In short-lived monocarpic perennials flowering probability depends on size and relative growth. Reproducing at a smaller size results in a higher prereproductive survival and shorter generation time but also may lead to lower fecundity. Conversely, reproducing at a larger size allows greater fecundity but leads to higher mortality during the prolonged vegetative period. Herbivory may influence the above described relationships via alterations in size at reproduction and survival. Here we use field data to explore in detail the reproduction of the short-lived monocarpic perennial C. vulgare under seasonal grazing. Vegetative plants were marked in paddocks with and without winter grazing, and their size, growth, and flowering status were recorded during a growing season in a field grazing experiment. Grazing increased both survival of vegetative plants and flowering probability, but it did not affect flowering size. The increase in flowering probability is a result of differential plant growth and size and may be related to greater resource availability, including light (necessary for flowering induction in C. vulgare) in grazed paddocks. 1. Introduction Biennial plants have been characterised as plants that grow vegetatively in their first growing season, flower in the next, and die after flowering. However, in the field, most of them behave as short-lived monocarpic perennials [1–3]. In these species, flowering probability depends on size and relative growth just before bolting rather than on age [2, 4]. In relation to this trait, the concepts of “flowering size,” “size at flowering,” and “threshold size for flowering” have been used equivalently. The threshold size for flowering is equal to or above the physiological minimum size to produce one seed, and it is referred to as an internal plant setting that can be reflected by plant size at flowering [5]. Optimisation models for flowering have shown that the threshold size is probably the result of the interplay between size-dependent growth, which in turn determines the increase in seed production and size-dependent survival [1, 5, 6]. The optimal reproductive size is determined through the trade-off between survival and fecundity affected by the critical size of reproduction. Reproducing at a smaller size results in a higher prereproductive survival and shorter generation time but also may lead to lower fecundity. Conversely, reproducing at a larger size allows greater fecundity but leads to higher mortality during the prolonged vegetative period [7]. In real populations, factors like pollination
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