Data: Multigenerational invasive plant exposure causes greater trait shifts belowground than aboveground in a perennial grass

Interactions with plant neighbors can drive trait change over time and across generations through plasticity and selection. Competition from invasive species can influence transgenerational plasticity and result in genetic and morphological changes to offspring of native plants growing in the presence of invasive plants. Invasive species have immensely suppressive impacts, and these effects can be concentrated belowground, though few studies that assess trait change via invasive species interactions consider root traits. Here we use seeds of Sporobolus airoides that grew with and without invasive Russian knapweed (Rhaponticum repens) in field conditions for 58 years on average and were transplanted to a greenhouse. The first generation of seeds from these transplants were collected and or grown for another round of seed collection (generation two). We grew plants from populations with and without invasive exposure\singly in a growth chamber for six weeks. We found trait shifts and trait differences in plant morphology between the groups and observed the largest differences in root traits (e.g., root mass fraction, primary root count, rooting depth). Directionality of trait differences between invasive exposure levels differed by generation; plants were larger in the second generation. These findings indicate that exposure to the invasive plant Russian knapweed led to transgenerational plasticity that had greater influences on root traits, highlighting the importance of considering the maternal environment and roots when evaluating trait changes across generations.