Implications of Phylogenetic Studies for Conservation of Genetic Diversity in Shiitake Mushrooms

We consider the impact o f recent molecular phylogenetic analyses on conservation issues for shiitake mushrooms. Based on mating compatibility, shiitake has been considered a single species, Lentinula edodes sensu lato. Phylogenetic analyses o f ribosomal RNA internal transcribed spacers (Htbbett et aL 1995), however, suggest that shiitake is composed o f f our distinct lineages. Thus, under a phylogenetic species concept, f o u r species o f shiitake should be recognized. A classification o f shiitake based on a phylogenetic species concept would convey information about evolutionary relationships and distribution of genetic variation, whereas a classification based on a biological species concept would lack such information. This is a clear case in which new insights into phylogenetic relationships can be used to target areas for conservation action and formulate international agricultural policies. At the heart o f our argument is the belief that the basic units o f both taxonomy and conservation should be unique evolutionary lineages o f organisms identified through phylogenetic studies. Implicaciones de estudios filogen6ticos en la conservaci6n de la diversidad gen~tica de hongos shiitake Resumen: En este trabajo consideramos el impacto de andlisis filogemSticos moleculares recientes en la conservaci6n de hongos shiitake. Con base en la compatibilidad reproductiva el hongo es considerado como una sola especie, Lentinula edodes sensu lato. Sin embargo, el andtisis de espaciadores transcritos internos del ARN ribosomal sugiere que el shiitake esta compuesto por cuatro linajes distintos. Asf, de acuerdo con el concepto filogendtico de especie, se deben reconocer cuatro especies distintas de shiitake. Una clasificaci6n de shiitake basada en el concepto filogendtico de especie proporcionarfa informaci6n acerca de las relaciones filogendticas y la distribuci6n de la variaci6n gen~tica, mientras que una clasificaci6n basada en el concepto biol6gico de especie carecerfa del tal informaci6n. Este es un claro ejemplo de como se pueden utilizar nuevas percepciones de los relaciones filogendticas para detectar dreas en las cuales desarrollar acciones de conservaci6n, asf como formular politicas agrfcolas internacionales. En el centro de nuestra argumentaci6n yace la creen-. cia de que las unidades bdsicas de la taxonomla y de la conservaci6n deben ser los linajes evolutivos identificados por medio de estudios filogen6ticos. Cultivation and Taxonomy of Shiitake Shiitake mushrooms are wood-decaying basidiomycetes that are commonly used in northeast Asian cooking. In China a primitive form of shiitake cultivation was in practice perhaps as long as 1000 years ago (Chang & Address correspondence to D. S. Hibbett, email d_hibbett@ harvard.edu Paper submitted June 30, 1995; revised manuscript accepted November 28, 1995. Miles 1987; Ito 1978). Modem shiitake cultivation has been made possible by advances in the understanding of basidiomycete life cycles and improvements in culturing techniques (Przybylowicz & Donoghue 1988). In contemporary shiitake farming "spawn" is produced by propagating vegetative fungal mycelium on sawdustbased media at centr'4Uzed facilities that are equipped with large-scale autoclaves, microbiological culturing facilities, and other m o d e m laboratory equipment. The spawn is then used to iinoculate specially harvested logs or sawdust-based frudting media in plastic bags2 For mushroom product ion inoculated logs or bags are typi-