Data from: Plant-soil interactions during the native and exotic range expansion of an annual plant

Range expansions, whether they are biological invasions or climate
change-mediated range shifts, may have profound ecological and
evolutionary consequences for plant-soil interactions. Range-expanding
plants encounter soil biota with which they have a limited coevolutionary
history, especially when introduced to a new continent. Past studies have
found mixed results on whether plants experience positive or negative soil
feedback interactions in their novel range, and these effects often change
over time. One important theoretical explanation is that plants locally
adapt to the soil pathogens and mutualists in their novel range. We tested
this hypothesis in Dittrichia graveolens, an annual plant that is both
expanding its European native range, initially coinciding with climate
warming, and rapidly invading California, after human introduction. In
parallel greenhouse experiments on both continents, we used plant
genotypes and soils from five locations at the core and edge of each range
to compare plant growth in soil from D. graveolens populations and nearby
control microsites as a measure of plant-soil feedback. Plant-soil
interactions were highly idiosyncratic across sites in each range. On
average, plant-soil feedbacks were more positive in the native range than
in the exotic range. In line with the strongly heterogeneous pattern of
soil responses along our biogeographic gradients, we found no evidence for
evolutionary differentiation between plant genotypes from the core to the
edge of either range. Our results suggest that the evolution of plant-soil
interactions during range expansion may be more strongly driven by local
evolutionary dynamics varying across the range than by large-scale
biogeographic shifts.