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1.
Yoko Nishikawa 《Plant Ecology》2009,202(2):337-347
I studied the relationship between seed-set patterns within inflorescences and temporal variations in light and pollinator
availabilities for 2 years in the spring ephemeral species Gagea lutea in a deciduous forest. Timing of canopy closure and seasonal trend of pollinator frequency did not synchronize with the annual
fluctuation in flowering phenology. In the early snowmelt year, seed-set success reflected the seasonal pollinator abundance
from early to middle flowering periods. In the late snowmelt year, however, seed-set rates were independent of pollinator
activity and decreased with canopy closing even after hand pollination. The restricted seed production by defoliation and
the increase in seed-set rates at the forest edge suggested that seed production was supported by current photosynthetic carbon
gain. Thus, annual fluctuations of reproductive success can explain the variation in flowering phenology within a population
although seasonal light deterioration would serve as a selective force for flowering in the early season. 相似文献
2.
McCall AC 《Oecologia》2008,155(4):729-737
While herbivory has traditionally been studied as damage to leaves, florivory – herbivory to flowers prior to seed set – can
also have large effects on plant fitness. Florivory can decrease fitness directly, either through the destruction of gametes
or through alterations to plant physiology during fruit set, and can also change the appearance of a flower, deterring pollinators
and reducing seed set. In order to distinguish between these hypotheses, it is necessary to both damage flowers and add pollen
in excess to study the effects of damage on pollen limitation. Very few studies have used this technique over the lifetime
of a plant. Here I describe a series of experiments showing the effects of natural and artificial damage on reproductive success
in the annual plant Nemophila menziesii (Hydrophyllaceae, sensu lato). I show that natural and artificial petal damage decreased radial symmetry relative to controls
and that both types of damage deterred pollinator activity. Both naturally damaged flowers and artificially damaged flowers
in the field set fewer fruit or seed relative to undamaged control flowers. Finally, in an experiment crossing artificial
petal damage with pollen addition, petal damage alone over the lifetime of this plant decreased female fitness, but only after
a threshold of damage was reached. The fitness effect appeared to be direct because there was no detectable effect of pollen
addition on the relationship between florivory and fitness. This result implies that both damaged and undamaged plants show
similar amounts of pollen limitation and suggests that pollinator-mediated effects contributed little to the negative effects
of florivory on female fitness. Florivores may thus be an under-appreciated agent of selection in certain plants, although
more experimental manipulation of florivory is needed to determine if it is important over a range of taxa. 相似文献
3.
Few studies of plant–pollinator interactions in fragmented landscapes evaluate the consequences of floral visitor variation
on multiple stages of plant reproduction. Given that fragmentation potentially has positive or negative effects on different
organisms, and that self-incompatible plant species depend on pollinators for sexual reproduction, differences in floral visitor
assemblages may affect certain plant reproductive stages. We evaluated how pollinator assemblage, availability of floral resources,
pollination, reproductive output, and seed and seedling performance of Psychotria suterella Muell. Arg. varied among three fragmentation categories: non-fragmented habitats, fragments connected by corridors, and isolated
fragments. Richness and frequency of floral visitors were greater in fragments than in non-fragmented sites, resulting mainly
from the addition of species typically found in disturbed areas. Although 24 species visited Psychotria suterella flowers, bumblebees were considered the most important pollinators, because they showed the highest frequency of visits and
were present in eight out of ten sites. Additionally, the number of pollen tubes per flower per visit was lower in areas without
bumblebees. The increased visitation in fragments seemed to enhance pollination slightly. However, fruit and seed output,
germination, and seed and seedling mass were similar in non-fragmented sites, connected sites, and isolated fragments. Our
results suggested that, even for a self-incompatible species, responses to habitat fragmentation at different stages of plant
reproduction might be decoupled from the responses observed in floral visitors, if fruit set is not pollen limited. If all
reproductive stages were considered, variation on the small scale was more important than the variation explained by fragmentation
category. In spite of its self-incompatible breeding system, this plant–pollinator system showed resilience to habitat fragmentation,
mainly as a result of high availability of potential mates to P. suterella individuals, absence of pollen limitation, and the presence of bumblebees (Bombus spp.) throughout this highly connected landscape. 相似文献
4.
