Two hundred years of changes in orchid pollination revealed using herbarium specimens

Abstract

Orchids are one of the most diverse plant families and are renowned for their highly specialised interactions with pollinators. Despite growing evidence of orchid population decline, pollinator decline and rising concerns for orchid reproductive success, long-term changes remain poorly understood. To address this gap, we analysed changes in pollinarium removal, as a proxy for pollination success, in herbarium specimens of three species-rich orchid genera (Disa, Oncidium and Ophrys) hosted at the Royal Botanic Gardens, Kew, which has a rich and diverse orchid collection spanning the past two centuries. The selected genera occur in different major regions (subtropical and tropical Africa, predominantly temperate Europe, and tropical America, respectively). Our analysis reveals that pollinarium removal declined significantly in Disa and Oncidium, particularly among species with deceptive strategies or specialised pollination mechanisms. In contrast, Ophrys showed a significant increase, driven by Apidae-pollinated species, whereas pollinarium removal for Andrenidae-pollinated species declined over time. These contrasting findings reflect the role of orchid identity, pollinator availability and pollination strategy in shaping reproductive success under anthropogenic change. Overall, this study demonstrates the power of herbarium specimens to reveal long-term ecological changes, providing unique insights into the response of specific plant-pollinator interactions to increasing anthropogenic pressure.