Diversity patterns of life forms and phenolic profiles of endemic Nepeta plants along an aridity gradient of a high-mountain zone in Central Asia

Diversity patterns of life forms and phenolic profiles of endemic Nepeta plants along an aridity gradient of a high-mountain zone in Central Asia

For the first time, the diversity of life forms and phenolic profiles of five high-altitude species of Nepeta endemic to Central Asia were studied by cluster analysis and principal component analysis. We revealed effects of climatic factors on the average number of short modules and the average length of long modules making up the perennial axis of the plant as well as on concentrations of cinnamic and chlorogenic acids, cynaroside, isoquercitrin, and total phenolics. The significance of edaphic factors was also shown. The species inhabiting stony and movable substrates form mainly long modules (N. densiflora, N. kokamirica). Under conditions of local moistening, life form with maximum length of long modules develops (N. transiliensis), whereas grasscovered soils promote the formation of short modules (N. mariae and N. pulchella). The findings made it possible to reconstruct the course of evolutionary transformations of life forms for the studied Nepeta species. The phenolic profiles were species-specific, but their geographic variation does not match the geographic variation of morphological traits. The highest concentrations of isoquercitrin and total phenolic compounds in N. densiflora (12.0 and 56.7 mg·g-1 dry weight) - the species presumably closest to the ancestral form - indicate a decrease in the quercetin level during aridization in the course of evolution. The phenolic profile of this species, also characterized by high concentrations of chlorogenic and rosmarinic acids and of luteolin glycosides, is described for the first time in the genus and means that N. densiflora is a unique resource for therapeutic applications.