Mating types and reproductive isolation inClosterium ehrenbergii meneghini

Abstract

Numerous clones ofClosterium ehrenbergii Meneghini were isolated from soil or liquid samples from various localities and clonal uni-algal or axenic cultures were established. Mating types of these clones were determined by crossing with tester clones. No homothallic clone has been encountered, even in such an extensively surveyed area as that in Japan. By some unknown factors, mating type ratios have been found to deviate largely from 1∶1 in some populations in liquid samples, but not in populations from soil samples. Representative clones from each locality were intercrossed with those from other localities in all possible combinations. Seven reproductively isolated groups were recognized on the basis of capability and frequency of zygospore formation. Cooccurrence of more than two groups in the same sample has been encountered in five cases out of 41 localities surveyed. In four cases the two groups found together have turned out to be completely isolated but in the last case two groups of incomplete isolation were found with the other group of complete isolation.