Buddleja davidii and Buddleja yunnanensis: Exploring features associated with commonness and rarity in Buddleja

Buddleja davidii is a widespread shrub in Asia while B. yunnanensis is a narrowly endemic species limited to Yunnan Province, China. To explore whether floral volatiles, morphological characters of flower and seed and breeding system are correlated with their distributions, we measured length and width of corolla, trichome density at corolla throat, level of stigma/anthers relationship, seed size and weight. The results indicated that these characteristics were significantly different between the two species (P < 0.01). Bagging experiments revealed that B. davidii is a self-incompatible plant while B. yunnanensis is self-compatible. Thick trichome density at the corolla throat may reduce out-crossing in B. yunnanensis. Autogamy plays an important role in fruit production of this species while B. davidii requires pollinators for fruiting. Scents were collected using dynamic headspace adsorption method and identified with coupled gas chromatography and mass spectrometry. In total, 27 floral scent compounds were identified. The volatile composition in the two species was very different. We attempted to determine if these features, associated with commonness and with rarity found in these two taxa, could also help to explain the distribution pattern of other species of the genus Buddleja.     

Gastrophysa polygoni herbivory on Rumex confertus: single leaf VOC induction and dose dependent herbivore attraction/repellence to individual compounds

We report large induction (>65_fold increases) of volatile organic compounds (VOCs) emitted from a single leaf of the invasive weed mossy sorrel, Rumex confertus Willd. (Polygonaceae), by herbivory of the dock leaf beetle, Gastrophysa polygoni L. (Coleoptera: Chrysomelidae). The R. confertus VOC blend induced by G. polygoni herbivory included two green leaf volatiles ((Z)-3-hexenal, (Z)-3-hexen-1-yl acetate) and three terpenes (linalool, ß-caryophyllene, (E)-ß-farnesene). Uninjured leaves produced small constitutive amounts of the GLVs and barely detectable amounts of the terpenes. A Y-tube olfactometer bioassay revealed that both sexes of adult G. polygoni were attracted to (Z)-3-hexenal and (Z)-3-hexen-1-yl acetate at a concentration of 300 ng h⁻¹. No significant G. polygoni attraction or repellence was detected for any VOC at other concentrations (60 and 1500 ng h⁻¹). Yet, G. polygoni males and females were significantly repelled by (or avoided) at the highest test concentration (7500 ng h⁻¹) of both GLVs and (E)-ß-farnesene. Mated male and female G. polygoni might be attracted to injured R. confertus leaves, but might avoid R. confertus when VOC concentrations (especially the terpene (E)-ß-farnesene) suggest high overall plant injury from conspecifics, G. viridula, or high infestations of other herbivores that release (E)-ß-farnesene (e.g., aphids). Tests in the future will need to examine G. polygoni responses to VOCs emitted directly from uninjured (constitutive) and injured (induced) R. confertus, and examine whether R. confertus VOC induction concentrations increase with greater tissue removal on a single leaf and/or the number of leaves with feeding injury.     

Blow fly responses to semiochemicals produced by decaying carcasses

Volatiles from mouse carcasses in decay stages ranging from fresh to 33 days old were used to investigate oriented flight and landings in male and female blow flies of Calliphora vicina Robineau‐Desvoidy (Diptera: Calliphoridae). Oriented flight increased significantly from 36% towards fresh carcasses to 68%, 61% and 65% towards carcasses aged 3 days, 6 days and 9 days, respectively. Carcasses aged 20 days and 33 days were significantly less attractive, achieving 51% and 41% attraction, respectively. No differences emerged between the sexes in oriented flight, but a significant increase in female landings at the most attractive carcasses was observed. Headspace collections from the different stages of decay showed a succession in the volatile profile emitted from the carcasses and identified nine chemicals which peak in quantity in concurrence with the most attractive stages of decay. Three of these chemicals also showed dose–response effects as indicated by a significant correlation between the amount present and the proportion of flies responding. Blow flies are important pests and efficient traps are needed. The significant interaction between fly sex and carcass age highlights behavioural differences between male and female blow flies which can be exploited in blow fly trapping. Three new volatile chemicals, butylated hydroxyl toluene, 3‐hydroxy‐2‐butanone and nonanal, emitted from dead mice are suggested as potential attractants.     

Niche construction initiates the evolution of mutualistic interactions

Niche construction theory explains how organisms' niche modifications may feed back to affect their evolutionary trajectories. In theory, the evolution of other species accessing the same modified niche may also be affected. We propose that this niche construction may be a general mechanism driving the evolution of mutualisms. Drosophilid flies benefit from accessing yeast‐infested fruits, but the consequences of this interaction for yeasts are unknown. We reveal high levels of variation among strains of Saccharomyces cerevisiae in their ability to modify fruits and attract Drosophila simulans. More attractive yeasts are dispersed more frequently, both in the lab and in the field, and flies associated with more attractive yeasts have higher fecundity. Although there may be multiple natural yeast and fly species interactions, our controlled assays in the lab and field provide evidence of a mutualistic interaction, facilitated by the yeast's niche modification.     

