Reproductive compensation of a perennial plant Sanguisorba tenuifolia to herbivory by Phengaris teleius

Plants that are consumed by herbivores incur a reduction in fitness. Therefore, plants need to prepare to defend against and/or avoid herbivory using ‘resistance’ and/or ‘tolerance’ systems. Phengaris teleius is a specialist herbivore of Sanguisorba tenuifolia. Phengaris teleius lays eggs in the flower buds of S. tenuifolia and the larvae of P. teleius feed on the ovaries and ovules of S. tenuifolia. In order to clarify the extent of herbivory damage by P. teleius and effect on reproduction in S. tenuifolia, we conducted field observations and artificial cutting experiments carried out in the natural habitat where both P. teleius and S. tenuifolia live sympatrically. Phengaris teleius often lays one egg per spike, and about half of the total eggs were laid on the spike that developed at the shoot apex and was largest in size. The fruits were damaged most heavily in the spike in which an egg was laid. However, the number of fruits was almost the same between individuals with no damage and individuals with a feeding damage rate of 40% or less. This showed that compensation would be achieved by increasing the number of fruits in other spikes without damage. On the other hand, because no compensation was detected in the cutting experiments, it was considered that compensation may be induced by biological stimuli produced by P. teleius. These responses may be one of the mechanisms for continuing the interspecific relationship between S. tenuifolia (host plant) and P. teleius (herbivore insect).