Animal-mediated pollination is a vital ecosystem service to crops and wild plants, and long-term stability of plant–pollinator interactions is therefore crucial for maintaining plant biodiversity and food security. However, it is unknown how the composition of pollinators and the structure of pollinator interactions have changed across longer time spans relevant to examining responses to human activities such as climate change. We resampled an historical dataset of plant–pollinator interactions across several orders of pollinating insects in a subarctic location in Finland that has already experienced substantial climate warming but little land use change. Our results reveal a dramatic turnover in pollinator species and rewiring of plant–pollinator interactions, with only 7% of the interactions shared across time points. The relative abundance of moth and hoverfly pollinators declined between time points, whereas muscoid flies, a group for which little is known regarding conservation status and responses to climate, became more common. Specialist pollinators disproportionately declined, leading to a decrease in network-level specialization, which could have harmful consequences for pollination services. Our results exemplify the changes in plant–pollinator networks that might be expected in other regions as climate change progresses.
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We published a description of the full historical data64 and have made the data openly available on figshare (https://doi.org/10.6084/m9.figshare.c.5828663.v4)65. The subset of historical data and current data used in this work are freely available from GitHub (https://github.com/LeanaZ/Dramatic-plant-pollinator-network-change-across-more-than-a-century-in-the-subarctic). Information on location and accessibility of preserved insect specimens can be requested from the authors. The Biolflor database can be accessed via https://wiki.ufz.de/biolflor/index.jsp.
The R code used for main analyses in this work is available from GitHub (https://github.com/LeanaZ/Dramatic-plant-pollinator-network-change-across-more-than-a-century-in-the-subarctic).
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We thank N. Becker, P. Schnitker and V. Koch for assistance with fieldwork, J. Cobain for help in identifying muscoid flies, J. Kahanpää for expert advice on Diptera taxonomy, J. Pieplow for help in identifying bumblebees and J. Everaars for inputs on historical data curation. We are grateful to V. Stefan for support with statistics and R. Leberger for aiding with visualizations. We also thank colleagues in the spatial interaction ecology group whose comments contributed to the improvement of the manuscript. This research was supported by the Alexander von Humboldt professorship and the Helmholtz Recruitment Initiative, both awarded to T.M.K. and by the support of iDiv by the German Research Foundation (FZT 118).
The authors declare no competing interests.
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a, Location of the study region Kittilä, Lapland, Finland. Kittilä is situated ~120 km north of the Arctic Circle. b, Portrait of Frans F. Silén, who recorded plant–pollinator interactions in Kittilä in the years 1895–1900 (_. F. _qvist, Haparanda. Metsänhoitaja Frans Johan Frithiof Silén (Forester Frans Johan Frithiof Silén). Photo licensed under CC BY 4.0). c, A fly specimen collected by F. Silén in Kittilä; many specimens from his research are stored in the Finnish Museum of Natural History (© L. Zoller). d-e, Photos of the landscape near Kittilä in d, the year 1932 (Mikkola, Erkki. Panoraama Kittilästä: Kumputunturi Jeesiörovan Pohjoislaidalta (Panorama of Kittilä: Kumputunturi from the northern slope of Jeesiörova). Photo licensed under CC BY 4.0) and e, the year 2018 (© L. Zoller). Both photos show the view towards the fell ‘Kumputunturi’. The village of Kittilä lies just outside the photographic frame on the left.
Extended Data Fig. 2 Linear regression of mean vegetation period temperatures over the years 1895–2019.
Black circles indicate annual mean vegetation period temperatures. The relationship was tested using a simple linear model. The red line depicts the regression line and the grey shaded area indicates the 95% confidence interval. Mean vegetation period temperature significantly increased by 1.53 °C across 124 years (two-tailed t-test, no adjustment for multiple comparisons: F1, 123 = 29.78, P > 0 .001, r = 0.1949).
Observations of pollinators are pooled across time periods, for the past observations, conservative numerical estimates were assumed. For better visibility, one species with 917 observations (Thricops) was excluded from the histogram. Only species with >10 observations (22.37% of species) were used in regressions of change in relative abundance and species specialization (d´).
Supplementary Figs. 1–5 and Tables 1–4.
Lists of specialization indices (d´) and change in relative abundance of each species. Numbers are rounded to four digits. Tables are sorted by increasing specialization. Tab one includes the full dataset (all taxa, observations pooled across time periods). Rows printed in bold indicate species with >10 observations. Only these species were used in the regression analyses testing for a dependence of specialization and change in relative abundance (n = 49). Tab two includes four subsets of the data: a, all flies (n = 34); b, bees, wasps and bumblebees (n = 10); c, butterflies and moths (n = 5); and d, hoverflies (n = 27). Only species with >10 observations are included, since only these species were used in the regression analyses testing for a dependence of specialization and change in relative abundance.
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Zoller, L., Bennett, J. & Knight, T.M. Plant–pollinator network change across a century in the subarctic. Nat Ecol Evol 7, 102–112 (2023). https://doi.org/10.1038/s41559-022-01928-3