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| September 2007 |
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Climate change gives invasive species the edge over their indigenous counterpartsEngela Duvenhage
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Springtail. Image Brent Sinclair |
Research on the springtails of sub-Antarctic Marion Island, conducted by scientists from Stellenbosch University and from Norway, shows that interactions between climate change and invasive species pose a major challenge to biodiversity, and therefore to human welfare.
In a paper in the latest edition of the Proceedings of the Royal Society B: Biological Sciences titled "Phenotypic plasticity mediates climate change responses among invasive and indigenous arthropods", the scientists investigated the synergies between the effects of climate change and invasion.
These have long been thought to pose a major potential challenge to biodiversity.
"Empirical evidence for such synergy has been lacking," says lead author Prof Steven Chown, director of the DST-NRF Centre of Excellence for Invasion Biology (CIB) based at Stellenbosch University, "but our research has now shown how climate change benefits invasive species because of the way in which they respond to the environment."
"In essence, invasives like it hot, whilst indigenous species like it cold," he said, summarizing the study.
He was joined in the research by CIB colleagues Dr Sarette Slabber, Prof Melodie McGeoch and Charlene Janion, as well as Prof. Hans Petter Leinaas of the University of Oslo in Norway.
They showed that in a temperate terrestrial ecosystem, invasive and indigenous springtail species differ in the form of their phenotypic plasticity such that warmer conditions promote survival of dry conditions in the invasive species and reduce it in the indigenous ones. 'Phenotypic plasticity' is the ability of individuals to modify their behaviour, morphology or physiology in response to altered environmental conditions.
Significant declines were seen in the densities of indigenous species and little change in those of invasive species in a manipulative field experiment on Marion Island that mimicked climate change trends.
Marion Island has a cool, wet, windy climate that has shown substantial change over the past 50 years, including an increase in mean annual temperature of more than 1°C and a decline in precipitation of more than 500 mm per annum. In other words, it is showing global change-type drought.
The island is home to 16 springtail species. Five of these are invasive and thought to have been introduced following the establishment of the South African scientific station on the island in 1947. Samples of the six most commonly found species were subjected to controlled laboratory experiments as well as field experiments to test the impact that various temperature and precipitation levels had on their ability to survive.
"We suggest that it is not so much the extent of phenotypic plasticity that distinguishes climate change responses among these invasive and indigenous species, as the form that this plasticity takes," Prof Chown says.
"Nonetheless, this differential physiological response provides support for the idea that in temperate terrestrial systems experiencing global change-type drought, invasive species may well be at an advantage relative to their indigenous counterparts."
"Also, the density of indigenous species declined dramatically when exposed
to dry conditions, while invasive species density was unaffected in field. The
laboratory and field work nicely match to show that climate change will benefit
invasive species at the expense of their indigenous counterparts."
More information:
Prof Steven
Chown, Director: DST-NRF Centre of Excellence for Invasion Biology,
University of Stellenbosch
Email slchown@sun.ac.za
Website www.sun.ac.za/cib
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