Phenological synchrony affects interaction strength of an exotic weevil with Platte thistle,a native host plant

Phenological synchrony of a consumer population with its resource populations is expected to affect interaction intensity. We quantified phenological variation and synchrony of populations of an invasive Eurasian flower head weevil, Rhinocyllus conicus, that consumes florets, ovules, and seeds of developing flower heads of a native North American thistle, Cirsium canescens, in Sand Hills prairie in Nebraska, USA. Variation in timing of adult activity among weevil populations was larger than variation in timing of flower head development among C. canescens populations, and it drove the observed variation in the phenological synchrony between weevil and host plant populations. Furthermore, the degree of phenological synchrony between populations was significant in explaining variation in weevil egg load on the newly acquired host plant. Because population growth of C. canescens is limited by predispersal seed losses to floral herbivores, variation in the synchrony of herbivore and plant flowering will affect the density of the plant population. These results provide strong quantitative support for the hypothesis that the synchrony of insect activity with plant resources can determine the magnitude of impact of floral herbivores on their host plant populations.     

Inter-annual variation in above- and belowground herbivory on a native,annual legume

The relative importance of subterranean versus aboveground insect damage to plants is not well understood. In particular, the simultaneous effects of above- and belowground herbivory, and the importance of highly variable abiotic factors such as rainfall, have received little attention in diverse natural ecosystems. We investigated the influence of both above- and belowground herbivory on Lupinus nanus (Fabaceae), an annual plant native to coastal California. A number of insect species damage L. nanus aboveground, and a weevil larva consumes nodules belowground. To manipulate herbivory in the field, we employed a combination of insecticides and simulated herbivory during two different years. In 1997, simulated belowground damage reduced L. nanus survival, and insecticide application to roots increased seed production and seed mass. By contrast, in 1998, only aboveground folivory significantly reduced L. nanus reproduction, and, in combination, above- and belowground insecticides did not affect flower or seed number relative to controls. A growth chamber experiment conducted in the absence of herbivory revealed that the aboveground insecticide marginally reduced flower production and the belowground insecticide marginally increased flower production compared to controls; these non-target effects made our field experiments for aboveground herbivory conservative. Finally, ambient levels of herbivory differed among years (1997, 1998, and 2000), which varied greatly in rainfall due to the effects of El Nino. The results suggest that the impacts of herbivores are temporally variable and that abiotic factors, particularly those related to large-scale changes in weather patterns, may be more important than insect herbivory to L. nanus in some years. This revised version was published online in August 2006 with corrections to the Cover Date.     

Floral herbivore effect on the sex expression of an andromonoecious plant,Isomeris arborea (Capparaceae)

Flower-feeding insects may influence the reproductive behavior of their host plant. In plants with labile sex expression, the ratio of maternal to paternal investment may change in response to damage, an effect that goes beyond the direct reduction of plant gametes. We examined the effects of floral herbivory by the beetle Meligethes rufimanus (Nitidulidae) on the ratio of hermaphroditic flowers to male flowers in an andromonoecious shrub, Isomeris arborea (Capparaceae) in southern California. Plants exposed to herbivory had a greater rate of flower bud abortion than those protected from herbivory. Exposed plants produced a greater proportion of hermaphroditic flowers to male flowers, although damaged inflorescences still produced fewer fruit. An additional manipulative experiment showed that the removal of pistils on inflorescences led to an increase in the proportion of hermaphroditic flowers. This suggests that the presence of fruit may lead to pistil suppression in developing flowers. Adaptive responses to herbivory which favor andromonoecy thus include the continued production of hermaphroditic flowers when floral damage is high (and hence low fruit set), and a switch to male flower production when floral damage is low (and fruit production increases). The consequences of an altered six ratio induced by insect herbivores may lead to indirect effects on both the male and female reproductive success of this plant.     

