Regional specialization of Sarcodes sanguinea (Ericaceae) on a single fungal symbiont from the Rhizopogon ellenae (Rhizopogonaceae) species complex

We have sampled the mycorrhizal roots of 76 snow plants (Sarcodes sanguinea, Ericaceae) in two areas of the Sierra Nevada of California that are approx. 180 km apart. ITS-RFLPs were produced from the fungal symbionts either directly from roots using fungus-specific PCR primers or indirectly after isolation in axenic culture. In total, fungal ITS-RFLPs were successfully produced from 57 plants sampled, and all symbionts shared the same fragment pattern. The morphology of S. sanguinea mycorrhizae was consistent with that expected from a Rhizopogon species in section Amylopogon. To confirm and refine this identification, a total of 6 fungal ITS sequences were determined from S. sanguinea mycorrhizae. These sequences were analyzed together with 7 existing as well as 8 newly determined sequences from Rhizopogon section Amylopogon. The newly determined sequences include an ITS sequence from the fungal symbiont of pine drops (Pterospora andromedea, Ericaceae), a species that was previously reported to be exclusively associated with the Rhizopogon subcaerulescens group. When these sequences were analyzed together, all samples from S. sanguinea grouped tightly with collections of R. ellenae and R. idahoensis, and were distinct from the lineage comprising collections of R. semireticulatus, R. subgelatinosus, R. subcaerulescens, and the P. andromedea symbiont. We conclude that S. sanguinea associates exclusively with a member of the R. ellenae species complex throughout our sampling range. These results show a much higher level of specificity in S. sanguinea than was previously reported.