Data for: Interactions between environmental factors drive selection on cyanogenesis in Trifolium repens

Phenotypic and genetic clines frequently evolve due to varying selection
along environmental gradients. However, the specific environmental factors
that impose differential selection are often multivariate and difficult to
tease apart. We addressed this complexity using a factorial manipulation
of watering, soil nutrients, and (simulated) herbivory in controlled
conditions to better understand the agents of selection driving the
evolution of clines in a polymorphic chemical antiherbivore defence,
hydrogen cyanide (HCN), of the plant white clover (Trifolium repens L.).
We found the presence or absence of the two metabolic components required
for HCN production (cyanogenic glucosides and linamarase) to be more
prominent determinants of vegetative growth and sexual reproduction in T.
repens than HCN itself. We also found that the ability to produce one or
both of cyanogenic glucosides or linamarase resulted in a growth advantage
under drought and simulated herbivory that outweighs the metabolic cost of
their production. These results support the view that the metabolic
components underlying HCN play important roles beyond defence by
increasing plant tolerance to stress. The growth advantage under drought,
however, was diminished in the absence of nutrient addition, consistent
with multivariate interactions as drivers of selection. This study
provides novel insight into how a cosmopolitan plant has adapted to
environmental gradients, and more generally, highlights the importance of
considering interactions between multiple environmental factors when
studying the evolution of phenotypic and genetic clines.