ИСТИНА

Gaps in morphological or genetic variability call for taxonomic level interpretation. These interpretations are sometimes far from being satisfactory. For example two vicarious species in the Galium glaucum group, G. hexanarium Knjazev and G. octonarium (Klokov) Pobed., show the morphological variability gap in the Ciscaucasia region. This phenomenon was known from 19th century, yet morphology and climatic variability comparison reveal a high level correlation. Moreover, climatic-based models have a higher percentage of explained variability than geographic-based. There is a common cline along climatic gradients for both “species”. The gap in morphological variability is an artifact of bedstraw’s geographic distribution and climatic gradient direction change in the Ciscaucasia region. That variability gap does not imply the existence of a taxonomic border.