Data from: Environmental stress and resource availability affect the maintenance of genetic variation in a dominant marsh plant (Spartina alterniflora)

Changes in genetic variation, and particularly documented declines in
genetic diversity, influence not only evolutionary potential but also
current ecological function. Given this context, it is essential to
understand what abiotic and biotic factors promote or disrupt the
maintenance of genetic variation in natural populations. To address this
knowledge gap in the context of salt marsh plants, we established a 3-year
field experiment testing the independent and interactive effects of
nutrient availability and physical stress on the maintenance of plant
(Spartina alterniflora) genotypic diversity. We found that in environments
with high physical stress (i.e., low marsh elevations), diversity declined
over time. However, the addition of nutrients promoted the maintenance of
Spartina genotypic diversity across the physical stress gradient. We also
observed changes in genotypic composition and genetic divergence across
environmental stress treatments, indicating variation among Spartina
genotypes in their response to these factors. Our results suggest that
tidal inundation acts a selective gradient within coastal marshes,
altering genotypic diversity and composition across the landscape.
Moreover, our work highlights that the effects of increasing inundation
due to continued sea level rise on the maintenance of diversity may be
modulated by concomitant changes in nutrient inputs, with cascading
effects on marsh structure and function.