How do plants react when circumstances change? One method can be to evolve a local adaptation. Another can be be phenotypic plasticity, changing the shape of the plant to tackle a local problem. Silvia Matesanz and colleagues examined the plant Lepidium subulatum, a gypsum specialist to see how it reacts.
Matesanz and colleagues say that plants like L. subulatum are particularly good for investigating how plants adapt. “Plants restricted to gypsum soils, gypsophiles, provide an excellent model to test microevolutionary questions regarding genetic differentiation for functional traits and their plasticity. Because of their high specificity for this substrate, gypsophiles show well-documented adaptations to cope with the strong physicochemical limitations imposed by gypsum, but little is known about how they accommodate other sources of (climatic) environmental variation.
“Gypsum specialists are inherently associated with arid or semi-arid conditions, where water is the most limiting factor. However, widely distributed gypsum endemics may also experience substantial variation in water availability, both fine grained (within sites) and coarse grained (among sites) throughout their range. Despite the pivotal role of this key abiotic factor as a driver of population differentiation and phenotypic evolution in plants, the precise patterns of plastic response to water heterogeneity and whether they vary across populations of gypsum soil specialists remain to be understood.”
To find out how the plants adapted to changing conditions, they collected plants from a number of different climactic environments in Spain. They placed the plants, in two groups, in a common garden, one group got more water than the other. The plants were examined to see if their different origins meant that they reacted to water restriction in different ways. Did different origins give some plants an advantage?
“Despite substantial differences in climatic conditions across their sites of origin, populations of the gypsum specialist L. subulatum expressed broadly similar patterns of functional plasticity,” write the authors. “For most traits, populations showed parallel norms of reaction in response to our contrasting, realistic water availability treatments. Though patterns of plasticity were strikingly similar across populations, there were differences among populations in mean trait values for most traits in both growing seasons. However, these differences were not related to climatic conditions in the populations’ sites of origin. These results suggest that the study populations are composed of highly plastic, general-purpose genotypes, rather than ecotypes adjusted to local climatic conditions, and concur with recent studies showing no evidence of local adaptation in other gypsophiles as well as high functional plasticity to drought.”“These results challenge the notion that habitat specialization may constrain further phenotypic evolution (leading to an evolutionary dead-end), and provide empirical evidence of a commonly evolved plastic response.“