INDIRECT SELECTION OF STIGMA POSITION IN IPOMOPSIS AGGREGATA VIA A GENETICALLY CORRELATED TRAIT

Experimental manipulation of a trait can be used to distinguish direct selection from selection of correlated traits and to identify mechanisms of selection. Here we use experiments to investigate phenotypic selection of stigma position in angiosperm flowers. In natural populations of the subalpine herb Ipomopsis aggregata, plants with more strongly exserted stigmas receive more pollen per flower, indicating selection favoring stigma exsertion during the pollination stage of the life cycle. We pose four hypotheses for this association, two involving direct selection on stigma position and two involving indirect selection of a correlated floral trait. The first three hypotheses were tested using hand pollinations that mimicked natural hummingbird visitation, and by presenting captive hummingbirds with a series of flowers that differed in stigma and anther positions, sex ratio, and presence of anthers. In these experiments, pollen deposition either was independent of stigma exsertion or was highest on inserted stigmas, suggesting direct selection against exserted stigmas. In natural populations, however, stigma exsertion is highly correlated with time spent by the protandrous flowers in the pistillate phase. When we manipulated the latter trait in the field, pollen deposition increased with duration of exposure to hummingbirds, indicating indirect selection for stigma exsertion. Stigma exsertion and time spent in the pistillate phase are genetically and phenotypically correlated, as shown by a quantitative genetic experiment conducted in the field with paternal half sibships. Our results suggest that the evolution of stigma position can be driven by selection of a genetically correlated trait.     

山白树属及其近缘属聚类分析

运用系统聚类分析法,对山白树属及其近缘属进行定量分析,结果表明山白树属与牛鼻栓属亲缘关系密切,可组成一族,该族与蚊母树族有着较近的亲缘。     

Selecting for floral character associations in wild radish,Raphanus sativus L.

ESS models of reproductive allocation have been used extensively to explain patterns of floral diversity in angiosperms. These theoretical explorations assume that proportional allocation to pollen, ovules, and seeds, as well as to secondary features such as showy petals and nectar rewards, can evolve independently within the limits set by total resource availability. In populations of California wild radish, we have shown previously that petal size, a strong determinant of visitation by honey bee pollinators, is positively correlated with both pollen and nectar production, but not with ovule or seed number per flower. These phenotypic associations may reflect selection, environmental correlation, and/or genetic constraint. By exerting selection on the petal size : pollen number ratio over two generations, we eliminated the positive correlation between petal size and pollen production, with both characters showing significant change after a single selection episode. Once these two floral traits became uncoupled, nectar sugar production was significantly correlated only with petal size. Our results suggest that natural selection could readily alter reproductive allocation in these flowers, and that the phenotypic correlations observed in nature may be maintained by selection for effective reproductive phenotypes.     

膏桐花粉活力与柱头可授性及其生殖特性研究

采用TTC法测定了膏桐花粉的活力和寿命,用联苯胺-过氧化氢法测定其柱头可授期,以套袋结果检测花粉活力与柱头可授性的变化,以研究柱头颜色变化与柱头可授性的关系以及开花式样对生殖成功的影响.结果表明:(1)膏桐雄花单花花期一般为2 d,花后0~9 h内花粉活力相对较高,24~33 h后花粉活力较低,48 h后花粉基本无活力.(2)膏桐雌花单花期为5~12 d,柱头可授性在花后1~4 d最强,5~8 d可授性开始逐渐降低,第9天基本失去可授性.(3)膏桐柱头表面无明显的渗出物,柱头的可授性与柱头颜色的变化相关,柱头绿色越多,柱头可授性越强;遇降雨时,少量雌花的花瓣展开而柱头仍呈球状,或者花瓣不展开而柱头先伸出,此时柱头可授性较差.(4)膏桐常表现为雄性先熟,尽管雌花数目较少,但开放速率较快,且集中在第3~5天开放,雌花开放完毕也仍有雄花未开放,为展开后的柱头留有较长时间等候昆虫传送花粉,为保障生殖成功提供了机会,但少数花序先开雌花,后开雄花,有支持异交而降低自交的倾向.     

Effects of phenylacetaldehyde and (Z)-3-hexenyl acetate on male response to synthetic sex pheromone in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Abstract  The influence of two synthetic plant volatiles on the number of male Helicoverpa armigera (Hübner 1808) (Lepidoptera: Noctuidae) caught in sex pheromone-baited traps was studied in field plots in Australia. Phenylacetaldehyde and ( Z )-3-hexenyl acetate were combined with synthetic sex pheromone in traps. Generally, most males were captured in traps baited with pheromone alone and more males were captured by the mixture containing ( Z )-3 hexenyl acetate than that containing phenylacetaldehyde. At the three concentrations studied, neither volatile synergised the activity of the pheromone. Traps baited with the plant volatiles alone caught very few moths of either sex.     

