MEPS 487:41-54 (2013)  -  DOI: https://doi.org/10.3354/meps10349

ABSTRACT: Consumers can be important in controlling the abundance and composition of plants in salt marsh communities. In particular, the marsh periwinkle Littoraria irrorata is a common inhabitant of lower latitudinal salt marshes that can cause significant losses of plant (Spartina alterniflora) biomass. Research to date has focused on Littoraria effects on Spartina vegetative biomass, and we have little understanding of whether or how this plant–consumer interaction influences Spartina reproductive success. Surveys of natural marshes across the NE Gulf of Mexico highlighted the importance of this knowledge gap, as we observed more Littoraria climbing on reproductive Spartina compared with vegetative stems. With a series of experiments, we showed that this preference for reproductive stems is based on plant morphology: reproductive stems are taller and more rigid than vegetative stems, and snails preferentially climb on plants with these characteristics. This plant host preference is likely due to refuge value based on stem structure, and not due to variation in food quality. Despite this preference, we found no evidence that this aggregation of snails negatively impacts Spartina short-term reproductive success in a field experiment. Instead, we observed a trend towards increased Spartina reproductive output in the presence of snails. Thus, Spartina may mitigate the negative impact of snail presence on vegetative biomass by increasing allocation to sexual reproduction. Our results highlight the importance of considering each stage of a plant’s life history when evaluating the relative importance of plant–consumer interactions.

KEY WORDS: Herbivory · Littoraria irrorata · Plant–consumer interactions · Salt marsh · Seed predation · Spartina alterniflora