Interactions between species that benefit both species are known as mutualisms. Mutualisms are integral components of many communities and have been directly and indirectly involved in creating earth's biodiversity. Despite their importance and widespread occurrence, there is still a need to understand how mutualisms are influenced by the local community in which they exist. Mutualisms are thought to be carefully balanced interactions where the benefits of the interaction exceed the costs. This project will empirically test theoretical predictions concerning how community members affect the costs and benefits received by mutualists. The well-known pollination mutualism between yuccas and their pollinating moths will be used to test these predictions. Researchers will conduct experiments in natural populations and make genetic estimates of plant reproduction to examine how the presence of other species influences the cost-benefit ratio of this mutualism.
Results from the study will provide important tests of how mutualisms persist when mutualists simultaneously interact with a variety of species. The research will also incorporate a community perspective into a well-known interaction that is commonly used in biology textbooks as an example of mutualism and pollination. Furthermore, the research will support an educational outreach project aimed at creating a web-based teaching module for 3rd-5th grade students and will provide Florida Comprehensive Assessment Test format material for educators.
Species interactions form the basis of communities and have helped to create the rich diversity of organisms on the planet. This biodiversity possesses a largely untapped wealth of information that can be used for drug discovery, improvements in agriculture, and the invention of new technology that mimics nature. In particular, interactions between species are exceptionally important reservoirs of many natural products and applications. For instance, parasitic wasps are often used in the biocontrol of agricultural insect pests, and the stimulating effects of tea and coffee are the result of plant evolution to insect herbivory. We study how interactions between plants and insects are shaped by evolution. A key type of interaction is mutualism where both species benefit from participating in the interaction. For example, bees help plants reproduce by pollinating flowers, and in return, they receive nectar or pollen as a source of nutrition. Although mutualisms are incredibly important in natural communities, we know little about how they are influenced by other species that are also present. Since all naturally occurring mutualisms exist within a broader community of species, our current understanding of mutualism is limited. The purpose of this project was to determine how these additional community members affect mutualisms. For this project, we studied the pollination mutualism between yucca plants and yucca moths. Yuccas are only pollinated by yucca moths and yucca moth larvae feed exclusively on yucca seeds. Both the plants and insects gain in terms of reproduction, making this interaction mutualistic. Most studies of the yucca-yucca moth mutualism have focused on the pairwise interaction between mutualists; however, the mutualists also interact with a number of antagonistic insects that feed on the plants but provide nothing in return. We asked whether and how the presence of these antagonistic species could influence the mutualism. The major findings were: Antagonistic species can change how flower and inflorescence characteristics evolve. Some insect herbivores are attracted to the same plant traits as the pollinators, and because herbivores are often costly to the plant, they can influence how plant floral traits evolve. Previous research on flower traits has mostly assumed that pollinators are the sole factor that cause evolution of these characters. Antagonists that are completely dependent on yuccas cause less damage than antagonistic species that can also feed on other plant species. This suggests a role for specialization in determining how much damage a particular species might inflict on plants. Higher dependency on a plant may make some insect herbivory less costly. Some antagonistic species may actually benefit the plants through indirect interactions. For example, although a flower-feeding beetle damaged floral tissue, it also consumed yucca moth eggs, which increased seed set (the eggs would have developed into seed feeding larvae). These kinds of indirect interactions can give unexpected results and are often as important as the direct effects. Flower-feeding insects can inflict damage on plants in a variety of ways. In our system, these insects could reduce seed set by causing flowers to fall off, by consuming pollen, and by directly damaging flowers. In addition to this research project, we also created an evolution education module for 3rd-5th grade students that dovetails with a nationally recognized program run by the Archbold Biological Station in Florida (Discovering Florida Scrub). The module provides teacher materials for 15 exercises that teachers can use in their classrooms and is cross-referenced with the Florida Sunshine State Standards for science, language arts, mathematics, social sciences, and arts. Although the module is written for ecosystems found in Florida, it can be easily adapted for use in other locations. The module is available on our lab websites as well as the field station’s education website. This project trained nine undergraduate students, two graduate students, one community college faculty, and one post-doctoral fellow in experimental design and lab methods.
