Climate and genome size shape the intraspecific variation in ecological adaptive strategies of a cosmopolitan grass species

Intraspecific trait variation, essential to Darwin's mechanism of natural selection, has been widely examined for single characters. However, intraspecific variation of adaptive strategies which represent trade-offs among multiple functional traits has received less attention, particularly for species that are globally distributed or invasive. Grime's competitor, stress tolerator and ruderal (CSR) scheme, well validated in the context of alien species invasions, provides both the theory and quantitative methodology to investigate adaptive strategies. Here, we quantified the intraspecific CSR strategy scores of a worldwide collection of 89 Phragmites australis genotypes which were cultivated in a common garden. We assessed the relationships between intraspecific variation in CSR strategy scores, genome size and climate of origin and tested whether the invasive and native lineages differ in CSR strategies. Substantial variation in intraspecific adaptive strategy, characterized mainly in C- and S-selection, was observed. As expected, C-, S- and R-scores showed clear latitudinal clines and were strongly related to either genome size or climate of origin. Furthermore, invasive lineages were more stress adapted than native lineages. We conclude that the adaptive strategy of this perennial wetland grass varies globally, and its genotypes are surprisingly more stress tolerant in the invaded range where it was first detected ~150 years ago. Read the free Plain Language Summary for this article on the Journal blog.