How does a plant vary across its range?

Plants are not identical copies of each other; there’s variation within a species. But how do they vary? Aurélien Estarague and colleagues examined Arabidopsis thaliana to consider how it varies within its range. Understanding how the variation occurs would help understand what drives the limits of a plant’s range.

The team measured variation by examining functional traits and ecological strategies from the CSR scheme. The CSR scheme describes a plant’s investment in either competitive strategies (C), stress-tolerant strategies (S), or ruderal (colonising disturbed areas) strategies (R). They also measured how a plant responded to abiotic stress. The goal was to measure many plants and see if variation varied with latitude or from the centre to the margins.

The team compared thirty natural accessions of Arabidopsis thaliana, randomly selected among three geographical groups. The plants sourced from the Iberian peninsula formed the southern group. Plants from between 45 degrees north and 52 degrees north formed the central group in an area bounded by France, the Netherlands and Austria. Plants from Scandinavia formed the northern group.

Estarague and colleagues found both types of variation in their sample set. The plants from the northern locations had a greater stress tolerance than the more southerly plants. However, plants from the centre of the range had higher scores for competition, colonisation and fruit number. They also found that central plants had higher phenotypic plasticity for most traits.

The botanists argue that the reduction of plasticity at the margins of the range might be due to how they got there. Arabidopsis thaliana‘s originated from central Europe. As it moved to more extreme locations, it would have been the best-adapted plants that survived to pass on genes to their offspring, reducing some diversity. There could also be foundational effects meaning that the plants at the edges were exchanging genes within a limited pool. 

In their article, Estarague and colleagues say, “[T]his study points out the need in functional ecology to go beyond a simple description of functional traits, notably through a better understanding of performance and phenotypic plasticity across environments and evolutionary history.”

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Estarague, A., Vasseur, F., Sartori, K., Bastias, C.C., Cornet, D., Rouan, L., Beurier, G., Exposito-Alonso, M., Herbette, S., Bresson, J., Vile, D. and Violle, C. (2022) “Into the range: a latitudinal gradient or a center-margins differentiation of ecological strategies in Arabidopsis thaliana?,” Annals of Botany, https://doi.org/10.1093/aob/mcab149