Wed, Aug 04, 2021:On Demand
Background/Question/Methods
The effects of pollination on plant demographic vital rates other than reproduction are largely unknown, which limits our ability to predict how changes in pollination may affect plant population growth rates. This knowledge gap is especially relevant in light of declining pollinator populations and a growing need to understand their ecological consequences. Pollinator-mediated changes in seed production are unlikely to have straightforward effects on plant population growth rates, especially in iteroparous perennials where costs of reproduction and resource reallocation are common. The first step toward understanding the consequences of altered pollination on plant population growth is to assess the effects of pollination on vital rates beyond reproduction, namely, survival and growth. Therefore, we examined how multiple demographic vital rates responded to three treatments: reduced pollination, increased pollination, and an unmanipulated control in three long-lived perennial plant species: Delphinium nuttallianum, Hydrophyllum fendleri, and Potentilla pulcherrima, at the Rocky Mountain Biological Laboratory in Colorado, USA. We bagged 50% of flowers to reduce pollination and added supplemental outcross pollen to stigmas to increase pollination. We measured survival, vegetative growth, flowering, and seed production on tagged individuals across the three treatments in 2018, 2019, and 2020.
Results/Conclusions Pollination treatments consistently affected seed production across all three species. In particular, plants in the reduced treatment produced fewer seeds than controls for all three species in most years. However, pollen limitation was only evident in some species and in a subset of years. Pollination treatments affected the probability of flowering in the following year in two species, D. nuttallianum and P. pulcherrima. Plants with reduced pollination were more likely to flower in the following year, suggesting that plants reallocate resources to future reproduction when they receive low pollination. Pollination treatments also affected size in the following year in two species, H. fendleri and P. pulcherrima. Plants with reduced pollination were larger in the following year (but only compared to supplemented plants in one species). Thus, there is some evidence that plants may reallocate resources to growth when they receive low pollination. Pollination treatments only affected survival in one species, P. pulcherrima, where plants with reduced pollination were more likely to survive to the following year. In summary, altered pollination levels can affect vital rates other than reproductive output in the present year, which is especially important when considering potential effects of pollination on plant population growth rates.
Results/Conclusions Pollination treatments consistently affected seed production across all three species. In particular, plants in the reduced treatment produced fewer seeds than controls for all three species in most years. However, pollen limitation was only evident in some species and in a subset of years. Pollination treatments affected the probability of flowering in the following year in two species, D. nuttallianum and P. pulcherrima. Plants with reduced pollination were more likely to flower in the following year, suggesting that plants reallocate resources to future reproduction when they receive low pollination. Pollination treatments also affected size in the following year in two species, H. fendleri and P. pulcherrima. Plants with reduced pollination were larger in the following year (but only compared to supplemented plants in one species). Thus, there is some evidence that plants may reallocate resources to growth when they receive low pollination. Pollination treatments only affected survival in one species, P. pulcherrima, where plants with reduced pollination were more likely to survive to the following year. In summary, altered pollination levels can affect vital rates other than reproductive output in the present year, which is especially important when considering potential effects of pollination on plant population growth rates.