Ecological niche differences between two polyploid cytotypes of Saxifraga rosacea

Authors:

Lucile Decanter 1,2,4,5, Guy Colling 2, Nora Elvinger 2, Starri Heiðmarsson 3, and Diethart Matthies 4 1 Fondation Faune-Flore c/o Musée national d’histoire naturelle, 25 rue Münster, L-2160 Luxembourg, Luxembourg 2 Population Biology and Evolution, Musée national d’histoire naturelle, 25 rue Munster, L-2160 Luxembourg, Luxembourg 3 The Icelandic Institute of Natural History, Borgir vid Nordurslod, 600 Akureyri, Iceland 4 Unit of Plant Ecology, Department of Biology, University of Marburg, Karl-von-Frisch-Straße 8, D-35043 Marburg, Germany 5 Author for correspondence (e-mail: lucile.decanter@mnhn.lu)

Source:

Decanter, L., G. Colling, N. Elvinger, S. Heiðmarsson, and D. Matthies. 2020. Ecological niche differences between two polyploid cytotypes of Saxifraga rosacea. American Journal of Botany 107(3): 423–435. doi:10.1002/ajb2.1431

Abstract:

Premise
Different cytotypes of a species may differ in their morphology, phenology, physiology, and their tolerance of extreme environments. We studied the ecological niches of two subspecies of Saxifraga rosacea with different ploidy levels: the hexaploid Central European endemic subspecies sponhemica and the more widely distributed octoploid subspecies rosacea.

Methods
For both cytotypes, we recorded local environmental conditions and mean plant trait values in populations across their areas of distribution, analyzed their distributions by niche modeling, studied their performance at two transplant sites with contrasting conditions, and experimentally tested their cold resistance.

Results
Mean annual temperature was higher in hexaploid than in octoploid populations and experiments indicated that frost tolerance of the hexaploid is lower than that of the octoploid. Reproduction of octoploids from Central Europe was higher than that of hexaploids at a transplant site in subarctic Iceland, whereas the opposite was true in temperate Luxembourg, indicating adaptation of the octoploids to colder conditions. Temperature variables were also most important in niche models predicting the distribution of the two cytotypes. Genetic differences in survival among populations were larger for the octoploids than for the hexaploids in both field gardens, suggesting that greater genetic variability may contribute to the octoploid’s larger distributional range.

Conclusions
Our results support the hypotheses that different cytotypes may have different niches leading to spatial segregation, and that higher ploidy levels can result in a broader ecological niche and greater tolerance of more extreme conditions.