Variation in pollen limitation among reproductive modules points to likely resource reallocation in the alpine plant <i>Veratrum grandiflorum</i>

Pollen limitation, a decrease in seed production due to insufficient pollen receipt, may influence plant demography and the evolution of sexual systems. Its empirical estimation of pollen supplementation of some of the flowers on an individual is well known to be prone to overestimation due to potential resource reallocation among the individual's resource pools, from unpollinated flowers and inflorescences. Despite this, studies that evaluate the effect of resource reallocation simultaneously across different modular levels of an individual remain rare, especially in alpine plants. Here, we estimated pollen limitation at three modular levels (i.e., flower, raceme, and whole plant) in the perennial alpine herb Veratrum grandiflorum (Maxim. Ex Baker) Loes in the eastern Himalayan Hengduan Mountains. We used fruit set and seed production as two proxies for female reproductive success. Based on seed production, we found that pollen limitation differed significantly among modular levels, with the highest and lowest values being at the flower and whole‐plant levels, respectively. In contrast, fruit set was relatively insensitive to pollen supplementation, so estimates of pollen limitation were low and did not differ among modular levels. These results point to resource reallocation for seed production among modules within individuals and highlight the importance of multi‐modular and multi‐metric approaches for accurately assessing pollen limitation.