Plant reproduction can be strongly affected by herbivory and different features of pollination ecology, such as pollinator visitation rates and capacity for self-pollination. The purpose of this study is to compare the relative impact of herbivory and pollination on maternal reproductive success in endemic Aquilegia viscosa and its widespread congener Aquilegia vulgaris. We conducted herbivore exclusion experiments in two populations of each species in 2 different years and showed that the maternal fertility of A. viscosa was significantly more limited by floral predation and pre-dispersal seed predation than its widespread congener. In the absence of herbivory, A. viscosa retained significantly lower maternal fertility than A. vulgaris. Experimental pollinations in an insect-free glasshouse showed that the two species have an equal seed/ovule ratio both in the absence of pollinators and in the presence of non-limiting outcross pollination. Pollinator visitation rates were significantly higher in populations of A. vulgaris than in populations of A. viscosa. In addition, path analyses showed that spur length, an important trait for pollinator attraction in Aquilegia, and, indirectly sepal and petal width, contribute positively to the seed/ovule ratio in A. vulgaris, but not in A. viscosa. These results indicate that maternal fertility of endemic A. viscosa is strongly reduced by flower and seed predation despite low rates of pollinator visitation, and that pollen or resource limitation in the wild may further reduce maternal fertility. Finally, floral trait variation appears to be decoupled from fertility variation in endemic A. viscosa, which possibly constrains the evolution of reproductive traits in this species. 相似文献
5.
This study examines anthropogenic impacts on the pollination ecology of Sabatia kennedyana Fern. (Gentianaceae), a protandrous, insect-pollinated species at risk. Pollination processes were explored in disturbed
and non-disturbed sites in both high and low density patches on each of three lakes in southwest Nova Scotia, Canada. The
primary pollinators were Syrphid flies (Diptera: Syrphidae) and Halictid bees (Hymenoptera: Halictidae). Pollinator diversity
was not significantly different among lakes or sites. High flowering density plots were visited significantly more frequently
than low density plots in all site types; pollination rates and handling time were significantly lower in disturbed compared
to non-disturbed sites, such that pollinators both visited and spent less time handling flowers in disturbed sites. The reproductive
success of open-pollinated flowers was significantly different among lakes; there was also a disturbance by lake interaction
with higher reproductive success on disturbed sites in two of the lakes. Thus, this study finds evidence of reduced pollination
service together with a beneficial reproductive effect of disturbance. The significance of these results and the possibility
that the spatial genetic structure of disturbed sites is reduced are discussed. We conclude that reduced pollination service
and changes in the genetic structure of populations demonstrate the potentially negative impact of human associated activities
on pollinator activity and plant reproductive strategy. 相似文献
6.
Resource and pollen limitation, as well as pollen/ovule incompatibility, have been proposed as causes to explain fruit abortion.
To assess whether abortion in Opuntia microdasys was due to resource and/or pollen limitation and could therefore be reversed fruit set and seed set were studied using controlled
pollination experiments on 60 plants that had been randomly assigned a combination of watering and fertilization treatments.
On the other hand, to test whether fruit abortion was irreversible, due to pollen/ovule incompatibility, we examined the reproductive
biology of the species. This included observations on floral phenology, nectar production, flower visitors, numbers of pollen
grains and ovules, and self-pollination experiments. Results showed that O. microdasys is a fully self-incompatible species and its floral biology and the activity of the main pollinator allow constant deposition
of incompatible pollen onto stigmas, which may contribute to fruit abortion. Reproductive success was limited by nutrients
and pollen, but the fruit set increased only by 58%, compared to 47% of the control, after the experimental addition of pollen,
nutrients and water. The magnitude of pollen and resource limitation suggests that similar levels of abortion will be present
in good as well as in bad years. Selfing as well as incompatibility between ramets from the same clone and between closely
related plants seem plausible candidates to explain the large proportion of fruit abortion, and experimental cross pollination
between genotypes identified through molecular markers are necessary to fully understand the considerable abortion rate that
remains unexplained after pollen and resource addition. Interestingly, the possible reason why the abortion of energetically
expensive fruits has not been eliminated by natural selection is that the aborted fruits are propagules able to root and produce
new plants with the same genotype of the mother. Abortion would have a dramatic effect on cross-fertilized genotypes because
they result in zero fitness, but it would have a positive effect on the fitness of the maternal genotype because a clonal
offspring is produced. Evidently, the exact fitness consequences to the maternal plant will depend on the differences in survival
and reproduction of these different offspring types. 相似文献
7.
