Herbivory and ramet performance in the clonal herb Trientalis europaea L.

Abstract

1 The intensity of leaf damage caused by invertebrate herbivores and grazing by vertebrates and their effects on clonal growth, survival and reproduction were examined in a population of the forest herb Trientalis europaea during 4 years. 2 Levels of herbivory were low and varied between years in the studied population. Larger ramets were exposed to a greater risk of both grazing and leaf defoliation. Ramets that suffered leaf damage in 1 year experienced an increased probability of leaf damage in succeeding years. The probability of suffering herbivore attack was independent among the ramets belonging to the same clonal fragment, suggesting that clonal propagation might operate as a risk‐spreading strategy in this species. 3 Leaf damage did not affect any measure of plant performance, probably due to the low amounts of leaf area removed by invertebrate herbivores. In contrast, vertebrate grazing affected all phases of the pseudo‐annual life cycle of T. europaea. Grazing prevented flowering and fruiting, increased ramet mortality during summer and decreased tuber production. Furthermore, grazed ramets produced shorter stolons and smaller tubers, which in turn had a lower winter survival and produced smaller ramets in the following growing season. The large impact of grazing was due to the consumption of the whole of the single shoot of ramets of T. europaea. Although regrowth was possible, secondary shoots were significantly smaller and assimilation was delayed. 4 Tubers originating from grazed ramets were placed shallower than tubers from ungrazed ramets. This could be due to an alteration in the growth pattern of stolons of the grazed ramets.