Temporal synchrony of Silene stellata and its pollinating seed predator, Hadena ectypa, over three years

Background/Question/Methods

Flowering phenology can influence the outcome of interactions. For pollinating seed predators, flowering and pollinator activity are expected to be synchronous to maximize potential positive interactions. For facultative interactions, some plants may be out of synchrony with their pollinating seed predators, resulting in temporally dependent outcomes. The temporal separation between the two key phases of the interaction (pollination and seed predation) could result in variable outcomes for plants flowering early and late in the season. We asked, given the change in pollinating seed predator adult visitation rate across the season, are seed set and predation different for plants that flower early or late in the season? In 2007, we estimated the mid-point of flowering based on field observations and correlated it with predation rate from flowers and fruits collected after senescence. In 2008 and 2009, we closely monitored the timing of flowering and adult moth abundance throughout the season. Plants were visited every 3-5 days, and previously unmarked flowers were marked. The fate of each marked flower was followed in the field until senescence and then processed in the lab to determine seed set, fruit formation rates and flower, fruit and total predation.

Results/Conclusions

Preliminary analyses of plants monitored in 2007 show that flowering date is not predictive of predation rate. This result suggests that predation rate is constant throughout the season. If so, then plants that flower synchronously with adult Hadena activity may enjoy greater pollination success, independent of seed predation rates. In 2008 and 2009, all flowers on 114 and 94 plants, respectively, were marked and followed through senescence and final processing in the lab. Preliminary examination of the 2008 and 2009 flowering and moth visitation datasets reveals three sets of plants – those flowering before, during and after peak Hadena activity. Final analyses will demonstrate the strength of correlation between flowering date and seed set, fruit set, oviposition rates and flower, fruit and seed predation over all plants and within each of the time periods. From these data, we gain an understanding of the timing of flowering and fruit development as related to oviposition and fruit consumption by the moths.