The availability of soil and pollination resources are main determinants of fitness in many flowering plants, but the degree
to which each is limiting and how they interact to affect plant fitness is unknown for many species. We performed resource
(water and nutrients) and pollination (open and supplemental) treatments on two species of flowering plants, Ipomopsis aggregata and Linum lewisii, that differed in life-history, and we measured how resource addition affected floral characters, pollination, and reproduction
(both male and female function). We separated the direct effects of resources versus indirect effects on female function via
changes in pollination using a factorial experiment and path analysis. Resource addition affected I. aggregata and L. lewisii differently. Ipomopsis aggregata, a monocarp, responded to fertilization in the year of treatment application, increasing flower production, bloom duration,
corolla width, nectar production, aboveground biomass, and pollen receipt relative to control plants. Fertilization also increased
total seed production per plant, and hand-pollination increased seeds per fruit in I. aggregata, indicating some degree of pollen limitation of seed production. In contrast, fertilization had no effect on growth or reproductive
output in the year of treatment on L. lewisii, a perennial, except that fertilization lengthened bloom duration. However, delayed effects of fertilization were seen in
the year following treatment, with fertilized plants having greater aboveground biomass, seeds per fruit, and seeds per plant
than control plants. In both species, there were no effects of resource addition on male function, and the direct effects
of fertilization on female function were relatively stronger than the indirect effects via changes in pollination. Although
we studied only two plant species, our results suggest that life-history traits may play an important role in determining
the reproductive responses of plants to soil nutrient and pollen additions. 相似文献
8.
Carol K. Augspurger 《Plant Ecology》2011,212(7):1193-1203
Frost damage and re-foliation are seldom quantified for forest species, but are of ecological and evolutionary importance.
This study of Aesculus glabra (Ohio buckeye) in a deciduous forest remnant in Illinois, USA, quantified frost damage to leaves and flowers after sub-freezing
temperatures in April 2007. It also documented re-foliation and later growth, reproduction, and survival in 2007–2009 for
the 355 study individuals of four life stages growing 0–200 m from the forest edge. Life stages differed in % leaf damage
because of differences in phenology during the frost. Large saplings with fully expanded, immature leaves had higher % damage
and lower % canopy fullness after re-foliation than smaller saplings with partially or fully mature leaves and canopy trees
undergoing shoot expansion with folded leaflets. Percent damage increased for saplings closer to edges. Large saplings with
heavier frost damage to leaves had partial re-foliation in deep shade, lower % canopy fullness, earlier senescence, a shorter
growing season, and greater death of next year’s buds. By 2008, large saplings with greater damage in 2007 had more dead branches
and lower % canopy fullness. By 2009, 11% of large saplings had died. In 2007, frost damaged no flowers, but final fruit crop
size was negatively related to % leaf damage. Edge trees with total leaf damage aborted all fruits. The frost event differentially
affected individuals in their length and time of growing season, energy budget, and, ultimately, reproduction, and survival.
The population’s local-scale demography and spatial pattern also changed as large saplings died. 相似文献
9.
