QUANTIFYING CONTEXT-DEPENDENT OUTCOMES OF THE INTERACTION BETWEEN <italic>SILENE STELLATA</italic> (CARYOPHYLLACEAE) AND ITS POLLINATING SEED PREDATOR, <italic>HADENA ECTYPA</italic> (NOCTUIDAE), A POTENTIAL MUTUALIST
Kula, Abigail Rogers
Dudash, Michele R
Fenster, Charles B
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Interactions with variable outcomes are particularly useful in allowing for the exploration of ecological conditions that give rise to and allow persistence of mutualistic interactions. Understanding the context and conditions under which outcomes of mutualistic interactions vary is critical to understanding their ecology. Of insect-plant mutualisms, pollination by pollinating seed predators is a unique interaction in which flowers and fruits are food for the pollinator's young, and outcomes range from obligate (e.g., figs-fig wasps) to facultative (e.g., <italic>Silene-Hadena</italic>). The facultative nature of <italic>Silene-Hadena</italic> interactions makes them ideal for a study of the role of ecological conditions in determining interaction outcomes and consequently may inform us of the conditions promoting mutualisms. My goals were to explore variation in the interaction outcome between Silene stellata and its pollinating seed predator, <italic>Hadena ectypa</italic>, under different ecological conditions and, in addition, to understand the role of plant traits in attracting oviposition and the role of oviposition in determining interaction outcomes. My research demonstrates that plants with longer corolla tubes had higher oviposition rates in each year, and I observed significant positive relationships between oviposition and predation and oviposition and fruit initiation. Further, this interaction is antagonistic for spatially isolated plants because low pollination levels of isolated plants resulted in lowered seed set compared with non-isolated plants, and predation was significantly higher for isolated plants. Finally, the magnitude of phenological synchrony between <italic>S. stellata</italic> flowering and <italic>H. ectypa</italic> oviposition and the effect of synchrony on flower and fruit predation varied between seasons. This interannual variability in the effect of synchrony on predation may be attributed to significant differences in within season patterns of flowering and oviposition. My research demonstrates a link between oviposition and host plant traits, the role of oviposition in host plant reproduction and the identification of two ecological scenarios under which the interaction outcomes between <italic>S. stellata</italic> and <italic>H. ectypa</italic> vary. This variation under different ecological scenarios, along with positive relationships between oviposition and both predation and fruit initiation, demonstrates a mechanism for the persistence of this interaction and other facultative pollinating seed predator interactions.