Terrestrial macro-arthropods of the sub-Antarctic islands of Possession (Crozet Archipelago) and Kerguelen: inventory of native and non-native species

International audienceThe sub-Antarctic islands of the Southern Ocean harbor biogeographically peculiar biotas which are under threat from climate change, biological invasions and their interactions. Understanding both the indigenous and changing non-indigenous components of these islands is essential for the conservation and management of their biotas. Based on several years of systematic sampling, we present an updated list of terrestrial, free-living macro-invertebrates (insects and spiders) present on the islands of Possession (Crozet Archipelago) and Kerguelen. Ninety-four species were recorded in total on both islands. Forty-one are strictly endemic to one of the two islands, 16 are endemic to the South Indian Ocean Province, and only three were recorded on other sub-Antarctic islands. Beetles and more particularly weevils are the most characteristic group of the fauna of these islands: they include 35 species of which 89% are native and 66% are endemic. One third of the species (30 of 94) are non-indigenous species now naturalized. We discuss these results in terms of biogeography, ecological disharmony and impact of biological invasions

Les pucerons, indicateurs de changements globaux ?

National audienc

Timing of dispersal: effect of ants on aphids

International audienceMutualists can affect many life history traits of their partners, but it is unclear how this translates into population dynamics of the latter. Ant-aphid associations are ideal for studying this question, as ants affect aphids, both positively (e.g., protection against natural enemies) and negatively (e.g., reduction of potential growth rates). The unresolved question is whether these effects, which have been observed at the level of individuals and under controlled environmental conditions, have consequences at the population level. On estimating aerial aphid populations by using weekly suction trap data spanning up to 22 years from different locations in France, we show that in ant-attended aphid species long-distance dispersal occurs significantly later, but that the year-to-year changes in the peak number of migrants are not significantly lower than for non-attended aphids. Host alternation had the same retarding effect on dispersal as ant attendance. We discuss the delay in the timing of dispersal in ant-attended aphids, and potential costs that arise in mutualistic systems

Is the life cycle of high arctic aphids adapted to climate change?

International audienceThe high arctic aphid Acyrthosiphon svalbardicum Heikinheimo is endemic to Svalbard and has developed a shortened life cycle to cope with harsh environmental conditions prevailing in this archipelago. Previous studies in the 1990s showed that contrarily to Sitobion calvulum, a species which is also restricted to Svalbard and displays a two-generation life cycle, A. svalbardicum can produce a third generation that, on average, should complete its development and reproduction once every 28 years. Because temperature has risen substantially in Svalbard during the past 10 –15 years and is predicted to rise further, budget requirements for this extra-generation should be met more and more frequently and the impact of the resulting demographic increase should be easily measurable in field populations of A. svalbardicum. Here, we tested this hypothesis by performing a series of experiments designed to study population dynamics and morph production of A. svalbardicum. Surprisingly, the three-generation life cycle was not detected either in field populations surveyed for two consecutive years or in controlled conditions where temperature was manipulated. Although we cannot reject the possibility that A. svalbardicum populations may develop a three-generation life cycle under certain circumstances, this strategy seems very rare and not adaptive as it would have been selected in the recent years of warming observed in Svalbard

Monitoring and Forecasting

International audienc

First report of Nasturtium as a natural host of Cherry leaf roll virus on Amsterdam island

International audienc

Vulnerability of native communities to invasive insects and climate change in sub-Antarctic islands.

communication oral

Spatial autocorrelation as a tool for identifying the geographical patterns of aphid annual abundance

International audience1 A spatial autocorrelation analysis was undertaken to investigate the spatial structure of annual abundance for the pest aphid Myzus persicae collected in suction traps distributed across north-west Europe.2 The analysis was applied at two different scales. The Moran index was used to estimate the degree of spatial autocorrelation at all sites within the study area (global level). The contributions of each site to the global index were identified by the use of a local indicator of spatial autocorrelation (LISA). A hierarchical cluster analysis was undertaken to highlight differences between groups of resulting correlograms.3 Similarity between traps was shown to occur over large geographical distances, suggesting an impact of phenomena such as climatic gradients or land use types.4 The presence of outliers and zones of similarity (hot-spots) and of dissimilarity (cold-spots) were identified indicating a strong impact of local effects.5 Several groups of traps characterized by similarities in their local spatial structure (correlograms, value of Moran's I-i) also had similar values for land use variables (the area occupied by agricultural zones, forest and sea).6 It is concluded that trap data can provide information about Myzus persicae that is representative of large geographical areas. Thus, trap data can be used to estimate the aerial abundance of this species, even if the suction traps are not regularly and densely distributed

Etude de la prévalence et de la diversité moléculaire du<em> Barley yellow dwarf virus</em> dans les îles sub-Antarctiques Kerguelen

National audienc

Les pucerons des grandes cultures : Cycles biologiques et activités de vol

National audienc