Biotic interactions promote local adaptation to soil in plants - Supplementary data

Although different ecological factors shape adaptative evolution in
natural habitats, we know little about how their interactions impact local
adaptation. Here we used eight generations of experimental evolution with
outcrossing Brassica rapa plants as a model system, in eight treatment
groups that varied in soil type, herbivory (with/without aphids), and
pollination mode (hand- or bumblebee-pollination), to study how biotic
interactions affect local adaptation to soil. First, we show that several
plant traits evolved in response to biotic interactions in a soil-specific
way. Second, using a reciprocal transplant experiment, we demonstrate that
significant local adaptation to soil-type evolved in the “number of open
flowers”, a trait used as a fitness proxy, but only in plants that evolved
with herbivory and bee pollination. Whole genome re-sequencing of
experimental lines revealed that biotic interactions caused a 10-fold
increase in the number of SNPs across the genome with significant allele
frequency change, and that alleles with opposite allele frequency change
in different soil types (antagonistic pleiotropy) were most common in
plants with an evolutionary history of herbivory and bee pollination. Our
results demonstrate that the interaction with mutualists and antagonists
can facilitate local adaptation to soil type through antagonistic
pleiotropy.