Springer Online Journal Archives 1860-2000
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Summary The production of sexual morphs was compared for French clones of S. avenae. Sal was collected in the Rennes basin (West of France), Sa2 by the seaside in the Pas de Calais (North of France) and Sa3 near Angoulême in the south-western part of the country. 1): aphids of Sal and Sa2 were reared at three constant temperature-photoperiod conditions: 10°C/12 L; 15°C/12 L and 20°C/16 L. Males were produced by both clones at 10°C/12 L and 15°C/12 L. More of them were produced at 15°C than at 10°C with some interclonal differences. The clones differed mainly by their ability to produce gynoparae and oviparae. Sal produced them only at 15°C/12 L and Sa2 only at 10°C/12 L. Gynoparae of Sa2 produced only oviparae whereas those of Sal produced a mixture of oviparae and virginoparae specially at the end of the reproducing sequence. A large part of both clonal populations did not turn into sexual morphs and remained parthenogenetic until the 3rd generation. 2): aphids of Sal, Sa2 and Sa3 were exposed to decreasing photoperiods and temperatures simulating two summer-autumn climatic sequences, only different by cumulated temperatures. Starting mid October males were produced by the three clones under both climatic sequences, but more under the warmer than under the colder sequence. When produced, oviparae occured at the same period than males did. For Sa2 oviparae were produced under both climatic sequences and in reduced quantities. For Sal and Sa3 oviparae were only produced under the warmer climatic sequence but in large number for Sal and in reduced number for Sa3. It was shown that the three clones were genetically holocyclic and probably able to produce some sexual morphs outside normal autumn conditions. The differences between these results and some others obtained with British clones were discussed. They may be due to clonal differences in the degree of evolution of S. avenae from heteroecy to monoecy.
Abstract On a comparé les modalités de la production de formes sexuées par deux ou trois clônes de Sitobion avenae F. originaires de régions océaniques de la France. Deux expérimentations ont été faites, l'une en conditions climatiques constantes et l'autre en conditions simulant un climat d'automne. Les trois clônes sont génétiquement holocycliques et deux d'entre eux, étudiés plus en détail, diffèrent par certaines modalités de leur production de sexués, l'un formant en particulier des femelles ovipares à 10°C/12 h de photophase et l'autre à 15°C/12 h de photophase. Au contraire, ces clônes conservent des caractères généraux identiques, ils forment des andropares aptères et des gynopares ailés. Ils paraissent ainsi moins dégradés par rapport au type primitif hétéroécique qu'un autre clône étudié en Grande-Bretagne. Les limits d'extrapolation de ces résultats à ce qui se passe dans la nature sont discutées.
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