Factors affecting fruit and seed production of Paeonia ostii “Feng Dan”, an economically important oil tree

Many factors may affect reproduction of animal-pollinated species. In this study, the effects of pollen limitation, attractive traits (flower number, plant height and flower width) and flowering phenological traits (flowering onset, duration and synchrony) on female reproduction, as well as the patterns of variation in fruit and seed production within plants, were investigated in Paeonia ostii “Feng Dan” over two flowering seasons (2018 and 2019). Fruit set was very high (90%), and pollen supplementation did not increase fruit and seed production in either year, indicating no pollen limitation. Fruit set, ovule number per fruit and mean individual seed weight per fruit were not affected by any of the six attractive and phenological traits in either year, whereas seed number per fruit was related to the three attractive traits in one or both years. Seed number per plant was positively affected by the three attractive traits and best explained by flower number in both years, but the effect of each of the three phenological traits on seed number per plant differed between years. Within plants, the fruit set, ovule number, seed set and seed number per fruit declined from early- to late-opening flowers, presumably because of resource preemption, but the mean individual seed weight did not vary across the flowering sequence. Our study shows that attractive traits of Paeonia ostii “Feng Dan” are more important than flowering phenological traits in the prediction of total seed production per plant.     

The effect of segregation of flowering time on fine-scale spatial genetic structure in an alpine-snowbed herb Primula cuneifolia

The flowering phenology of alpine-snowbed plants varies widely depending on the time of snowmelt. This variation may cause spatial and temporal heterogeneity in pollen dispersal, which in turn may influence genetic structure. We used spatial autocorrelation analyses to evaluate relative effect of segregation in flowering time and physical distance on fine-scale spatial genetic structure (SGS) of a snowbed herb Primula cuneifolia sampled in 10-m grids within a continuous snow patch (110 x 250 m) using nine allozyme loci. Although the individual flower lasts for 相似文献   

Refuse attracts? Effect of refuse dumps of leaf‐cutting ants on floral traits

The nutrient‐rich organic waste generated by ants may affect plant reproductive success directly by enhancing fruit production but also indirectly, by affecting floral traits related with pollinator attraction. Understanding how these soil‐nutrient hot spots influence floral phenotype is relevant to plant–pollination interactions. We experimentally evaluated whether the addition of organic waste from refuse dumps of the leaf‐cutting ant Acromyrmex lobicornis (Hymenoptera: Formicidae: Attini) alters floral traits associated with pollinator attraction in Eschscholzia californica (Ranunculales: Papaveraceae), an entomophilous herb. We analysed flower shape and size using geometric morphometric techniques in plants with and without the addition of refuse‐dumps soil, under greenhouse conditions. We also measured the duration of flowering season, days with new flowers, flower production and floral display size. Plants growing in refuse‐dumps soil showed higher flower shape diversity than those in control soil. Moreover, plants in refuse‐dumps soil showed bigger flower and floral display size, longer flowering season, higher number of flowering days and flower production. As all these variables may potentially increase pollinator visits, plants in refuse‐dumps soil might increase their fitness through enhanced attraction. Our work describes how organic waste from ant nests may enhance floral traits involved in floral attraction, illustrating a novel way of how ants may indirectly benefit plants.     

31种木本植物开花物候与系统发育的关系

植物物候通常被认为是由环境因素,如降水、温度和日照长度所决定,然而环境因素是否是物候唯一的决定因素仍然存在很大争议。谱系结构表征了植物在进化上的顺序,该发育时序是否对物候产生影响,当前仍然未知。在调查2016年春季新疆乌鲁木齐市最常见的31种木本植物的初始开花时间、败花时间和开花持续时间的基础上,通过分析植物开花物候的分布特征、开花物候在乔灌木间的差别、以及植物谱系距离与开花物候距离间的关系,试图揭示植物的开花物候和物种谱系(进化)顺序间的关系。结果表明:(1)新疆乌鲁木齐市31种木本植物的初始开花时间为4月18日±9d、败花时间为5月5日±12d、开花持续时间为(16±8)d;(2)乔木的初始开花时间和败花时间的标准差分别均低于灌木,乔木开花物候相对灌木更稳定;(3)乔木的初始开花和败花时间均显著早于灌木(P0.05),但开花持续时间在两者间未有显著性差异(P0.05);(3)31种木本植物间的初始开花时间距离、败花时间距离和开花持续时间距离均与物种谱系距离存在显著线性回归关系(P0.05)。综上可知:乔灌木在垂直空间上的分化使得木本植物的开花物候在植物生活型间存在不同。对植物的开花物候,除已被证明的降水、温度和日照长度等环境因素的影响外,物种进化顺序也可能造成了它在植物种间、时间和空间上的变异。     

