The world is getting warmer and warmer – and many organisms native to lower latitudes or elevations are moving higher.
However, novel organisms moving into a new habitat could disturb the ecological balance which has been established over a long period. Plants and herbivores are characterised by long-term co-evolution, shaping both their geographic distribution and the characteristics that they display in their occupied sites.
At higher elevations, this is seen in insect herbivores being generally less abundant and plants in turn being less well defended against herbivores, as a result of lower energy and shorter growing seasons. In contrast, low-elevation plant species defend themselves against more abundant and diverse herbivores, whether by means of spikes, thorns or hair, or by toxic substances. Climate change could disturb this ecological organisation.
Grasshoppers translocated to high elevations
In an experiment, researchers from ETH Zurich, the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the University of Neuchâtel investigated what could happen if herbivores – in this case various grasshoppers from middle elevations – settled in alpine meadows at higher elevations and encountered new plant communities there. The study has just been published in the journal Science.
The researchers translocated various grasshopper species from medium altitudes (1,400 metres above sea level) to three alpine grassland sites at elevations of 1,800, 2,070 and 2,270 metres above sea level, where the ecologists placed the grasshoppers in cages. The local grasshoppers had previously been removed from the experimental areas. The experiment was carried out in the Anzeindaz region in the Vaud Alps.
In their study, the researchers measured things like how the biomass, structure and composition of the alpine plant communities changed under the influence of the herbivorous insects. The researchers also investigated whether some plant species were more susceptible to herbivory, for instance plants with tougher leaves, or those containing more silica or other constituents such as phenols or tannins.
