Landscape composition can influence reproductive success of plants in semi-natural grasslands depending on their pollinator dependence

Abstract

In a world where insect pollinator declines are a reality, understanding their effects on the reproduction and persistence of wild plant species is vital to contribute to decisions for appropriate conservation strategies. This is especially true in areas which host a high species diversity, like European semi-natural grasslands. In fragmented habitats in particular, pollinator availability can be influenced by surrounding land use, leading to potential cascading effects of land use on plant reproductive success, which is a key factor in wild plant population dynamics. Here, we assess how the proportion of four land-use types (arable land, forest, leys and permanent grasslands) in the surrounding landscape affects pollinator availability and seed set in semi-natural pastures for three plant species varying in pollinator dependence. We found that landscape composition can be connected to the reproductive output of two pollinator-dependent plant species (Lotus corniculatus and Achillea millefolium), and partly to the availability of their pollinators (bumblebees and flies), while a wind-pollinated species (Plantago lanceolata) was less affected. Furthermore, we found that the relationship between pollinator availability and reproductive success can be non-linear, indicating an optimum beyond which plants can be subjected to over-pollination. Pollinator availability and reproductive success were affected in different ways by land-use depending on the plant species. Our results suggest that maintaining and restoring habitat diversity so that landscapes include structural elements like forests as well as extensive land-use types tied to open land will help to support the persistence of the variety of plants that occur in semi-natural grasslands.