This study was based on exploiting data from the European EXAMINE consortium, which was inaugurated in 1968.  Some INRA members of this network chose eight of its sites for this project in western Europe: four sites in France (Rennes, Colmar, Arras and Montpellier), three sites in England and one in Scotland.  These trapping sites represented contrasting biological and geographical situations, and have been functioning for a long time: between 28 and 38 years.  It was this continuous observation of aphid populations over several decades which allowed the INRA scientists to obtain their results.

An increase in biodiversity: +20% species in 30 years

At the eight study sites, a total of 392 aphid species were identified, the mean number of species per site being 212.  These numbers had increased very markedly over the past 40 years: an average of one species per year and per site, or approximately 8 species more for each additional degree Celsius.
Some species were common to all sites, while others, on the contrary, exhibited a more limited distribution.  Some species were observed on a regular basis, while others were only seen during certain years.  Of these, some species were present at the beginning of the network but absent at the end of the observation period (although they could not be qualified as extinct); by contrast, others appeared during the period and were then observed regularly, and finally some species were only observed episodically.
Years with particularly high or low temperatures generally corresponded to a larger or smaller number of species, respectively.  Some of these species were abundant, others rare.  While the number of abundant species proved stable over 25 years, annual variations in the total number of species concerned rare species.  Thus an increase in temperature probably favoured the development of newly-introduced species and stimulated species which had previously been rare and then reached detectable levels.

The second major impact of warming concerns the date of the first spring aphid migrations.  For example, at the English site of Rothamsted, this date was around May 24 in the 1960s, and is currently around May 7, or nearly three weeks earlier than 40 years ago.
At practically all the EXAMINE network sites, advancement of the first migration varied as a function of species and site from one day every 5 years to more than three days per year, or from 1 to 10 weeks over the past 40 years.

Trap situated at the INRA Research Centre.  Traps can aspirate all insects at an altitude of 12 m.  The insects are harvested at regular intervals and then identified one by one.  The traps function throughout the year.

The EXAMINE database still contains an enormous fund of information.  It should make it possible to detect changes to the geographical distribution of species (shift towards the north) and to link their different types of response to warming with their biological traits.  It will also be important to consider these specific results in the context of current scientific debate about the functioning of biosystems and the distribution of biodiversity.

¹ Partners:
The EXAMINE consortium (http://www.rothamsted.bbsrc.ac.uk/examine/), Rothamsted Research, Institut Français de la Biodiversité, Agroclim, Météo France

References:
Cocu N., Harrington R., Rounsevell M., Worner S.P., Hullé M., 2005: Geographical location, climate and land use influences on the phenology and numbers of the aphid, Myzus persicae, in Europe. Journal of Biogeography 32, 615-632
Cocu N., Rounsevell M.D.A., Harrington R., Pearson R.G., Hullé M., The response of the aphid Myzus persicae to scenarios of climate and land use change. Global Change Biology (in press)
Harrington, R. Clark, S.J., Welham, S.J., Verrier, P.J., Denholm, C.H., Hullé, M., Maurice, D., Rounsevell, M.D.A., Cocu, N. and EU EXAMINE Consortium. Environmental change and the phenology of European aphids. Global Change Biology (in press)