Aphid–willow interactions in a high Arctic ecosystem: responses to raised temperature and goose disturbance |
| |
Authors: | Mark A. K. Gillespie Ingibjörg S. Jónsdóttir Ian D. Hodkinson Elisabeth J. Cooper |
| |
Affiliation: | 1. Institute of Integrative and Comparative Biology, University of Leeds, , Leeds, LS2 9JT UK;2. University Centre in Svalbard (UNIS), , Longyarbyen, N‐ 9171 Norway;3. Institute of Biology, University of Iceland, , Reykjavik, IS‐101 Iceland;4. School of Natural Sciences & Psychology, Liverpool John Moores University, , Liverpool, L3 3AF UK;5. Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, University of Troms?, , Troms?, N‐9037 Norway |
| |
Abstract: | Recently, there have been several studies using open top chambers (OTCs) or cloches to examine the response of Arctic plant communities to artificially elevated temperatures. Few, however, have investigated multitrophic systems, or the effects of both temperature and vertebrate grazing treatments on invertebrates. This study investigated trophic interactions between an herbivorous insect (Sitobion calvulum, Aphididae), a woody perennial host plant (Salix polaris) and a selective vertebrate grazer (barnacle geese, Branta leucopsis). In a factorial experiment, the responses of the insect and its host to elevated temperatures using open top chambers (OTCs) and to three levels of goose grazing pressure were assessed over two summer growing seasons (2004 and 2005). OTCs significantly enhanced the leaf phenology of Salix in both years and there was a significant OTC by goose presence interaction in 2004. Salix leaf number was unaffected by treatments in both years, but OTCs increased leaf size and mass in 2005. Salix reproduction and the phenology of flowers were unaffected by both treatments. Aphid densities were increased by OTCs but unaffected by goose presence in both years. While goose presence had little effect on aphid density or host plant phenology in this system, the OTC effects provide interesting insights into the possibility of phenological synchrony disruption. The advanced phenology of Salix effectively lengthens the growing season for the plant, but despite a close association with leaf maturity, the population dynamics of the aphid appeared to lack a similar phenological response, except for the increased population observed. |
| |
Keywords: | climate change grazing herbivory phenology
Salix polaris
Sitobion calvulum
Svalbard trophic mismatch |
|
|