Assortative Mating between European Corn Borer Pheromone Races: Beyond Assortative Meeting

BACKGROUND: Sex pheromone communication systems may be a major force driving moth speciation by causing behavioral reproductive isolation via assortative meeting of conspecific individuals. The 'E' and 'Z' pheromone races of the European corn borer (ECB) are a textbook example in this respect. 'Z' females produce and 'Z' males preferentially respond to a 'Z' pheromone blend, while the 'E' race communicates via an 'E' blend. Both races do not freely hybridize in nature and their populations are genetically differentiated. A straightforward explanation would be that their reproductive isolation is a mere consequence of "assortative meeting" resulting from their different pheromones specifically attracting males towards same-race females at long range. However, previous laboratory experiments and those performed here show that even when moths are paired in a small box - i.e., when the meeting between sexual partners is forced - inter-race couples still have a lower mating success than intra-race ones. Hence, either the difference in attractivity of E vs. Z pheromones for males of either race still holds at short distance or the reproductive isolation between E and Z moths may not only be favoured by assortative meeting, but must also result from an additional mechanism ensuring significant assortative mating at close range. Here, we test whether this close-range mechanism is linked to the E/Z female sex pheromone communication system. METHODOLOGY/PRINCIPAL FINDINGS: Using crosses and backcrosses of E and Z strains, we found no difference in mating success between full-sisters emitting different sex pheromones. Conversely, the mating success of females with identical pheromone types but different coefficients of relatedness to the two parental strains was significantly different, and was higher when their genetic background was closer to that of their male partner's pheromone race. CONCLUSIONS/SIGNIFICANCE: We conclude that the close-range mechanism ensuring assortative mating between the E and Z ECB pheromone races is unrelated to the difference in female sex pheromone. Although the nature of this mechanism remains elusive, our results show that it is expressed in females, acts at close range, segregates independently of the autosome carrying Pher and of both sex chromosomes, and is widely distributed since it occurs both in France and in the US

Leaf Stomatal Conductance and Photosynthesis of Field-grown Maize Exposed to Changing Ozone Concentrations

The impacts of moderate oz one levels on leaf conduct ance and photosynthesis of maize were assessed from field fumigation expe riments carried out at Grignon (France) in july-august 2011. The expo sition of the plants to ozone was achieved by a linear fumigation device. Continuous measurements of ozone concentration were taken inside th e vegetation, close to the ears. The mean daylight ozone le vels ranged from 31 ppb (control) to 59 ppb. Although photosynthesi s was significantly affected by long-term oz one exposure, stomatal conductance appear ed to be moderately sensitive to this pollutant . Furthermore, grain yields were very slightly impa cted. A Jarvis-type model of stomatal conductance was used in order to establish an empirical relationship between stomatal uptake of ozone and photosynthetic capacity

Leaf Stomatal Conductance and Photosynthesis of Field-grown Maize Exposed to Changing Ozone Concentrations

The impacts of moderate ozone levels on leaf conductance and photosynthesis of maize were assessed from field fumigation experiments carried out at Grignon (France) in july-august 2011. The exposition of the plants to ozone was achieved by a linear fumigation device. Continuous measurements of ozone concentration were taken inside the vegetation, close to the ears. The mean daylight ozone levels ranged from 31 ppb (control) to 59 ppb. Although photosynthesis was significantly affected by long-term ozone exposure, stomatal conductance appeared to be moderately sensitive to this pollutant. Furthermore, grain yields were very slightly impacted. A Jarvis-type model of stomatal conductance was used in order to establish an empirical relationship between stomatal uptake of ozone and photosynthetic capacity

Estimation of the reduction in photosynthetic parameters (Vpmax, Vcmax) in the leaves of maize plants exposed to increasing ozone concentrations

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Carbon stable isotopes: a tool for studying the mating, oviposition, and spatial distribution of races of European corn borer, Ostrinia nubilalis , among host plants in the field

International audienceThe European corn borer, Ostrinia nubilalis (Hübner, 1796) (Lepidoptera: Crambidae), is a polyphagous corn pest species that includes two host races: one feeding on corn (Zea mays L.) and one feeding on mugwort (Artemisia vulgaris L.) and hop (Humulus lupulus L.). Being able to determine the type of host plant on which field-caught moths fed as larvae would allow for the quantification of mating rates within and between races, as well as the quantification of the spatial distribution and oviposition of both races in the field. We found that stable carbon isotopes (δ13C) are areliable indicator of host-plant photosynthetic type (C3 or C4) regardless of adult food and intensity of metabolism; so even when food or metabolism had a significant effect on wing δ13C values, the magnitude of this effect was too small to obscure the signal characterizing host-plant type. Egg and spermatophore δ13C values similarly reflect female and male host-plant type, respectively, regardless of adult feeding. We found 224 host-plant species of O. nubilalis in the literature, including 19 species with C4-type photosynthesis. However, in temperate areas, corn is probably the only significant C4 source of adult moths. Accordingly, wing δ13C values were more variable in field-caught moths showing a typical C3-type δ13C value than in those showing a typical C4-type δ13C value.La pyrale du maïs, Ostrinia nubilalis (Hübner, 1796) (Lepidoptera : Cram1b1i8d5ae), est une espèce polyphage ravageuse du maïs, divisée en une race se nourrissant sur le maïs (Zea mays L.) et une race se nourrissant sur l’armoise (Artemisia vulgaris L.) et le houblon (Humulus lupulus L.). La détermination du type de plante hôte sur lequel des adultes capturés in natura se sont développés à l’état larvaire permettrait de quantifier, en conditions naturelles, les taux de croisements intra- et inter-races, ainsi que la distribution spatiale et l’oviposition des individus issus des deux races. Nous montrons ici que les isotopes stables du carbone sont des indicateurs fiables du type photosynthétique (C3 ou C4) des plantes hôtes, et ce quels que soit le type de nourriture consommé par les adultes et l’intensité de leurmétabolisme. En effet, bien que la nourriture ou le métabolisme des adultes aient un effet significatif sur la teneur en δ13C des ailes, l’intensité de ces effets est trop faible pour brouiller le signal provenant de la plante hôte. De même, les valeurs de δ13C des pontes et des spermatophores reflètent parfaitement la plante hôte d’origine respectivement des femelles et des mâles, et ce indépendamment du régime alimentaire des papillons. Dans la littérature, nous avons répertorié 224 espèces de plantes hôtes d’O. nubilalis, dont 19 ont un type photosynthétique C4. Toutefois, le maïs est probablement la seule source significative d’adultes issus de plantes en C4 en zone tempérée. De manière concordante, les valeurs de δ13C des ailes de papillons capturés in natura sont plus variables chez les individus présentant des valeurs de δ13C typiques de C3 que chez les individus présentant des valeurs de δ13C typiques de C4

Water Use Efficiency in Field-Grown Maize : Effects of Soil Structure

* INRA, centre de Grignon, posterInternational audienc

Vacuolar endoproteolytic activities and protein carbonylation levels in leaf as a model for depicting ozone tolerance and sensitivy in winter wheat (Trticum aestivum L.).

Vacuolar endoproteolytic activities and protein carbonylation levels in leaf as a model for depicting ozone tolerance and sensitivy in winter wheat (Trticum aestivum L.).. 27. Task Force Meeting of the ICP Vegetatio