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Productivity and related soil properties mediate the population‐level consequences of rodent seed predation on Blanketflower, Gaillardia aristata

Hegstad, Ryan J., Maron, John L.
Thejournal of ecology 2019 v.107 no.1 pp. 34-44
Gaillardia aristata, Peromyscus maniculatus, demography, environmental factors, fecundity, forbs, grasslands, indigenous species, mice, perennials, plant communities, seed predation, seeds, soil nutrients, soil properties, species recruitment, Montana
Plants are frequently attacked by consumers that reduce seed numbers. However, our ability to predict whether seed loss results in parallel changes in future recruitment or plant abundance remains poor. Progress in this area requires simultaneously understanding: (1) how spatial variation in environmental conditions influence recruitment and other demographic rates, and (2) how the magnitude of seed loss varies spatially and relative to seed limitation. We experimentally assessed how postdispersal seed predation by deer mice (Peromyscus maniculatus) influenced recruitment of the native perennial forb, Gaillardia aristata, in western Montana (USA) grasslands. To explore whether seed limitation and the population‐level consequences of seed predation varied predictably based on environmental conditions, we added seeds to plots where mice had access or were excluded at sites occurring over a strong gradient of soil characteristics and plant community productivity. We also quantified whether components of Gaillardia demography varied in ways that may compensate for or exacerbate the population‐level effects of seed predation across this environmental gradient. Across two replicate years, recruitment was highest at low productivity/soil nutrient sites and decreased towards the opposite end of the gradient. Postdispersal seed predation strongly reduced Gaillardia recruitment in both years, and the impacts of seed predation on recruitment were greater at sites with lower productivity and fewer soil nutrients and decreased towards the opposite end of the gradient. Growth and fecundity varied among populations in ways that could buffer Gaillardia populations from stronger effects of seed predation, whereas survival varied among populations in a way that may intensify these effects. Synthesis. Together, these results show that postdispersal seed predation can importantly limit plant recruitment and that the magnitude of these effects were predicted by variation in underlying environmental conditions that influence recruitment and other key demographic rates.