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Abstract: The high arctic Svalbard archipelago is characterized by a low insect species richness explained by both extreme living conditions and insularity. Here, we described two new species of Hymenopteran parasitoids found in Spitsbergen, the main island of Svalbard, using aphids as hosts. We named the first one Diaeretellus svalbardicum (Hymenoptera: Braconidae) because of morphological similarities with other European members of the Diaeretellus genus. D. svalbardicum parasitizes exclusively the aphid Acyrthosiphon svalbardicum, a species endemic to Svalbard. We also reported in D. svalbardicum a unique case of wing polymorphism with macropterous and micropterous forms in both genders. We named the second newly described parasitoid species Aphidius leclanti because of morphological similarities with other members of the Aphidius genus. Contrarily to D. svalbardicum, A. leclanti exploits the only two aphid species regularly found in Spitsbergen, A. svalbardicum and Sitobion calvulum. [Copyright &y& Elsevier]

The 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. [ABSTRACT FROM AUTHOR]