Genetic variation in the reduction of attractive floral traits of an annual tarweed in response to drought and apical damage

Aims Foliar herbivory and water stress may affect floral traits attractive to pollinators. Plant genotypes may differ in their responses to the interplay between these factors, and evolution of phenotypic plasticity could be expected, particularly in heterogeneous environments. We aimed at evaluating the effects of simulated herbivory and experimental drought on floral traits attractive to pollinators in genetic families of the annual tarweed Madia sativa, which inhabits heterogeneous environments in terms of water availability, herbivore abundance and pollinator abundance.Methods In a greenhouse experiment with 15 inbred lines from a M. sativa population located in central Chile (Mediterranean-type climate), we measured the effects of apical bud damage and reduced water availability on: number of ray florets per flower head, length of ray florets, flower head diameter, number of open flower heads per plant, flowering plant height and flowering time.Important findings Apical damage and water shortage reduced phenotypic expression of floral traits attractive to pollinators via additive and non-additive effects. Plants in low water showed decreased height and had fewer and shorter ray florets, and fewer and smaller flower heads. Damaged plants showed delayed flowering, were less tall, and showed shorter ray florets and smaller flower heads. The number of ray florets was reduced by damage only in the low water treatment. Plant height, flowering time and number of flower heads showed among-family variation. These traits also showed genetic variation for plasticity to water availability. Ray floret length, flower head size and time to flowering showed genetic variation for plastic responses to apical damage. Plasticity in flowering time may allow M. sativa to adjust to the increased aridity foreseen for its habitat. Because genetic variation for plastic responses was detected, conditions are given for evolutionary responses to selective forces acting on plastic traits. We suggest that the evolution of adaptive floral plasticity in M. sativa in this ecological scenario (heterogeneous environments) would result from selective forces that include not only pollinators but also resource availability and herbivore damage.     

A phylogenetic comparative study of flowering phenology along an elevational gradient in the Canadian subarctic

Climate change is affecting high-altitude and high-latitude communities in significant ways. In the short growing season of subarctic habitats, it is essential that the timing and duration of phenological phases match favorable environmental conditions. We explored the time of the first appearance of flowers (first flowering day, FFD) and flowering duration across subarctic species composing different communities, from boreal forest to tundra, along an elevational gradient (600–800 m). The study was conducted on Mount Irony (856 m), North-East Canada (54°90′N, 67°16′W) during summer 2012. First, we quantified phylogenetic signal in FFD at different spatial scales. Second, we used phylogenetic comparative methods to explore the relationship between FFD, flowering duration, and elevation. We found that the phylogenetic signal for FFD was stronger at finer spatial scales and at lower elevations, indicating that closely related species tend to flower at similar times when the local environment is less harsh. The comparatively weaker phylogenetic signal at higher elevation may be indicative of convergent evolution for FFD. Flowering duration was correlated significantly with mean FFD, with later-flowering species having a longer flowering duration, but only at the lowest elevation. Our results indicate significant evolutionary conservatism in responses to phenological cues, but high phenotypic plasticity in flowering times. We suggest that phylogenetic relationships should be considered in the search for predictions and drivers of flowering time in comparative analyses, because species cannot be considered as statistically independent. Further, phenological drivers should be measured at spatial scales such that variation in flowering matches variation in environment.     

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.     

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.     

Floral plasticity: Herbivore‐species‐specific‐induced changes in flower traits with contrasting effects on pollinator visitation

Plant phenotypic plasticity in response to antagonists can affect other community members such as mutualists, conferring potential ecological costs associated with inducible plant defence. For flowering plants, induction of defences to deal with herbivores can lead to disruption of plant–pollinator interactions. Current knowledge on the full extent of herbivore‐induced changes in flower traits is limited, and we know little about specificity of induction of flower traits and specificity of effect on flower visitors. We exposed flowering Brassica nigra plants to six insect herbivore species and recorded changes in flower traits (flower abundance, morphology, colour, volatile emission, nectar quantity, and pollen quantity and size) and the behaviour of two pollinating insects. Our results show that herbivory can affect multiple flower traits and pollinator behaviour. Most plastic floral traits were flower morphology, colour, the composition of the volatile blend, and nectar production. Herbivore‐induced changes in flower traits resulted in positive, negative, or neutral effects on pollinator behaviour. Effects on flower traits and pollinator behaviour were herbivore species‐specific. Flowers show extensive plasticity in response to antagonist herbivores, with contrasting effects on mutualist pollinators. Antagonists can potentially act as agents of selection on flower traits and plant reproduction via plant‐mediated interactions with mutualists.     

