Until now species concept in lichens has necessarily been based solely upon morphology and secondary-product chemistry. No parent/progeny information for the lichens existed prior to our recent demonstration of reproductive isolation and gene flow. Using the methodology developed in that study, we are examining five chemotypes of the Ramalina siliquosa complex that are starkly zoned in bands on seashore cliffs in western Europe. This group epitomizes a form of variation widespread among the lichens: Chemical races with little or no morphological differentiation have different ecologies where their geographic ranges overlap. Are such chemotypes sibling species or polymorphisms within morphological species? Since hybridization cannot yet be tested in lichen by artificial crossing, we are culturing the progeny of different chemotypes that grew side by side where zones overlap. If chemotypes are conspecific and freely interbreed, then the progeny of these haploid organisms will often match a chemotype different from the maternal one. The results of this study will offer a guide to the interpretation of many hundreds of similar chemotypes of lichens already will documented. Additionally, the methodologies developed here will make possible a new dimension of experimental research in the systematics of the lichen-forming fungi.
