Are introduced plants a threat to native pollinator services in montane–alpine environments?

While introduced plants often have restricted distributions at high elevations, their impacts may be more extensive if they compete for native pollinators, potentially reducing pollinatorservices to nativebiotically pollinatedplants. Conversely, introduced biotically pollinatedplants might facilitate improved pollinatorservices to native plantsby supporting higher pollinatordensities and extending the flowering season. We examined weekly pollinatorvisitation to nativeand introduced plants, at five elevations over two flowering seasons on The Remarkables range, south-central South Island, New Zealand. In this area, introduced plants dominate the vegetation at lower elevations but are restricted to disturbed areas above treeline. We tested whether pollinatorvisitation rates and quantities of introduced pollen on insects or transferred to nativeflowers differed with elevation and community context, or with the local abundance of introduced flowers regardless of elevation. Introduced biotically pollinatedplants produced more flowers and flowered later than most nativespecies and were extensively utilised by native solitary bees. Weekly visitation rates to nativeflowers were higher in the first half of the flowering season than the second half, and were positively correlated with visitation rates to co-occurring introduced flowers. Introduced flower abundance did not affect visitation to nativeflowers but did significantly predict the occurrence of introduced pollen on nativeinsects and stigmas of nativeflowers. Pollen contamination was also higher in the latter part of the flowering season. While an increase in introduced flowers at high elevations may benefit native pollinatorsby increasing the quantity and duration of floral resources available, the heavy use of introduced flowers by nativebees will lead to at least localised stigma contamination, particularly for late flowering species. However, more information is required on foraging ranges of native pollinatorsand pollen limitation in nativespecies to understand the consequences of introduced speciesexpansion into alpine areas.