Floral herbivory at different stages of flower development changes reproduction in <Emphasis Type="Italic">Iris gracilipes</Emphasis> (Iridaceae)

Floral herbivores and pollinators are major determinants of plant reproduction. Because interaction of floral herbivores and pollinators occurs when herbivores attack the flowers in the bud and flower stages and because the compensatory ability of plants is known to differ according to the timing of herbivory, the effects of herbivory may differ according to its timing. In this study, we investigated the effects of floral herbivory at different stages on fruit production and seed/ovule ratio at two sites of large populations of the perennial herb, Iris gracilipes for 2 years. Herbivory at the bud and fruit stages both tended to have negative effects on fruit production, but the former caused more severe damage. On the other hand, herbivory at the flower stage tended not to have negative effects on fruit production because the degree of flower loss was smaller in the flower stage. Although herbivory decreased fruit production, flowers did not compensate for the damage by increasing the seed/ovule ratio because reproduction of I. gracilipes was limited by pollen availability rather than resources. These results indicate that floral herbivory at different stages has different effects on plant reproduction.     

Effects of floral herbivory on foraging behaviour of bumblebees and female reproductive success in Pedicularis gruina (Orobanchaceae)

The effects of floral herbivores on floral traits may result in alterations in pollinator foraging behaviour and subsequently influence plant reproductive success. Fed-upon plants may have evolved mechanisms to compensate for herbivore-related decreased fecundity. We conducted a series of field experiments to determine the relative contribution of floral herbivores and pollinators to female reproductive success in an alpine herb, Pedicularis gruina, in two natural populations over two consecutive years. Experimental manipulations included bagging, hand supplemental, geitonogamous pollination, and simulated floral herbivory. Bumblebees not only avoided damaged flowers and plants but also decreased successive visits of flowers in damaged plants, and the latter may reduce the level of geitonogamy. Although seed set per fruit within damaged plants was higher than that in intact plants, total seed number in damaged plants was less than that in intact plants, since floral herbivory-mediated pollinator limitation led to a sharp reduction of fruit set. Overall, the results suggest that resource reallocation within inflorescences of damaged plants may partially compensate for a reduction in seed production. Additionally, a novel finding was the decrease in successive within-plant bumblebee visits following floral herbivory. This may increase seed quantity and quality of P. gruina since self-compatible species exhibit inbreeding depression. The patterns of compensation of herbivory and its consequences reported in this study give an insight into the combined effects of interactions between floral herbivory and pollination on plant reproductive fitness.     

Altered patterns of growth, physiology and reproduction in invasive genotypes of Solidago gigantea (Asteraceae)

Introduced plants may leave their specialized herbivores behind when they invade new ranges. The Evolution of Increased Competitive Ability (EICA) Hypothesis holds that this escape from herbivory could lead to reduced investment in defenses, thereby freeing resources for growth and reproduction. We tested the prediction that introduced genotypes of Solidago gigantea would outperform native genotypes when grown in the absence of herbivores, and examined whether tolerance to insect herbivory has changed in introduced genotypes. S. gigantea is native to North America and an exotic invasive in Europe. Insect damage reduced plant growth and biomass for both native and exotic genotypes. While there was no evidence that continent of origin influenced the degree to which plants compensated for herbivory, the mechanisms contributing to recovery differed for native and exotic plants. Damaged US plants showed enhanced photosynthetic rates to a greater extent than damaged European plants, while damaged European plants carried more leaves than damaged US plants. At the end of the season, leaf mass of European plants was significantly greater than that of US plants. Contrary to the predictions of the EICA hypothesis, US plants were more likely to flower than European plants. European plants invested significantly more of their total reproductive biomass into rhizomes rather than flowers than US plants. While other work with S. gigantea has supported some aspects of the EICA hypothesis, the results reported here generally do not. We conclude that multiple factors influence the success of introduced plants.     

Nonadditive effects of flower damage and hummingbird pollination on the fecundity of Mimulus luteus

