The edaphic niche of ploidy-different grasses in the light of the coarse-grained data modeling and direct soil sampling

Abstract

In the framework of polyploidization, a widely discussed issue is the possibility of niche shift. Numerous studies have investigated niche differentiation among cytotypes, with some confirming distinct differences, while others finding them to be similar. Within this research project, we focus on the case of the cytotypes (2x and 4x) of Festuca amethystina L. and the closely related F. tatrae (Czakó) Degen (2x). We hypothesize that a significant change in the edaphic niche of tetraploids could be a factor that enabled them to occupy new lowland areas inaccessible to diploids which are characteristic of mountain habitats.The edaphic niche differentiation between Festuca amethystina cytotypes was determined by studying the niches’ breadths using PCA-based modeling and separate analyses of particular soil features. The modeling was based on SoilGridsTMdata, and the conclusions were compared with the results of the direct soil studies. Such a research model makes it possible to determine to what extent the data coming from the mentioned database allows for the indication of niche differentiation.Coarse-grained modeling based on SoilGridsTM data indicated a significant change in the edaphic requirements of the tetraploids, as well as pointed to the niche shift towards a higher content of sand, lower carbon and nitrogen content, and lower pH. The direct soil sampling and laboratory tests confirmed these trends and provided a more detailed understanding of the cytotypes requirements. However, no statistically significant differences were observed between cytotypes concerning soil pH, the majority of base cations, available forms of phosphorus and potassium, and the results of CHN elemental analysis. While the direct soil sampling did not reveal significant differences, the analyses based on the niche modeling, considering a wide background area in Central Europe (using SoilGrids data), captured significant variations. This comprehensive approach allowed us to uncover a highly logical pattern of niche shift, which indicates that tetraploids are predisposed to extend their geographical range to post-glacial lowland areas.Additionally, Festuca amethystina tetraploids display a wider edaphic niche breadth than their closely related and hypothetical ancestor Festuca tatrae. The decision to include the latter reduced the probability that the obtained result of the significant increase of the tetraploid edaphic niche was a simple result of hybridization.