柑桔提取物中主要成分的杀螨活性评价

【目的】研究柑桔提取物中主要杀螨活性成分,为柑桔提取物作为杀螨剂的使用奠定基础。【方法】采用乙醇、丙酮、乙酸乙酯、石油醚4种溶剂对北碚447的果皮与种子进行平行提取,对4种提取物进行杀螨活性评价。对北碚447的果皮乙醇提取物和乙酸乙酯提取物进行GC-MS分析,就其中主要成分进行杀螨活性评价,确定主要杀螨活性成分。【结果】发现柑桔乙醇提取物的杀螨活性最高;果皮提取物的杀螨活性高于种子;果皮和种子乙醇和乙酸乙酯提取物通过GC-MS分析共鉴定出35种成分,其中柠檬烯含量最高,和柠檬醛、4-松油醇、芳樟醇占提取物含量的85%以上;柠檬烯杀螨活性高于柠檬醛、松油醇、芳樟醇、?-蒎烯。【结论】柑桔提取物中主要的杀螨成分是柠檬烯、柠檬醛、4-松油醇、芳樟醇、?-蒎烯,以这些物质为主要有效成分的柑桔提取物类杀螨剂的研发具有重大意义。     

Reproductive biology of Pachira aquatica Aubl. (Malvaceae: Bombacoideae): a tropical tree pollinated by bats,sphingid moths and honey bees

We investigated the reproductive biology, including the floral biology, pollination biology, breeding system and reproductive success, of Pachira aquatica, a native and dominant tropical tree of fresh water wetlands, throughout the coastal plain of the Gulf of Mexico. The flowers present nocturnal anthesis, copious nectar production and sugar concentration (range 18–23%) suitable for nocturnal visitors such as bats and sphingid moths. The main nocturnal visitors were bats and sphingid moths while bees were the main diurnal visitors. There were no differences in legitimate visitation rates among bats, moths and honey bees. Bats and honey bees fed mainly on pollen while moths fed on nectar, suggesting resource partitioning. Eight species of bats carried pollen but Leptonycteris yerbabuenae is probably the most effective pollinator due to its higher pollen loads. The sphingid moths Manduca rustica, Cocytius duponchel and Eumorpha satellitia were recorded visiting flowers. Hand pollination experiments indicated a predominant outcrossing breeding system. Open pollination experiments resulted in a null fruit set, indicating pollen limitation; however, mean reproductive success, according to a seasonal census, was 17 ± 3%; these contrasting results could be explained by the seasonal availability of pollinators. We conclude that P. aquatica is an outcrossing species with a pollination system originally specialized for bats and sphingid moths, which could be driven to a multimodal pollination system due to the introduction of honey bees to tropical America.     

Antiherbivore defenses alter natural selection on plant reproductive traits

While many studies demonstrate that herbivores alter selection on plant reproductive traits, little is known about whether antiherbivore defenses affect selection on these traits. We hypothesized that antiherbivore defenses could alter selection on reproductive traits by altering trait expression through allocation trade‐offs, or by altering interactions with mutualists and/or antagonists. To test our hypothesis, we used white clover, Trifolium repens, which has a Mendelian polymorphism for the production of hydrogen cyanide—a potent antiherbivore defense. We conducted a common garden experiment with 185 clonal families of T. repens that included cyanogenic and acyanogenic genotypes. We quantified resistance to herbivores, and selection on six floral traits and phenology via male and female fitness. Cyanogenesis reduced herbivory but did not alter the expression of reproductive traits through allocation trade‐offs. However, the presence of cyanogenic defenses altered natural selection on petal morphology and the number of flowers within inflorescences via female fitness. Herbivory influenced selection on flowers and phenology via female fitness independently of cyanogenesis. Our results demonstrate that both herbivory and antiherbivore defenses alter natural selection on plant reproductive traits. We discuss the significance of these results for understanding how antiherbivore defenses interact with herbivores and pollinators to shape floral evolution.     

Early floral development and androecium organization in the sarracenioid clade (Actinidiaceae,Roridulaceae and Sarraceniaceae) of Ericales

The early floral development of Actinidia (A. arguta, A. callosa, A. chinensis and A. kolomikta; Actinidiaceae), Saurauia (S. montana, S. oldhamii, S. pittieri and S. subspinosa; Actinidiaceae), Roridula gorgonias (Roridulaceae) and Heliamphora nutans (Sarraceniaceae) was studied comparatively using scanning electron microscopy. Late stages of androecium development are additionally presented for Clematoclethra scandens (Actinidiaceae), Darlingtonia californica and Sarracenia leucophylla (Sarraceniaceae). Flowers are typically pentamerous and share a number of developmental features: perianth organs emerge in a clockwise or anticlockwise spiral sequence on the floral apex with relatively long plastochrons between successive organs, resulting in conspicuous size differences among perianth organs in early development; the perianth always consists of two differentiated whorls (unlike earlier interpretations of the perianth in Heliamphora); the androecium is polystemonous in most species and is initiated with leading stamens in alternipetalous positions; successive stamen primordia appear in a lateral succession until a ring‐like structure is formed; and the anthers become inverted shortly before anthesis. Later androecial development differs conspicuously between taxa and further proliferation may be centrifugal, centripetal and/or lateral. For Ericales, unusual features of floral development include: petals initiated in a spiral sequence (but later organized in a whorl) with comparatively long plastochrons between individual petals (except Saurauia); common occurrence of perianth organs in double positions in Actinidiaceae; and anthers that become inverted close to anthesis. The floral development in the sarracenioids is additionally compared with that of other families and clades in Ericales, further emphasizing the highly variable patterns of androecium development in the order.