Flower herbivory and pollination have been described as interactive processes that influence each other in their effects on plant reproductive success. Few studies, however, have so far examined their joint effects in natural populations. In this paper we evaluate the influence of flower damage and pollination by the hummingbird Oreotrochilus leucopleurus on the fecundity of the Andean monkey flower Mimulus luteus. We performed a 2×2 factorial experiment, with artificial clipping of lower petals and selective exclusion of the hummingbird as main factors. In spite of the relatively low proportion (27.5%) of the variance in seed production accounted for by the full factorial model, artificial damage and hummingbird exclusion, as well as their interaction, were highly significant, indicating nonadditive effects of factors on plant fecundity. In the presence of hummingbirds, undamaged flowers had a seed production that was 1.7-fold higher than for damaged flowers, suggesting that the effect of flower damage on female reproductive success occurs probably as a consequence of hummingbird discrimination against damaged corollas. This result indicates that the impact of flower herbivory on plant fecundity was contingent on the presence or absence of hummingbirds, suggesting that pollinators may indirectly select for undamaged and probably resistant flower phenotypes. A second interaction effect revealed that undamaged flowers produced 78.5% more seeds in the absence of rather than in the presence of O. leucopleurus, raising the question of the ecological mechanism involved. We suggest that the strong territorial behavior exhibited by the bee Centris nigerrima may confine the foraging activities of the remaining bee species to safe sites within exclosures. Overall, our results provide evidence that hummingbird pollination and flower herbivory have interdependent effects on M. luteus fecundity, which indicates that it will be difficult to predict their ecological and evolutionary consequences unless interactions are analyzed in an integrated form.     

Multiple herbivores and coevolutionary interactions in an Ipomopsis hybrid swarm

Studies focusing on pairwise interactions between plants and herbivores may not give an accurate picture of the overall selective effect of herbivory, given that plants are often eaten by a diverse array of herbivore species. The outcome of such interactions may be further complicated by the effects of plant hybridization. Hybridization can lead to changes in morphological, phenological and chemical traits that could in turn alter plant–herbivore interactions. Here we present results from manipulative field experiments investigating the interactive effects of multiple herbivores and plant hybridization on the reproductive success of Ipomopsis aggregata formosissima X I. tenuituba. Results showed that ungulate herbivores alone had a net positive effect on plant relative fitness, increasing seed production approximately 2-fold. Caterpillars had no effect on plant relative fitness when acting alone, with caterpillar-attacked plants producing the same number of flowers, fruits and seeds as the uneaten controls. Caterpillars, however, significantly reduced flower production of ungulate browsed plants. Flower production in these plants, however, was still significantly greater (approximately 1.7-fold greater) than uneaten controls, likely leading to an increase in reproductive success through the paternal component of fitness given that fruit and seed production was not significantly different from that of herbivore-free controls. Although results suggest that herbivore imposed selection is pairwise, ungulates likely have a large influence on the abundance of, and hence the amount of damage caused by, caterpillar herbivores. Thus, because of the ecological interactions between ungulates and caterpillars, selection on Ipomopsis may be diffuse rather than pairwise, assuming such interactions translate into differential effects on plant fitness as herbivore densities vary. Plant hybridization had no significant effect on patterns of ungulate or caterpillar herbivory; i.e., no significant interactions were detected between herbivory and plant hybridization for any of the fitness traits measured in this study nor did plant hybridization have any significant effect on host preference. These results may be due to patterns of introgression or the lack of species-specific differences between I. aggregate formosissima and I. tenuituba. Plant hybridization per se resulted in lowered reproductive success of white colored morphs due in part to the effects of pollination. Although it appears that there would be strong directional selection favoring darker flower colors due to the lower reproductive success of the white colored morphs in the short run, the natural distribution of hybrids suggest that over the long run selection either tends to average out or there are no fitness differences among morphs in most years due to the additive fitness effects of hawkmoth and hummingbird pollinators.     

Floral trait expression and plant fitness in response to below- and aboveground plant–animal interactions

Although plant–animal interactions like pollination and herbivory are obviously interdependent, ecological investigations focus mainly on one kind of interaction ignoring the possible significance of the others. Plants with flowers offer an extraordinary possibility to study such mutualistic and antagonistic interactions since it is possible to measure changes in floral traits and fitness components in response to different organisms or combinations of them. In a three factorial common garden experiment we investigated single and combined effects of root herbivores, leaf herbivores and decomposers on flowering traits and plant fitness of Sinapis arvensis. Leaf herbivory negatively affected flowering traits indicating that it could significantly affect plant attractiveness to pollinators. Decomposers increased total plant biomass and seed mass indicating that plants use the nutrients liberated by decomposers to increase seed production. We suggest that S. arvensis faced no strong selection pressure from pollen limitation, for two reasons. First, reduced nutrient availability through leaf herbivory affected primarily floral traits that could be important for pollinator attraction. Second, improved nutrient supply through decomposer activity was invested in seed production and not in floral traits. This study indicates the importance of considering multiple plant–animal interactions simultaneously to understand selection pressures underlying plant traits and fitness.     