Naufraga balearica is an endemic umbelliferous plant of Mallorca (Balearic Islands, Spain), considered Critically Endangered according IUCN
categories. We present a study of its reproductive biology to look for the causes of its threatened status. It was carried
out in natural populations at Cap de Catalunya and Coves Blanques and in ex-situ cultivated plants on the campus of the Universitat
de les Illes Balears. We examined (1) the flowering and fruiting phenology, reproductive potential and reproductive success;
(2) the pollen/ovule (P/O) ratio and mating system; (3) the identities and numbers of pollinators; (4) the germination potential
and the effect of temperature on the germination process; and (5) the seedling performance of this species. The results indicated
that under natural conditions, an average individual produced approximately 100 seeds and cross-pollination was the most effective
mating system. Pollination was myrmecophilous, and the germination potential was high (76–97%), but seedling survival after
the first summer was low (7–54%). We conclude that the major threats to this species are fundamentally extrinsic in character
and are related to changing climatic conditions, soil erosion and alteration, and umbel predation. Given that cross-pollination
yields greater reproductive success and that pollination is myrmecophilous, lower population densities would lead to lower
reproductive success for the species. Therefore, conservation efforts should focus primarily on habitat conservation and on
ex-situ conservation through the establishment of an ex-situ population and the maintenance of a seed bank. 相似文献
10.
Flowering phenology and compensation for herbivory in<Emphasis Type="Italic"> Ipomopsis aggregata</Emphasis> 总被引:3,自引:0,他引:3
The mechanisms and circumstances that affect a plant's ability to tolerate herbivory are subjects of ongoing interest and investigation. Phenological differences, and the timing of flowering with respect to pollinators and pre-dispersal seed predators, may provide one mechanism underlying variable responses of plants to herbivore damage. The subalpine wildflower, Ipomopsis aggregata, grows across a wide range of elevations and, because phenology varies with elevation, phenological delays associated with elevation may affect the ability of I. aggregata to compensate for or tolerate browsing. Thus, we examined the response of I. aggregata to herbivory across an elevation gradient and addressed the interactions among phenological delays imposed by damage, elevation, pre-dispersal seed predation and pollination, on I. aggregata's compensatory response. Among high and low elevation populations in areas near the Rocky Mountain Biological Laboratory (RMBL) in Gothic, Colorado, we compared the responses of naturally browsed, artificially browsed (clipped), and unbrowsed (control) plants of I. aggregata. We compared responses in the date of initiation of flowering, timing of peak bloom, floral display, nectar production and sugar concentration, oviposition and fruit destruction by the pre-dispersal seed predator Hylemya sp. (Anthomyiidae), fruit production, and aboveground biomass production. Clipping had the greatest effect on reproductive success and clipped plants at high elevation exhibited the lowest tolerance for herbivory. The effects of browsing appear to be mediated by flowering phenology, and both browsing and elevation delayed flowering phenology. Time needed for regrowth delays flowering, and thus affects the overlap with seed predators and pollinators. As a result of delayed flowering, naturally browsed and clipped plants incurred lower rates of seed predation. In the absence of seed predation, plants would exhibit a lower tolerance to herbivory since naturally and artificially browsed plants had fewer fruits destroyed by Hylemya larvae. We provide additional evidence that, for populations near the RMBL, clipping and natural browsing do not have the same effect on I. aggregata plants. This may be due to the selection of larger plants by herbivores. Although under some conditions plants may tolerate browsing, in areas where the growing season is short a phenological delay imposed by damage is likely to significantly reduce plant fitness. Identifying the mechanisms that allow plants to tolerate herbivore damage will help to develop a general framework for understanding the role of tolerance in plant population and community dynamics, as well as plant-herbivore interactions. 相似文献
11.
Sverre Kobro Linda Søreide Endre Djønne Trond Rafoss Gunnhild Jaastad Peter Witzgall 《Population Ecology》2003,45(1):25-30
Masting of rowan Sorbus aucuparia L. has been studied in 45 sites in southern Norway for 22 years. We present data on the year-to-year variation in fruit setting
of rowan, and show that masting is spatially synchronous in Norway and probably all over Fennoscandia. The apple fruit moth
Argyresthia conjugella Zeller is an important seed predator on rowan. We present data on the abundance of apple fruit moth in rowanberries during
these years and discuss the consequences of masting and intermasting of rowan for apple fruit moth as a pest of apple. We
conclude that growth and climate have little impact on flowering intensity and suggest that masting of rowan is an adaptive
defense against seed predation and a new example of predator satiation: intermast years inhibit predators and prepare the
rowan for the subsequent mast.