青杨脊虎天牛对植物源挥发物的EAG和行为反应

测定了青杨脊虎天牛Xylotrechus rusticus （L.）雌、雄成虫对其寄主杨树中的水杨醛（0.95 μmol/μL）和非寄主植物中0.3 μmol/μL的叶绿醇、0.4 μmol/μL的水芹烯和0.6 μmol/μL的 R 型α-蒎烯、S 型α-蒎烯、S型β-蒎烯、3-蒈烯、罗勒烯、香草烯和松节油等10种植物挥发性气味物质的触角电位（EAG）反应。结果表明,与对照相比,这10种植物挥发物多能引起成虫明显的EAG反应( P<0.05,P<0.01 ),其中雌虫对松节油、水杨醛、R 型α-蒎烯和 S 型α-蒎烯的EAG反应较强; 雄虫对 R 型α-蒎烯的EAG反应最强,松节油次之。根据雌虫对这10种挥发物EAG反应的强弱,进一步测定了雌虫对0.00006、0.0006、0.006、0.06、0.6、0.12 μmol/μL的松节油、R 型α-蒎烯、S 型α-蒎烯以及0.000095、0.00095、0.0095、0.095、0.95、0.19 μmol/μL的水杨醛的EAG和行为反应。结果表明,雌虫对松节油、水杨醛和 R 型α-蒎烯的EAG反应随气味物质浓度的增加而增加,水杨醛浓度增加到0.95 μmol/μL、松节油和 R 型α-蒎烯浓度增加到0.6 μmol/μL以后,EAG反应值趋于平稳;对 S 型α-蒎烯的反应随浓度的增加而呈线性增加。水杨醛浓度低于0.095时,对雌虫没有明显的定向作用( P>0.05 ),高于此浓度时表现为驱避作用( P<0.05 ); 松节油在浓度低于或等于0.6 μmol/μL时对雌虫表现为驱避作用,浓度为0.6时驱避效果最佳（ P<0.01 ）。雌虫对 R 型α-蒎烯和 S 型α-蒎烯没有明显的定向行为反应。     

一种测定植物挥发物对棉铃虫引诱作用的无选择性风洞嗅觉仪(英文)

发展了一套测定棉铃虫Helicoverpaarmigera (H櫣ｂｎｅｒ)对植物挥发物的行为反应的生测系统。这套系统由嗅觉仪、风洞和风洞室组成。用这套系统测定了棉铃虫对萎蔫后的枫杨Pterocaryastenoptera叶、加拿大杨Populuscanadensis叶、香椿Toonasisnensis叶、新鲜的芹菜与胡萝卜花挥发物以及苯乙醛的行为反应。结果显示 ,萎蔫的枫杨叶、加拿大杨叶、香椿叶的挥发物均对棉铃虫处女雌蛾表现出显著的引诱作用 ,而对已交配过的雌蛾和雄蛾无明显的引诱作用 ;新鲜的芹菜与胡萝卜花挥发物对棉铃虫两性性成虫均不表现出显著的引诱作用 ;苯乙醛对棉铃虫处女雌、雄蛾有较强的引诱作用。讨论了杨树枝把引诱棉铃虫的原因。     

The role of chemical cues in host finding and acceptance by Callosobruchus chinensis

We studied the response of female Callosobruchus chinensis to chemical cues emitted by cowpea seeds at different stages of bruchid infestation (uninfested, egg carrying, L1-, and L4-infested). Olfactory attractiveness was determined in Y-tube olfactometer assays by testing individual seed categories against either clean air or uninfested seeds. Oviposition preferences between uninfested and infested seeds were determined in petri-dish choice-experiments. The olfactometer assays revealed that weevils discriminate between seeds containing different stages of developing bruchids on the basis of olfactory cues. While odors from uninfested and egg-carrying seeds acted as attractants, odors from L1- and L4-infested seeds failed to induce a positive response by the bruchids. When given a choice between uninfested and infested seeds in the olfactometer, weevils preferred uninfested seeds over L1- and L4-infested seeds, but failed to distinguish between uninfested and egg-carrying seeds. In the oviposition experiment as well, bruchids showed a distinct preference for uninfested seeds when offered in combination with L1- and L4-infested seeds. This experiment further showed a reduced acceptance of egg carrying seeds. Our results indicate that C. chinensis females use chemical information during both host searching and host acceptance. Volatiles from uninfested or egg carrying seeds act as attractants, while deterrence increases as development of bruchid immature stages progresses.     

草地螟对寄主植物的选择性及其化学生态机制

田间自然条件下,草地螟成虫产卵对不同植物具有明显的选择性,其中灰菜上落卵量最多,占调查总卵量的50%以上;甜菜、大豆上次之,玉米和马铃薯上最少。在室内条件下,草地螟成虫产卵对灰菜、大豆、玉米和马铃薯的选择性与田间调查结果完全吻合。而且,草地螟幼虫的嗜食性与成虫产卵对寄主的选择性是一致的。吸附、收集上述植物的挥发物后进行GC-MS测定,并利用风洞进行了生测。其中灰菜和大豆的主要挥发物成分为反-2-己烯醛、青叶醇、青叶酯、1-十八烯等;玉米和马铃薯的挥发物性成分包括青叶酯、芳樟醇、香叶醇、紫罗酮、1-十八烯。生测结果表明,灰菜的挥发物对草地螟雌蛾引诱力最大,选择系数为78%;大豆苗挥发物对其也有较高的诱虫活性;但玉米和马铃薯几乎无引诱作用。自然生长的4种植物的诱虫结果与其挥发物的诱虫结果相似。这些生测结果与成虫和幼虫选择寄主的一致性反映了草地螟选择寄主行为的化学机制。