet. But to consider plants requires moving to new levels of complexity. The earlier activities in this curriculum were stepping-stones to this unit.

The simplest aspects of biology deal with physics, as in the physics of sand. Predation, as in ant lions and ants, is still a relatively simple topic, as long as the focus is on the mechanisms of predation and not the population dynamics of predator and prey. Decomposition introduces the idea that there are whole systems revolving around plant by-products. Now it is possible to consider the much larger systems of plant-animal interactions. This curriculum has been slowly building increasing levels of complexity.

Plants also express the theme of adaptations for life in the scrub in the most definitive and complex ways. Plants cannot move around freely, and must take life as it comes. Plants cannot flee fire in the scrub, so they must have specific adaptations for it. Plants cannot hide from the sun in the heat of the day. They cannot roam around like animals and search for concentrations of nutrients. Although the adaptations of plants for life in the scrub are clearly displayed in leaf and growth forms, some adaptations are difficult for students, or anyone else, to imagine. Therefore, it makes sense to introduce plant adaptations after you and your students have thoroughly explored the concept of adaptation.

This section concentrates on two groups of plants that are very important in the Florida scrub habitat--the palmettos and the oaks. Unfortunately, dozens of other groups of plants and their interactions with animals are not mentioned. By developing the stories of palmettos and oaks in depth, we hope to more clearly convey the number of complex relationships in the scrub than if we quickly presented many plants. Observant students will probably notice additional plant-animal relationships. These students can be encouraged to design little research projects to explore these relationships. Since many of the relationships between plants and animals in the scrub have not been studied by scientists, a research project undertaken by a student could easily grow into an exciting original project for a science fair or a school research project. These could even become part of a new curriculum! The examples of pollination ecology mentioned below should give you an idea of all the things that could be studied.

At least three species of pawpaws occur in Florida Scrub, including the endangered Four-petal pawpaw, found in scrubs along the East Coast of Florida. Pawpaws bloom in the spring and have big white flowers that are not attractive to bees and butterflies. The flowers produce a peculiar fruity or musky smell that attracts beetles, especially flower scarabs and longhorn beetles.

These beetles feed on part of the center of the flower and carry pollen from one plant to another. Although these beetles fly away quickly when disturbed, you can easily catch one in a clear plastic food storage bag and examine it for a moment before releasing it. (A plastic bag should be in every naturalist's field kit!) Students can identify the pollen producing flowers by sniffing at each flower (without touching it) for the characteristic fragrance. To catch beetles that may be feeding in the flower, place a bag gently over the flower, then tap the flower or move its inner petals. If beetles are feeding in the flower, they will tumble out and buzz around the bag like bees or wasps. Because these beetles fly and buzz like stinging insects but do not sting, they provide a good example of behavioral mimicry.