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 , Monotropoideae, Ericaceae) in two areas of the Sierra Nevada of Californi a that are similar to 180 km apart. To identify the fungal symbionts associ ated with these plants, we first analyzed restriction fragment length polym orphisms (RFLPs) of the internal transcribed spacer region (TTS) of the Fun ai nuclear ribosomal repeat. Fungal ITS-RFLPs were successfully produced f rom 57 of the 76 plants sampled, and all symbionts shared the same DNA frag ment pattern. The morphology of S. sanguinea mycorrhizae was consistent wit h that expected from a Rhizopogon species in section Amylopogon. To confirm and refine this identification, a total of six fungal ITS sequences were d etermined from S. sanguinea mycorrhizae. These sequences were analyzed toge ther with right existing and eight newly determined ITS sequences from Rhiz opogon section Amylopogon. The newly determined sequences include an ITS se quence from the fungal symbiont of pine drops (Pterospora andromedea, Monot ropoideae, Ericaceae), a plant that was previously reported to he exclusive ly associated with the Rhizopogon subcaerulescens group. When these sequenc es were analyzed together the Sarcodes symbionts grouped tightly with sever al collections of R. ellenae including the holotype, one collection of R. i dahoensis, and one collection of R. semireticulatus. A different lineage co mprised collections of R. subgelatinosus. R. subcaerulescens, another colle ction of R. semireticulatus, and the Pterospora symbiont. We conclude that S. sanguinea associates exclusively with a single species in the R. ellenae species complex throughout our sampling range. These results indicate a mu ch higher level of specificity in S. sanguinea than was previously reported and confirm the emerging pattern that nonphotosynthetic, monotropoid plant s generally associate very specifically with a narrow range of ectomycorhiz al fungi.