Measuring Background Levels of Invertebrate Herbivory in the Arctic Tundra

  • Author / Creator
    Rheubottom, Sarah
  • Climate change will continue to affect the Arctic more intensely than other biomes. These changes can have dramatic effects on biotic interactions that influence the functioning of these systems, including plant-herbivore interactions. Invertebrate herbivores strongly depend on external temperatures for their growth and metabolism and as temperatures in tundra ecosystems increase, increases in the rates of invertebrate herbivory are expected. However, little is known about the current levels of invertebrate herbivory in tundra, and critical information is missing in order to evaluate future changes. This project set out to determine what the baseline level of invertebrate herbivory is, how it varies, and what factors are driving variation across the tundra biome. Utilizing a standardized protocol designed by The Herbivory Network, data was collected from 22 tundra sites during summer 2015. This protocol outlined the methods for leaf collection, so that all data collection was consistent. Data was collected at both the species and community level, as well as at two different spatial scales; sites (0.25-25 km2), and plots within the sites (20x20 m). Leaves were collected from the \"focal species\", defined as the three most common plants species at each plot. Leaves were analysed individually to determine the type of herbivory and the area lost to invertebrate herbivores. At the species level, a total of 45 different focal species were collected. Of those species, four were selected as \"target species\" occurring in ≥6 sites, thus allowing for a comparison across sites; Betula nana, Vaccinium vitis-idaea, Empetrum nigrum and Salix polaris/herbacea. The drivers of invertebrate herbivory were species-specific. E. nigrum showed minimal variation due to its low palatability. Climatic variables such as temperature and precipitation explained some of the variation in herbivory for B. nana and S. polaris/herbacea (temperature only). Latitude and collection date were found to partially drive the variation in B. nana and V. vitis-idaea, although in different directions. Increasing latitudeiiihad a positive effect on B. nana herbivory and later collection date had a negative effect, while V. vitis-idaea showed the opposite. Most of the variation in leaf damage was found within sites, between the different plots, rather than between the individual samples within a plot, suggesting that local characteristics play an important role in determining species level herbivory. At the community level none of the included predictor variables (temperature, precipitation, and collection date) were found to drive the variation in herbivory. Similar for the species level herbivory, most of the variation was driven by unidentified local (within site) characteristics. Overall, invertebrate herbivory was prevalent across the tundra biome, occurred at low intensity, and varied between sites. Both temperature and, in some cases, precipitation were associated with increased levels of herbivory on some of the focal species, and this could result in increased herbivory as climate continues to warm. Climatic variables did not explain the variation in herbivory at the community level, but this could be due to climate having a stronger species-specific effect that was masked by combining species. Further work is required to determine the specific drivers of invertebrate herbivory in order to make more accurate predictions about these impacts on tundra ecosystems in the future.

  • Subjects / Keywords
  • Graduation date
    Spring 2018
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
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