Infraspecific variation in two species of aquatic hyphomycetes assessed by RAPD analysis

Abstract

During a survey of aquatic hyphomycetes isolated from foam patches in a stream of the Central Region of Spain, random amplified polymorphic DNA (RAPD) profiles were used to analyse the infraspecific variability within the populations of the two dominant species, Heliscus lugdunensis and Articulospora tetracladia . Thirteen foam samples were collected along ∼ 1 km of the stream course and strains of these two species were cultured from single conidia. More than 100 isolates of each species were subjected to PCR under low-stringency conditions, using two primers derived from consensus sequences of the 5·8S rRNA gene. The Heliscus and Articulospora strains could be divided into seven or five different RAPD types, respectively, each group containing at least four isolates. Up to 10 of these different genotypes could be detected in the same foam sample. The distribution of these RAPD types among the foam samples seems to be random. These results suggest the presence of a relatively stable pool of fungal genotypes colonizing the plant substrates along the stream. However, the mechanisms of fungal dispersion occurring in freshwater courses could also account for the high percentage of RAPD groups shared among relatively distant foam patches.