Biological Species in Pleurotus
RONALD H. PETERSEN, KAREN W. HUGHES, AND NADEZHDA PSURTSEVA
Genetic Isolation
Over the years, data have accumulated to support (or reject) reproductive isolation of biological taxa. For example, Pleurotus populinus was proposed after such tests proved the genetic coherence but extra-specific intersterility of collections from western North America chiefly on Populus (Vilgalys et al.,1993). Similarly, worldwide pantropical isolates of P. cystidiosus were found to be intercompatible, but cultures labelled as P. smithii (Mexico) were incompatible with the others, and Zervakis (1998) concluded that P. smithii was a discrete biological unit. In the same way, the several color forms of P. djamor were proven to share a common gene pool (Nicholl, 1977).
Such data are produced in two ways: a) pairing experiments among monokaryon isolates of several collections in all combinations (in this lab termed a "round-robin"); and/or b) pairing of monokaryon isolates of a single collection against a library of monokaryons from all other available taxa (in this lab termed a "recognition grid"). The latter is usually used to identify a new acquisition, but Petersen (1995) discussed the efficacy of this method for other uses.