The strength of assortative mating for flowering date and its basis in individual variation in flowering schedule

Although it has been widely asserted that plants mate assortatively by flowering time, there is virtually no published information on the strength or causes of phenological assortment in natural populations. When strong, assortative mating can accelerate the evolution of plant reproductive phenology through its inflationary effect on genetic variance. We estimated potential assortative mating for flowering date in 31 old‐field species in Ontario, Canada. For each species, we constructed a matrix of pairwise mating probabilities from the individual flowering schedules, that is the number of flower deployed on successive dates. The matrix was used to estimate the phenotypic correlation between mates, ρ, for flowering date. We also developed a measure of flowering synchrony within species, S, based upon the eigenstructure of the mating matrix. The mean correlation between pollen recipients and potential donors for flowering date was  = 0.31 (range: 0.05–0.63). A strong potential for assortative mating was found among species with high variance in flowering date, flowering schedules of short duration and skew towards early flower deployment. Flowering synchrony, S, was negatively correlated with potential assortment (r = ?0.49), but we go on to show that although low synchrony is a necessary condition for phenological assortative mating, it may not be sufficient to induce assortment for a given phenological trait. The potential correlation between mates showed no seasonal trend; thus, as climate change imposes selection on phenology through longer growing seasons, spring‐flowering species are no more likely to experience an accelerated evolutionary response than summer species.     

西双版纳地区鞘花的繁殖物候特征及影响因素

桑寄生植物作为关键种和关键性食物资源在生态系统中扮演着重要角色,其鞘花的繁殖物候特征不仅会影响自身的繁殖适合度而且还会影响依赖于其获取食物资源的动物。为了解鞘花的繁殖物候特征及其影响因素,探究其与寄主植物和种子散布者之间的相互作用关系。该研究以西双版纳地区分布的鞘花为对象,通过定期观测鞘花和其寄主植物木荷的繁殖物候,测量它们的生物学特性和温湿度等环境因子,并分析鞘花在个体水平和种群水平上的繁殖物候特征以及寄主植物和温湿度对其繁殖物候的影响。结果表明:(1)鞘花的开花物候属于集中大量开花模式,整个种群的花期和果期的持续时间分别约为20 d和72 d,花期和果期的同步性指数都较高,6月中旬鞘花果实被取食的数量和速率最大,之后逐渐降低。(2)鞘花的始花期与木荷的始花期相关性较高,花期和果期与木荷的繁殖物候基本重叠。(3)每月开花和果熟的个体数量与同期和前一个月的平均温度和相对湿度的相关关系均不显著。总之,桑寄生植物的繁殖物候特征可能受到较多因素的影响,若想全面了解半寄生植物的繁殖物候特征,就要综合考虑生物和非生物等多种因子的共同作用。     

Network robustness and structure depend on the phenological characteristics of plants and pollinators

Many structural patterns have been found to be important for the stability and robustness of mutualistic plant–pollinator networks. These structural patterns are impacted by a suite of variables, including species traits, species abundances, their spatial configuration, and their phylogenetic history. Here, we consider a specific trait: phenology, or the timing of life history events. We expect that timing and duration of activity of pollinators, or of flowering in plants, could greatly affect the species'' roles within networks in which they are embedded. Using plant–pollinator networks from 33 sites in southern British Columbia, Canada, we asked (a) how phenological species traits, specifically timing of first appearance in the network and duration of activity in a network, were related to species'' roles within a network, and (b) how those traits affected network robustness to phenologically biased species loss. We found that long duration of activity increased connection within modules for both pollinators and plants and among modules for plants. We also found that date of first appearance was positively related to interaction strength asymmetry in plants but negatively related to pollinators. Networks were generally more robust to the loss of pollinators than plants, and robustness increased if the models allow new interactions to form when old ones are lost, constrained by overlapping phenology of plants and pollinators. Robustness declined with the loss of late‐flowering plants, which tended to have higher interaction strength asymmetry. In addition, robustness declined with loss of early‐flying or long‐duration pollinators. These pollinators tended to be among‐module connectors. Our results point to networks being limited by early‐flying pollinators. If plants flower earlier due to climate change, plant fitness may decline as they will depend on early emerging pollinators, unless pollinators also emerge earlier.     

