Effects of latitudinal and elevational gradients exceed the effects of between-cytotype differences in eco-physiological leaf traits in diploid and triploid Hieracium alpinum

Abstract

Polyploidy may affect a species’ eco-physiology, which might, in turn, trigger a shift in the distribution of its cytotypes. The arcto-alpine Hieracium alpinum (Asteraceae) encompasses two geographically allopatric cytotypes: diploids occurring in the South-Eastern Carpathians and triploids occupying the remaining, much larger part of the species range. We ask whether the natural populations of these two cytotypes, growing under partially different biotic and abiotic conditions, also differ in selected eco-physiological traits. To answer this question, we analyzed specific leaf area, foliar carbon (C) and nitrogen (N) contents, and their stable isotope compositions in plants sampled in 27 populations across the species range. Our results did not show any differences in these traits, except foliar N content being significantly higher in diploids. This pattern was mostly driven by the Scandinavian triploid populations exposed to significantly lower amounts of solar radiation and precipitation during the growing season when compared to the continental populations. As a consequence, in addition to lower foliar N content, the Scandinavian populations exhibited also lower foliar C content, but higher C/N ratios than continental populations regardless of their cytotype. Across the species range, foliar N and C contents were positively associated with the amount of precipitation, whilst δ15N was positively associated with temperature and negatively with the surrounding species richness and vegetation cover. Significantly lower values of δ13C in Scandinavian populations are likely the effect of increased atmospheric pressure due to the lower elevational position of Scandinavian sites. Reproductive output was positively linked to amounts of foliar nitrogen and δ15N. Our data thus show that (1) the latitudinal-driven abiotic and biotic factors affected eco-physiological traits in significantly larger extent than ploidy level and that (2) continental and Scandinavian populations, though all confined to the alpine belt, considerably differ in their eco-physiology likely reflecting different adaptation strategies.