Diploid hybrids have retained their genetic and morphological identites throughout their Central European range, and thus no indications for diploid backcrossing were found. The triploid hybrids have probably originated from backcrossing between a diploid gametophyte of a hybrid (derived from a diplospore) and a haploid gametophyte of a diploid parental species. By repeated crossing events, reticulate evolution patterns arise that are similar to those known for a number of ferns.

A Diphasiastrum taxon being morphologically intermediate between D. alpinum and D. tristachyum is described as D. oellgaardii. During gel isoenzyme analyses, glucose‐6‐phosphate isomerase and esterase turned out to be electrophoretic markers testifying the hybrid origin of D. oellgaardii. In Europe, where three parental species (D. alpinum, D. complanatum and D. tristachym) occur, D. oellgaardii is the third taxon of hybrid origin besides D. issleri and D. zeilleri. Problems of reproductive biology of these taxa are discussed.

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