Fungi often have been suggested as determinants of plant diversity, and plant diversification has been implicated as a major factor affecting the diversity of beetles and other insect groups. Direct relationships between fungi and insect evolution, however, remain under appreciated. Gut-inhabiting fungi, including yeasts, are known to be essential to the nutrition of some insects. The current study is based on results of previous NSF supported research in which the PIs isolated about 200 new species of yeasts out of 650 isolates from digestive tracts of beetles in 27 families in selected Panamanian and USA localities, an increase of 30% of all known yeast species. Statistical analyses estimate that resampling of only the previously sampled restricted habitats could produce additional undescribed taxa to increase current yeast numbers from all habitats worldwide by 50%. The discovery of the great diversity of undescribed yeasts in association with beetles is stunning, especially when one extrapolates beyond the highly restricted taxonomic, temporal, ecological, and geographical scope of this study. Phylogenetic analyses placed the beetle gut yeasts in at least 45 independent clades among all known yeasts with clustering of major insect-associated groups, suggesting high yeast diversity arose by occasional horizontal transmission in common habitats and subsequent specialization with the insects. In addition to discovery of new yeast species the current study will attack physiological, ecological, and evolutionary questions, regarding the nature of the yeast-insect associations, the universality of associations worldwide, and the role that yeasts may play in habitat expansion and speciation of insects, and the PIs will use field and cultural methods as well as molecular techniques, including DNA sequencing to answer the questions.
The study will have broader scientific significance because yeasts have great potential in industrial processes. In this work the PIs discovered that yeasts associated with wood-ingesting beetles have potential in efficient conversion of plant material to fuel alcohol. Other newly discovered yeasts synthesize a wide variety of other enzymes and vitamins, and the PIs will collaborate to determine if these might be useful in industrial processes. The PIs will continue to be highly interactive and will disperse the findings of this study widely. An added benefit will be the continued training of undergraduates and graduate students in methods of modern evolutionary and ecological studies as in the previous study. In addition to the training of graduate students, the PIs were especially effective in using the previous project as a focus for training 17 undergraduates on aspects of insect-fungus associations; these included 4 men and 13 women, two of whom were minority women. All graduated students have gone to graduate or medical school; one is a George C. Marshall Scholar at Oxford University. Four papers with undergraduate authors were published, and two presentations at national meetings involved undergraduates.