Sex‐biased seed predation in gynodioecious Dianthus superbus var. longicalycinus (Capryophyllaceae) and differential influence of two seed predator species on the floral traits

Gynodioecy, the co‐occurrence of hermaphrodite and female individuals within a species, is maintained by differential reproductive success between sexes. Recently, researchers recognized that not only pollinators but also herbivores are important agents in the evolution and maintenance of gynodioecy, when herbivory is hermaphrodite biased. In this study, we investigated whether there is hermaphrodite‐biased herbivory in a gynodioecious plant, Dianthus superbus var. longicalycinus, and if so, what floral traits influenced hermaphrodite‐biased herbivory. We measured flower morphology (flower diameter, calyx tube length, corolla height and petal width) and phenology of flowers of female individuals, hermaphrodites and gynomonoecious individuals in a natural population. We also investigated seed predation and predator species. At the study site, Sibinia weevils (Curculionidae; Coleoptera) and Coleophora moths (Coleophoridae; Lepidoptera) were common pre‐dispersal seed predators in this species. The weevil appeared early in the flowering season, and weevil predation correlated with flower phenology. Because female individuals did not flower early in the season, weevil predation was less frequent in female individuals. Moth predation correlated with calyx length. The calyx length of flowers of female individuals was smaller than those of hermaphrodites, but a direct comparison of moth predation rates failed to find a significant difference among sex morphs. We found that the two seed predators had different effects on floral traits in D. superbus var. longicalycinus. We suggest that weevil predation contributes to the maintenance of gynodioecy because female individuals successfully escaped weevil predation by flowering late. It remains unclear why flower phenology is different among sex morphs.     

Effects of foliar herbivory by insects on the fitness of Raphanus raphanistrum: damage can increase male fitness

Generally, effects of herbivory on plant fitness have been measured in terms of female reproductive success (seed production). However, male plant fitness, defined as the number of seeds sired by pollen, contributes half of the genes to the next generation and is therefore crucial to the evolution of natural plant populations. This is the first study to examine effects of insect herbivory on both male and female plant reproductive success. Through controlled field and greenhouse experiments and genetic paternity analysis, we found that foliar damage by insects caused a range of responses by plants. In one environment, damaged plants had greater success as male parents than undamaged plants. Neither effects on pollen competitive ability nor pollinator visitation patterns could explain the greater siring success of these damaged plants. Success of damaged plants as male parents appeared to be due primarily to changes in allocation to flowers versus seeds after damage. Damaged plants produced more flowers early in the season, but not more seeds, than undamaged plants. Based on total seed production, male fitness measures from the first third of the season, and flower production, we estimated that damaged and undamaged plants had equal total reproductive success at the end of the season in this environment. In a second, richer environment, damaged and undamaged plants had equal male and female plant fitness, and no traits differed significantly between the treatments. Equal total reproductive success may not be ecologically or evolutionarily equivalent if it is achieved differentially through male versus female fitness. Genes from damaged plants dispersed through pollen may escape attack from herbivores, if such attack is correlated spatially from year to year.     

Indirect interaction between two native thistles mediated by an invasive exotic floral herbivore

Spatial and temporal variation in insect floral herbivory is common and often important. Yet, the determinants of such variation remain incompletely understood. Using 12 years of flowering data and 4 years of biweekly insect counts, we evaluated four hypotheses to explain variation in damage by the Eurasian flower head weevil, Rhinocyllus conicus, to the native North American wavyleaf thistle, Cirsium undulatum. The four factors hypothesized to influence weevil impact were variations in climate, weevil abundance, phenological synchrony, and number of flower heads available, either on wavyleaf thistle or on the other cooccurring, acquired native host plant (Platte thistle, Cirsium canescens), or on both. Climate did not contribute significantly to an explanation of variation in R. conicus damage to wavyleaf thistle. However, climate did influence weevil synchrony with wavyleaf flower head initiation, and phenological synchrony was important in determining R. conicus oviposition levels on wavyleaf thistle. The earlier R. conicus was active, the less it oviposited on wavyleaf thistle, even when weevils were abundant. Neither weevil abundance nor availability of wavyleaf flower heads predicted R. conicus egg load. Instead, the strongest predictor of R. conicus egg load on wavyleaf thistle was the availability of flower heads on Platte thistle, the more common, earlier flowering native thistle in the sand prairie. Egg load on wavyleaf thistle decreased as the number of Platte thistle flower heads at a site increased. Thus, wavyleaf thistle experienced associational defense in the presence of flowering by its now declining native congener, Platte thistle. These results demonstrate that prediction of damage to a native plant by an exotic insect may require knowledge of both likely phenological synchrony and total resource availability to the herbivore, including resources provided by other nontarget native species.     

