Data from: Specialization to extremely low-nutrient soils limits the nutritional adaptability of plant lineages

Specialization to extreme selective situations promotes the acquisition of
traits whose coadaptive integration may compromise evolutionary
flexibility and adaptability. We test this idea in the context of the
foliar stoichiometry of plants native to the South African Cape. Whereas
foliar concentrations of nitrogen, phosphorus (P), potassium (K), calcium,
magnesium, and sodium showed strong phylogenetic signal, as did the foliar
ratios of these nutrients to P, the same was not true of the corresponding
soil values. In addition, although foliar traits were often related to
soil values, the coefficients of determination were consistently low.
These results identify foliar stoichiometry as having a strong genetic
component, with variation in foliar nutrient concentrations, especially
[P] and [K], being identified as potentially adaptive. Comparison of
stoichiometric variation across 11 similarly aged clades revealed
consistently low foliar nutrient concentrations in lineages showing
specialization to extremely low-nutrient fynbos heathlands. These lineages
also display lower rates of evolution of these traits as well as a reduced
tendency for foliar [P] to track soil [P]. Reduced evolutionary lability
and adaptability in the nutritional traits of fynbos-specialist lineages
may explain the floristic distinctness of the fynbos flora and implies a
reduced scope for edaphically driven ecological speciation.