Fecal DNA metabarcoding reveals seasonal and annual variation in willow ptarmigan diet

Abstract

Understanding spatio-temporal variation in the diet of alpineherbivores is important to predict how a changing climate willaffect these species in the future. We examined the spatio-temporal variation in willow ptarmigan (Lagopus l. lagopus)diet using DNA metabarcoding of fecal pellets sampled fromwinter to early summer over three consecutive years.Furthermore, we assessed how snow cover and vegetationphenology affected diet variation. We also investigated sexdifferences in diet composition. We identified 18 importantdiet taxa and the generaBetula, VacciniumandEmpetrumoccurred most frequently. Diet composition and richnessvaried within and between years. Seasonally, there was a shiftfrom a narrow winter diet dominated by trees and dwarfshrubs to a broader spring diet with more nutritious fieldvegetation. This seasonal progression differed among years.The temporal variation in diet was better explained by day ofyear than by snow cover and vegetation phenology. Femaleshad a more diverse diet than males, but there were no sexdifferences in diet composition. Our results demonstrate thatmetabarcoding of fecal samples provides the opportunity toassess factors affecting diet composition of species in alpineecosystems in the context of a changing climate alpine bird,Lagopus lagopus, dietary study,environmental DNA, remote sensing