Aim: Changing climates can influence species range shifts but the mechanisms are not fully known. Using a model species, we conducted a global analysis of plant cytotypes and climate to determine whether this relationship influences population distributions, hypothesizing that smaller genomes are more common in greater environmental stress regions.
Taxon: The cosmopolitan macrophyte Phragmites australis (Cav.) Trin. ex Steud. (Poaceae)
Results: After accounting for potential spatial autocorrelation among source populations, we found climate significantly influenced Cx-value prevalence on continents. The relationships of Cx-value to temperature and precipitation varied according to whether plants were native or introduced in North America and Europe, and Cx-values were strongly influenced by precipitation during the dry season. A comparison of lower vs higher ploidy global Cx-values found that at extreme high temperatures and under extreme drought, plants have smaller Cx-values regardless of ploidy level.
Main Conclusions: Smaller plant monoploid genome size was associated with more stressful abiotic conditions, potentially influencing range expansions and contractions as changing climates select for genome sizes that maximize fitness.