Testing the “one-log-one-genet” hypothesis: methodological challenges of population sampling for the Hawaiian wood-decay fungus Rhodocollybia laulaha

Abstract

We test our “one-log-one-genet” sampling method for the Hawaiian mushroom Rhodocollybia laulaha that posits all R. laulaha mushrooms collected from a single log represent a single genet. We also examine the potential expansion of single genets beyond the confines of one log and the temporal persistence of genets in nature. Finally, we estimate error rates in AFLP scoring. To our knowledge, this is one of few examinations of naturally occurring fungal genets in the tropics and a novel report of AFLP error rates in fungi. Forty-six mushrooms from seven logs were genotyped with the IGS1 locus, two microsatellite loci and 184 AFLP loci from three primer pair combinations. One hundred fifty-three mushroom collections representing the geographic range of R. laulaha were genotyped with the IGS1 and microsatellite loci. The probabilities of two genets sharing identical multilocus genotypes by chance (without actually being the same genet) were calculated for each genotype recovered. The data suggest that R. laulaha mushrooms from one log typically represent one genet, that genets might expand beyond the confines of a single log and that a single genet may persist in a collecting site for as much as 13 y. We offer initial evidence to support the “one-log-one genet” sampling method and the idea that R. laulaha vegetative expansion and persistence in nature might be common. In addition, we caution against exclusive use of AFLP loci for identifying fungal genets due to relatively high error rates in scoring.

• AFLP
• dikaryon
• genet
• Rhodocollybia saprotroph

Acknowledgments

We thank Dr Kevin Feldheim and the Pritzker Laboratory for Molecular Systematics and Evolution at the Field Museum in Chicago and the University of Hawaii, Hilo, where collections were processed. We also thank Dr Dennis Desjardin and the Harry D. Thiers Herbarium at San Francisco State University for collection loans. Keirle thanks the distinguished members of his dissertation committee, Drs Jerry Coyne, Shannon Hackett and Leigh van Valen. Keirle also thanks the financial support that made this project possible: the University of Chicago Committee on Evolutionary Biology Hinds Research Funds, the Mycological Society of America Clark T Rogerson Award and the University of Chicago CEB GAANN (Graduate Assistance in Areas of National Need) Fellowship.