Saltmarsh on the Atlantic and Gulf Coast is a species poor system with high primary productivity. In Georgia saltmarsh, Spartina alterniflora is the dominant grass species and Orchelimum fidicinium is the dominant chewing insect that consumes S.alterniflora leaves, flowers, and small leafhoppers. The abundance of O.fidicinium fluctuates greatly inter-annually. Yet it is unclear whether this fluctuation is driven by climatic factors or food availability. It is also unclear whether their presence in the saltmarsh will have significant influence on S.alterniflora. We used regression models to examine 13 years of environmental and biotic data collected from four Georgia LTER saltmarsh sites to determine factors that may influence O.fidicinium abundance and the consequences of O.fidicinium presence. Then we constructed a simple path analysis model to highlight significant results.
Results/Conclusions
Based on forward step-wise regression model, previous year’s mean annual temperature negatively influenced O.fidicinium abundances. Other predictors used were precipitation, river discharge, plant biomass, number of flowers, and leafhopper presence, but none of them significantly predicted O.fidicinium abundance. To examine the consequence of O.fidicinium on S.alterniflora, we used a linear regression model and found significant negative relationships between O.fidicinium abundance and both the number of S.alterniflora flowers and biomass. Overall, our results indicate that O.fidicinium population is strongly influenced by previous year’s air temperature, where higher mean temperature one year would lead to decreased O.fidicinium abundance next year. Although the importance of O.fidicinium was previously underappreciated, here we demonstrate the presence of these katydids can have significant influence on both the sexual reproduction (flower) and growth (leaves) of S.alterniflora.