Floral herbivory (florivory) can have direct effects on both female and male reproductive output. Damage to flower parts such as petals and anthers can also have indirect effects by altering floral attractiveness to pollinators. Because carnivorous plants live in nutrient-poor environments and have slow growth rates, florivory may have particularly strong negative effects. However, there has been no study to investigate florivory in carnivorous plants. We conducted a two-year field study on an east-central Texas population of the carnivorous pitcher plant Sarracenia alata and its specialist herbivore Exyra semicrocea. Populations were surveyed for number of flowers attacked, and the mass of floral components was compared between attacked and unattacked flowers.
Results/Conclusions
In 2017, 65% of surveyed flowers were attacked at the end of the flowering season. Based on mass before dehiscence, the mass of anthers after florivory was 49.5% that of unattacked flowers. There were no significant differences between attacked and unattacked flowers in the masses of other floral structures. In 2018, 38% of surveyed flowers were attacked. The mass of attacked ovaries was 50% that of unattacked flowers, the mass of sepals and petals combined was 63% that of unattacked flowers, and the mass of the stigma/style complex was 52% that of unattacked flowers. The mass of attacked anthers before dehiscence was 19% that of unattacked flowers. This study shows that florivory can be substantial in S. alata, and that there was annual variation both in the proportion of flowers attacked in the population and in the extent of damage to floral structures. Future studies should examine the effects of florivory on pollen limitation, pollinator behavior, and recruitment in S. alata.