Heritabilities of lateral and vertical herkogamy in Lysimachia arvensis

Herkogamy, spatial separation between stigma and anthers within a flower, is important in regulating plant-mating systems. We studied phenotypic variation and heritability of herkogamy traits in Lysimachia arvensis (=Anagallis arvensis) that show both lateral and vertical herkogamy in the same flower, a rare strategy in flowering plants. Both lateral and vertical herkogamy showed continuous variation in 15 natural populations. Lateral herkogamy, measured as the angle between style and stamens, ranged from 5.6 to 66.5°; vertical herkogamy ranged from reverse to approach herkogamy. Herkogamy traits were constant within plants but variable among plants and populations. Flowers with marked lateral herkogamy showed mainly reverse herkogamy, whereas flowers with low lateral herkogamy showed mainly approach herkogamy. Both herkogamy traits showed a high degree of narrow sense heritability (h² = 0.843 for lateral and h² = 0.635 for vertical herkogamy). We discuss the possibility that variation in both herkogamy traits among populations of L. arvensis is a consequence of differential selective pressures under different pollination environments.     

Seedlings and ramets recruitment in two rhizomatous species of Rupestrian grasslands: Leiothrix curvifolia var. lanuginosa and Leiothrix crassifolia (Eriocaulaceae)

Leiothrix curvifolia var. lanuginosa and Leiothrix crassifolia are endemic and sympatric species in the Brazilian rupestrian grasslands, a habitat that has a predominance of sandy and shallow soils with low water retention. Based on the premise that soil moisture is one of the abiotic factors that affects most reproduction in plants, we hypothesized that the flowering phenology events and establishment of sexual and vegetative offspring would occur in the periods of higher soil water availability. We marked 478 ramets distributed among 100 genets of L. curvifolia var. lanuginosa and 693 ramets distributed among 100 genets of L. crassifolia, so that they could be observed monthly along the two rainy seasons from December 2003 to 2004. Both species showed phenological synchrony in the flower heads and seedlings production with soil moisture availability. Seedling mortality was intense in the dry period. Unlike the seedlings, the ramets survived was 100%. The greater capacity of ramets to survive can result from a much greater biomass compared with seedlings, and ramets become adult much faster. We conclude that for a successful seedling establishment, the synchronization with the rainy season was required, and moreover, that repeated seedling recruitment can be important for the maintenance of local populations of these species which suffer from high seedling mortality in the drought period. It is likely that the coincidence of the rainy period with seedling establishment is an important factor that determines the flowering phenological pattern of L. curvifolia var. lanuginosa and L. crassifolia in rupestrian grasslands.     

Developmental instability in Brassica campestris (Cruciferae): fluctuating asymmetry of foliar and floral traits

The degree of fluctuating asymmetry of bilateral traits provides a measure of developmental instability, which can be influenced by genetic as well as environmental stress. We studied genetic variation between and within two populations of the mustard Brassica campestris for asymmetry of foliar (cotyledon width) and floral (petal length and width) traits as well as for phenological (germination and flowering) and performance (biomass and flowering) traits. The two populations differed in mean expression of most traits, including asymmetry. However, within-population estimates of genetic variability tended to be lower for asymmetry than other traits. Asymmetry was greater in the population that had lower biomass accumulation and flower production, which supports the idea that population-level asymmetry may be indicative of population-level performance. However, within each population, evidence that performance was negatively correlated with asymmetry was equivocal. Within populations there was little or no concordance among estimates of asymmetry based on different structures, i.e., plants that had highly asymmetrical cotyledons did not tend to have highly asymmetrical petals. The lack of a general buffering capacity at the individual level may be explained by developmental processes (e.g., action of different genes or morphogens) as well as evolutionary processes (e.g., selection on asymmetry of different traits).     

Statistical downscaling of monthly mean air temperature to the beginning of flowering of Galanthus nivalis L. in Northern Germany

 We have examined the relationship between phenological data and concurrent large-scale meterological data. As phenological data we have chosen the beginning of the flowering of Galanthus nivalis L. (flowering date) in Northern Germany, and as large-scale meteorological data we use monthly mean near-surface air temperatures for January, February and March. By means of canonical correlation analysis (CCA), a strong linear correlation between both sets of variables is identified. Twenty years of observed data are used to build the statistical model. To validate the derived relationship, the flowering date is downscaled from air temperature observations of an independent period. The statistical model is found to reproduce the observed flowering dates well, both in terms of variability as well as amplitude. Air temperature data from a general circulation model of climate change are used to estimate the flowering date in the case of increasing atmospheric carbon dioxide concentration. We found that at a time of doubled CO₂ concentration (expected by about 2035) G. nivalis L. in Northern Germany will flower ∼2 weeks and at the time of tripled CO₂ concentration (expected by about 2085) ∼4 weeks earlier than presently. Received: 7 August 1996 / Accepted: 27 November 1996     