Induced defense in Nicotiana attenuata (Solanaceae) fruit and flowers

Plants protect themselves against herbivory using a continuum of strategies, ranging from constitutive defenses to intermittent induced responses. Induced defenses may not provide immediate and maximum protection, but could be advantageous when continuous defense is either energetically or ecologically costly. As such, induced defenses in flowers could help defend relatively valuable tissue while keeping reproductive structures accessible and attractive to pollinators. Thus far, no one has demonstrated the efficacy of induced defenses against floral herbivores (florivores) in the field. Here we show that mechanical leaf damage in wild tobacco, Nicotiana attenuata (Solanaceae), reduced both flower and fruit herbivory in the field and that exogenous application of methyl jasmonate, a potent elicitor of induced responses, reduced both leaf and floral damage in natural populations. This result is consistent with a survey of damage in the field, which showed a negative relationship between leaf damage and flower and fruit damage. Although optimal defense theory predicts that induced defenses should be rare in reproductive tissues, owing to their high fitness value, our results suggest otherwise. Induced defenses in leaves and reproductive tissues may allow plants to respond effectively to the concomitant pressures of defending against herbivory and attracting pollinators.     

Patterns of growth,reproduction, defense,and herbivory in the dioecious shrub Baccharis halimifolia (Compositae)

Summary Patterns of growth, reproduction, defense (leaf resin) and herbivory were compared between the sexes of the dioecious shrub Baccharis halimifolia (Compositae). Male plants possessed longer shoots and more tender leaves, grew faster, and flowered and senesced earlier than female plants. Levels of leaf nitrogen, water content, and acetone-soluble resin (shown to deter feeding by polyphagous insect herbivores) did not differ between male and female plants. When offered a choice between leaves from male and female plants, adults of two leaf beetles (Chrysomelidae), the monophagous Trirhabda bacharidis and the polyphagous Paria thoracica, both preferred to feed on male leaves. Similarly, the daily fecundity of older females of T. bacharidis was higher when they were fed leaves from male compared to female plants. However, adult survivorship and total fecundity of T. baccharidis did not differ between male and female leaf treatments. We attribute the feeding preference for and slight increase in fecundity on male plants to the tenderness of male leaves. Larvae of the fly Tephritis subpura (Tephritidae) fed exclusively in the sterile receptacle of male flower heads (85% infested), but the phenology was such that pollen production was not adversely affected. Larvae of two other flies Dasineura sp. and Contarinia sp. (Cecidomyiidae) occupied >95% of only female flower heads where they fed among and on the developing seeds. We conclude that foliage-feeding herbivores are unlikely candidates to explain the female-biased sex ratio (59% female) of B. halimifolia plants in the field, and that their preference for male plants is a result of plant characteristics (e.g. rapid growth) that have been selected by some other factor. However, our data on selective floral herbivory in B. halimifolia are in accord with the argument that dioecy reduces the inadvertent loss of flower parts of one sex when herbivores feed on flower parts of the opposite sex.     

