Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA.
Rocky Mountain Biological Laboratory, Crested Butte, CO, USA.
Am J Bot. 2020 Mar;107(3):445-455. doi: 10.1002/ajb2.1439. Epub 2020 Feb 21.
Flowering time may influence pollination success and seed set through a variety of mechanisms, including seasonal changes in total pollinator visitation or the composition and effectiveness of pollinator visitors.
We investigated mechanisms by which changes in flowering phenology influence pollination and reproductive success of Mertensia ciliata (Boraginaceae). We manipulated flowering onset of potted plants and assessed the frequency and composition of pollinator visitors, as well as seed set. We tested whether floral visitors differed in their effectiveness as pollinators by measuring pollen receipt and seed set resulting from single visits to virgin flowers.
Despite a five-fold decrease in pollinator visitation over four weeks, we detected no significant difference in seed set among plants blooming at different times. On a per-visit basis, each bumblebee transferred more conspecific pollen than did a solitary bee or a fly. The proportion of visits by bumblebees increased over the season, countering the decrease in visitation rate so that flowering time had little net effect on seed set.
This work illustrates the need to consider pollinator effectiveness, along with changes in pollinator visitation and species composition to understand the mechanisms by which phenology affects levels of pollination.
开花时间可能通过多种机制影响传粉成功和结实率，包括传粉者总访问量或传粉者访客组成和有效性的季节性变化。
我们研究了开花物候变化如何影响 Mertensia ciliata（紫草科）的传粉和生殖成功。我们操纵盆栽植物的开花起始时间，并评估传粉者访客的频率和组成，以及结实率。我们通过测量处女花单次访问的花粉接收和结实率来测试花访客在作为传粉者方面的有效性是否存在差异。
尽管在四周内传粉者访问量减少了五倍，但我们在不同时间开花的植物之间没有发现结实率有显著差异。在单次访问的基础上，每只熊蜂传递的同种花粉比单独的蜜蜂或苍蝇多。随着季节的推移，熊蜂的访问比例增加，抵消了访问率的下降，因此开花时间对结实率的净影响很小。
这项工作说明了需要考虑传粉者的有效性，以及传粉者访问和物种组成的变化，以了解物候如何影响授粉水平的机制。
