Post-zygotic isolation between allopatric mating groups of Closterium ehrenbergii Meneghini (Conjugatophyceae)

Abstract

Laboratory crosses between clones of three mating groups of Closterium ehrenbergii Meneghini were studied to ascertain the possibility of gene flow between these two pairs of closely related mating groups of allopatric occurrence. Since only an extremely low percent survival of F₁ progenies was obtained along with the morphological abnormality in zygospore germination and its products, it was concluded that there is no possibility of gene flow between them, even if the geographical barrier were to break down. Groups A, B and H of C. ehrenbergii are considered closely related to each other from partial sexual compatibility, but they should be recognized as three different biological species because of the presence of strong reproductive isolation demonstrated by hybrid inviability and weakness.