Effects of herbivore identity on plant fecundity

Herbivores are pervasive, yet their effects on plant fecundity are often variable. One potential source of variation in herbivore impacts results from differing feeding modes of herbivores. We examined the relative importance of inflorescence-feeding insects versus large ungulates in affecting the fecundity of Balsamorhiza sagittata (Asteraceae), a dominant native perennial forb in western Montana, USA. We quantified these effects across four sites that varied in elevation to determine how consistent herbivore impacts were across these divergent sites. Insect herbivores were present in flower heads at all sites but they significantly depressed plant fecundity at two of the four sites. At the two sites where herbivore suppression had significant effects, this treatment let to 1.6 and 3.4-fold increases in seed production, respectively. In contrast, across all sites ungulates had minimal impacts on balsamroot flower and seed production. Seed addition experiments revealed that at some sites and in some years B. sagittata is seed-limited, as there was a positive relationship between seed input and seedling recruitment. Thus, reductions in seed production from heavy insect herbivory may limit balsamroot recruitment in some locations. Overall, results show that inconspicuous insects have stronger effects on balsamroot fecundity than do mammalian herbivores, but the magnitude of negative impacts at both the individual and population-level vary by site.     

珍稀濒危植物距瓣尾囊草(Urophysa rochkii)的开花物候和繁育系统特性

通过野外观察,运用套袋授粉和联苯胺-过氧化氢法等实验方法对距瓣尾囊草开花物候以及种群的繁育系统特性进行研究。研究结果:1)距瓣尾囊草为两性花,聚伞状花序,花期较长,从头年12月持续到次年4月,单花花期持续8—15 d,种群花期可持续4个月左右。2)距瓣尾囊草在花朵未开放前花粉没有活力,花药开裂当天花粉活力达到94.8%,第2天为90.3%,第3天为81.6%,第4天为62.9%,此后其花粉活力明显减弱;柱头可授性于散粉后第3天开始出现,散粉后4—5天最强,散粉后第8天柱头失去可授性;柱头可授性和花粉活力有5 d左右的重叠期。3)其花粉胚珠比P/O为938.5±250,按照Cruden标准划分,其有性繁育系统为兼性异交。4)按照Dafni的标准,距瓣尾囊草的OCI=4,即繁育系统为异交、部分自交亲和、需要传粉者。5)人工异花授粉结实率达80%以上,略高于自然结实率78.94%;直接套袋结实率为5.71%;去雄套袋和去雌套袋均不结实。以上结果表明,距瓣尾囊草繁育系统表现为异交为主、部分自交亲和并且不存在无融合生殖现象,其开花物候、花部特征和繁育系统为适应特殊的环境提供了一定的生殖保障,本次研究结果为距瓣尾囊草的迁地保护和种群的繁衍复壮提供理论依据。     

巨伞钟报春繁殖策略随海拔梯度的变异

巨伞钟报春(Primula florindae)是报春花属(Primula)的一种二型花柱植物,为青藏高原地区特有种。该研究于巨伞钟报春自然种群在色季拉山的分布下限(3 100m)至上限(林线4 350m)沿海拔梯度设立5个远离人为活动干扰的样点,并选取开花物候、花部结构性状、传粉昆虫、性分配、自然结实5个繁殖表征性状,通过分析比较不同海拔梯度样点的繁殖表征性状之间的差异,明确巨伞钟报春繁殖性状对海拔变化的适应策略,并探讨未来气候变化对巨伞钟报春的分布格局可能产生的影响。研究发现:(1)巨伞钟报春始花时间最早为中海拔种群,其次是低海拔种群,最晚为高海拔种群,而且随海拔高度上升,巨伞钟报春两种表型的花寿命均显著延长;花部结构面积显著增大;访花昆虫种类减少;性分配倾向于偏雌分配,各性状对于不同海拔之间异质环境的适应可能是巨伞钟报春在各海拔繁殖策略上表现出差异的主要原因。(2)随着海拔的上升,巨伞钟报春的开花数显著减少,但虫食数与虫食率也显著降低,最终不同海拔有效座果数和结籽数均无显著差异,表明巨伞钟报春通过应对不同环境形成相应的繁殖策略,在不同海拔均能保证恒定的繁殖成功率,并维持种群的稳定。(3)气候变化将会对巨伞钟报春的分布产生深远影响,其分布下限可能发生上移,但更高海拔地区现有的砂壤环境不适于巨伞钟报春的生长,且传粉昆虫在气候变化综合作用下的时空变异尚不明确,致使其分布上限上移空间有限。研究推测,未来100年内,巨伞钟报春的分布下限可能上移至其现今分布格局的中海拔地区,造成其分布区域缩小。     

