How shrub encroachment under climate change could threaten pollination services for alpine wildflowers: A case study using the alpine skypilot, Polemonium viscosum. Issue 17 (28th July 2017)

• Record Type: Journal Article
• Authors: Kettenbach, Jessica A.; Miller‐Struttmann, Nicole; Moffett, Zoë; Galen, Candace
• Is Part Of: Ecology and evolution. Volume 7:Issue 17(2017:Sep.)
• Page Start: 6963
• Page End: 6971
• Publication Date: 2017-07-28
• Subjects: climate change -- heterospecific pollen transfer -- plant–climate interactions -- Polemonium viscosum -- reproductive ecology -- Salix -- selection on floral traits -- shrub encroachment; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.3272
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Under climate change, shrubs encroaching into high altitude plant communities disrupt ecosystem processes. Yet effects of encroachment on pollination mutualisms are poorly understood. Here, we probe potential fitness impacts of interference from encroaching Salix (willows) on pollination quality of the alpine skypilot, Polemonium viscosum . Overlap in flowering time of Salix and Polemonium is a precondition for interference and was surveyed in four extant and 25 historic contact zones. Pollinator sharing was ascertained from observations of willow pollen on bumble bees visiting Polemonium flowers and on Polemonium pistils. We probed fitness effects of pollinator sharing by measuring the correlation between Salix pollen contamination and seed set in naturally pollinated Polemonium . To ascertain whether Salix interference occurred during or after pollination, we compared seed set under natural pollination, conspecific pollen addition, and Salix pollen addition. In current and past contact zones Polemonium and Salix overlapped in flowering time. After accounting for variance in flowering date due to latitude, Salix and Polemonium showed similar advances in flowering under warmer summers. This trend supports the idea that sensitivity to temperature promotes reproductive synchrony in both species. Salix pollen is carried by bumble bees when visiting Polemonium flowers and accounts for up to 25% of the grains on Polemonium pistils. Salix contamination correlates with reduced seed set in nature and when applied experimentally. Postpollination processes likely mediate these deleterious effects as seed set in nature was not limited by pollen delivery. Synthesis: As willows move higher with climate change, we predict that they will drive postpollination interference, reducing the fitness benefits of pollinator visitation for Polemonium and selecting for traits that reduce pollinator sharing. Abstract : Indirect effects of Salix shrub encroachment into high‐altitude ecosystems have reduced the quality of pollination with fitness consequences in reduced seed set of a native wildflower, Polemonium viscosum . We predict that as encroachment continues with climate change, the range of P. viscosum populations impacted by pollination interference from Salix shrubs will increase concomitantly.