Reproductive success in varying light environments: direct and indirect effects of light on plants and pollinators

Plant populations often exist in spatially heterogeneous environments. Light level can directly affect plant reproductive success through resource availability or by altering pollinator behavior. It can also indirectly influence reproductive success by determining floral display size which may in turn influence pollinator attraction. We evaluated direct and indirect effects of light availability and measured phenotypic selection on phenological traits that may enhance pollen receipt in the insect-pollinated herb Campanulastrum americanum. In a natural population, plants in the sun had larger displays and received 7 times more visits than plants in the shade. Using experimental arrays to separate the direct effects of irradiance on insects from their response to display size, we found more visits to plants in the sun than in the shade, but no association between number of visits each flower received and display size. Plants in the sun were not pollen limited but pollen-augmented shade flowers produced 50% more seeds than open-pollinated flowers. Phenological traits, which may influence pollen receipt, were not under direct selection in the sun. However, earlier initiation and a longer duration of flowering were favored in the shade, which may enhance visitation in this pollen-limited habitat.     

迁地保育植物花期物候对迁入地气候变化的响应

以中国科学院武汉植物园内栽培的长果秤锤树(Sinojackia dolichocarpa C. J. Qi)、山白树(Sinowilsonia henryi Hemsl.)、夏腊梅(Sinocalycanthus chinensis Cheng et S. Y. Chang)、紫茎(Stewartia sinensis Rehd. et Wils.)和绒毛皂荚(Gleditsia vestita Chun et How ex B. G. Li) 5种迁地保育植物为对象,通过2008-2016年观察记录的初花期物候及整个花期长度的数据,研究花期的年际变化规律及其与迁入地武汉气候因子的相关性。结果显示:(1)从初花期来看,长果秤锤树的初花期每年提前1.25 d,紫茎的初花期每年推迟1.35 d,绒毛皂荚的初花期每年推迟1.22 d。(2)从花期长度来看,山白树的花期每年增加1.72 d,夏蜡梅的花期每年减少1.62 d,紫茎的花期每年增加0.32 d。(3)从花期与气候因子的相关性来看,年降水量、年平均相对湿度、 10℃有效积温、花前 10℃的有效积温是影响这5种植物初花期、花期长度的主要气候因子;不同物种间影响花期的主要气候因子有所差异。     

金城山柔毛淫羊藿的开花物候与生殖特性

采用实地观测的方法,对南充市金城山三个不同生境中柔毛淫羊藿的开花物候特征及其生殖特性进行了研究。结果表明:柔毛淫羊藿花期为3月上旬至4月上旬,其种群、个体、花序和单花的花期分别历时30~41、22~34、9~18和4~8 d。三个生境中柔毛淫羊藿种群的开花物候进程基本相同,均呈单峰集中开花式样,因而能够吸引更多的传粉者访问而达到生殖成功。开花物候指数与坐果数之间的相关分析结果表明,坐果数与始花日期存在显著的负相关关系,与花期持续时间和开花数均呈极显著的正相关关系。揭示了药用植物柔毛淫羊藿的开花物候特征与生殖特性。     

Fire effects on plant reproductive fitness vary among individuals,reflecting pollination-dependent mechanisms

Premise

Fire induces flowering in many plant species worldwide, potentially improving reproductive fitness via greater availability of resources, as evident by flowering effort, and improved pollination outcomes, as evident by seed set. Postfire increases in flowering synchrony, and thus mating opportunities, may improve pollination. However, few studies evaluate fire effects on multiple components of fitness. Consequently, the magnitude and mechanism of fire effects on reproductive fitness remain unclear.

Methods

Over multiple years and prescribed burns in a prairie preserve, we counted flowering stems, flowers, fruits, and seeds of three prairie perennials, Echinacea angustifolia, Liatris aspera, and Solidago speciosa. We used aster life-history models to assess how fire and mating opportunities influenced annual maternal fitness and its components in individual plants.

Results

In Echinacea and Liatris, but not in Solidago, fire increased head counts, and both fire and mating opportunities increased maternal fitness. Burned Echinacea and Liatris plants with many flower heads produced many seeds despite low seed set (fertilization rates). In contrast, plants with an average number of flower heads had high seed set and produced many seeds only when mating opportunities were abundant.

Conclusions

Fire increased annual reproductive fitness via resource- and pollination-dependent mechanisms in Echinacea and Liatris but did not affect Solidago fitness. The consistent relationship between synchrony and seed set implies that temporal mating opportunities play an important role in pollination. While fire promotes flowering in many plant species, our results reveal that even closely related species exhibit differential responses to fire, which could impact the broader plant community.