金沙江干热河谷滇榄仁开花物候与繁育系统

通过野外定点观测,并利用套袋实验、解剖实验以及花粉形态特征观察与活力检测、柱头可受性检测、花粉/胚珠比以及异交指数等,研究了金沙江干热河谷滇榄仁自然群体花部形态特征与开花进程、繁育系统特征以及传粉媒介与环境的适应性等内容。结果表明,滇榄仁始花期在每年4月上旬,群体花期持续时间为30d左右,开花同步性高,呈典型的"集中开花模式"。单花开放时,柱头先伸长和膨大,约4d后雄蕊伸出,具有雌雄异熟的特征,一定程度上避免了自交的发生。单花开放进程可划分为花蕾期、柱头伸长期、雄蕊始露期、盛开期、盛开后期、花谢期等6个时期。除了花蕾期外,整个开花期的花粉均具有活力。花粉活力与柱头可受性之间避开了最适授粉期,但也有部分重叠。滇榄仁可能同时具有风媒和虫媒传粉。繁育系统以异交为主,部分自交亲和,需要传粉者。滇榄仁花部特征、开花物候和繁育系统为其适应干热河谷恶劣气候环境提供了一定的生殖保障和进化潜力。良好的群落环境有助于促进滇榄仁异花传粉,产生更多有效的种子,从而促进林下自然更新。     

Effects of floral herbivory, limited pollination, and intrinsic plant characteristics on phenotypic gender in Sanicula arctopoides

Sexual expression in hermaphroditic plants is often a function of environmental factors affecting individuals before or during flowering. I tested for the effects of floral herbivory and lack of pollination in early umbels on the relative proportions of hermaphroditic and staminate (male) flowers produced on later umbels by Sanicula arctopoides, a monocarpic, andromonoecious perennial. Neither floral herbivory or lack of early pollination had a significant effect on the ratio of the two floral morphs, but the probability of producing staminate flowers on late umbels was strongly and positively related to plant size measured just prior to floral initiation and prior to herbivory. Plant size was also negatively correlated with flowering date. I suggest that producing staminate flowers on late umbels should benefit large early-blooming plants more than small late-blooming plants because more mating opportunities occur during the period when these flowers release pollen. Although herbivory did not cause labile changes of sex, whole plant phenotypic gender was still strongly affected by various forms of treatment. Sex-biased herbivory or lack of pollination rendered plants more or less phenotypically male, depending on which tissues were affected. Deer and pollen-feeding mites preferentially remove male tissues while hymenopteran seed predators preferentially remove female tissues. I conclude that combinations of herbivores could have counteracting or compounding effects on plant gender, and these effects may change the rankings of male and female reproductive success within populations. Received: 20 February 1996/Accepted: 30 July 1996     

Large differences in the composition of herbivore communities and seed damage in diploid and autotetraploid plant species

Herbivory is one of the key interactions affecting plant fitness. Despite the large amount of data available on the effects of herbivores on various plant groups, we still know very little information about the interactions of herbivores with individuals having different ploidy levels. We studied the relationship of diploid and tetraploid Centaurea phrygia in natural and experimental garden conditions to the community of pre‐dispersal seed predators developing in flower heads of the plants. In addition, we collected a set of data on flowering phenology, and flower head morphology and chemistry to investigate potential mechanisms underlying the differences between cytotypes. The two cytotypes are strongly differentiated in their flower head morphology and chemistry as well as in their flowering phenology, with flower heads of diploids being larger, containing more secondary metabolites and flowering later. Also, the two cytotypes strongly differed in the composition of insect communities in the flower heads and tetraploids suffered higher seed damage than the diploids. The differences between cytotypes in seed damage were generally consistent across datasets, indicating that the differences are not due to differences in the habitats in which the cytotypes occur but are due to differences in particular biological characteristics of the plants. The diversity and composition of insect communities, however, strongly varied between years and environments. Flowering phenology could explain part, but not all of the differences observed between cytotypes, indicating that other factors such as flower head morphology or chemistry could also play a role. The study indicated that the differences between the two cytotypes are important determinant of the plant–herbivore interactions in the system. Although we identified multiple factors that could explain the different associations, further research is needed to assess the relative importance of each of these factors. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115 , 270–287.