Pollen limitation in alpine plants: A meta-analysis

Pollen limitation due to a lack of pollinators has been suggested to be a major factor driving the evolution of floral traits in alpine plants. However, there is a lack of knowledge about the general importance of pollen limitation in the alpine and a general review is needed. We performed a classical and phylogenetic meta-analysis, to assess if alpine plants are in general pollen limited, and if so, if the intensity of pollen limitation differs between alpine and lowland species. We further assessed if pollen limitation of alpine species depends on their reproductive system (inbreeding vs. outcrossing) and if the outcome of PL studies depends on whether supplemental pollination is done at the plant-level or at the partial-level. Our results show that alpine plants are significantly pollen limited. Alpine plants are not significantly more pollen limited than lowland plants. In the alpine, outcrossing species are not significantly more pollen limited than inbreeding species. Moreover, there was no difference in pollen limitation between studies conducted at the plant- vs. partial-level. Our results suggest that pollen limitation in the alpine is not particularly frequent or strong. The lack of resource reallocation processes may be caused by low resource levels in these harsh environments that could be also limiting the plant responses to pollen supplementation experiments.