Herbarium specimens reveal long-term decline in pollination services since in the 1970s

Bofeng Song, Heidi Zimmer, Mark Clements, Demetra Rakosy, Tiffany M. Knight, Joanne Bennett

Anthropogenic change has resulted in pollinator decline and altered plant-pollinator interactions. This may drive widespread declines in pollination and reproductive success of plants, yet few datasets allow us to track changes in pollination services over time. Herbaria provide a unique opportunity to assess pollination services across broad spatial and temporal scales, and the associated spatiotemporal anthropogenic change. We quantified changes in pollination services to the orchid genus Caladenia over the past century, a period of rapid land-use intensification and climate change in Australia. Examining 10,494 Caladenia flowers preserved at the Australian National Herbarium showed a reduction in pollination services totaling > 60 % over the whole study period, with rapid declines occurring post 1970. Declines in pollination services occurred across species pollinated by different taxa and threat status. Sexually deceptive species had more pronounced declines in pollinator services. Historical land-use change, and rising temperatures varied by region and were significant predictors of pollination service decline. Our findings provide rare evidence of declines in pollination services modulated by pollination syndrome and demonstrate the value of herbarium collections in understanding global change.