Received: September 3, 2001 / Accepted: February 24, 2003 相似文献
12.
Few studies have examined how the number and identity of species in the neighbouring community influences the reproductive
success of particular focal species. Pollen delivery, an important component of fitness of sexual plants, is a function of
not just the floral traits of any particular individual, but of features of the population and community as it depends on
pollinator abundance and preferences. Many pollinators in flowering communities will prefer patches with high floral abundance
or diversity yet may exhibit lower floral constancy when more flowering species are present. Thus, pollination efficiency
could increase or decrease with increased species richness and this will alter the selection pressures placed upon the floral
traits (such as floral colour or reward) of any member of a particular community. Moreover, recent studies have indicated
that plant-pollinator networks are phylogenetically structured (pollinators visit related plant species more than expected
by chance) and this may be an important factor structuring flowering plant communities. Thus, the sheer number of species
within a patch may be less important than the number of closely-related species. We investigate whether species richness or
phylogenetic proximity of coflowering species influences the amount and proportion of conspecific pollen delivered to nodding
onion, Allium cernuum, in fragment patches of Garry Oak meadows in South Western British Columbia, Canada. We find that pollen delivery depended
upon the presence of close relatives far more than on species richness or population density, indicating a central role of
the community structure on pollination in flowering plant communities. Insofar as pollen delivery relates to the relative
number of seeds produced by members of the community, pollination may in turn determine the community structure of the next
generation. 相似文献
13.
In large parts of Europe horse chestnut trees ( Aesculus hippocastanum) suffer from severe defoliation by an alien invasive species, the specialist leaf mining moth Cameraria ohridella (Lepidoptera; Gracillariidae). Heavily infested trees have a drastically shortened period for photosynthesis. We quantified the effect of moth infestation on reproduction of horse chestnut trees in two different cities in central Europe, Bern and Munich. C. ohridella negatively affected seed and fruit weight of A. hippocastanum at both locations. In Munich, seed weight of heavily damaged trees was reduced by almost half. However, the number of seeds per fruit, the number of fruits per inflorescence, and the number of inflorescences per tree did not change due to herbivory. We conclude that C. ohridella mining affects seed quality but not seed quantity. The reduced seed weight may severely impair growth and survival of horse chestnut seedlings and thus may endanger the long-term persistence of A. hippocastanum in its endemic forests in south-east Europe. 相似文献
14.
In plant species, when clonal growth produces a patchy structure and flowering ramets are clustered, the amount of pollen
contributing to reproductive success is often regulated by pollinator efficiency and geitonogamy. The spatial population structure
may influence reproductive success. We examined the clonal structure, the spatial ramet distribution, and their combined effects
on fruit set in a natural population of the insect-pollinated, self-incompatible clonal herb, Convallaria keiskei, in northern Japan. The number of shoots, flowers, and fruits in 1-m2 quadrats were counted at every 5 m grid point in an established 100 × 90-m study plot. From all the quadrats where shoots
existed, leaf samples were collected for allozyme analysis. Using the two spatial parameters of flowering ramet densities
and genotypes, we then constructed individual-based fruit-set models. A total of 236 quadrats contained shoots, and 135 contained
flowering ramets, which indicated expanded distribution of this plant throughout the study plot, while shoots, flowers and
fruits all showed clustering distributions. Allozyme analysis of 282 samples revealed 94 multilocus genotypes. The largest
clone extended to more than 40 m, whereas 56 genotypes were detected in only one sample. Several large clones and many small
clones were distributed close to each other. Fine-scale spatial modelling revealed that the neighbouring flower numbers of
different genotypes, compared with local genet or flower diversity, more influenced fruit set, in which the range of the neighbour
was 14.5 m. These findings indicate that the compatible pollen dispersed by insect pollinators has a significant effect on
sexual reproduction, in this C. keiskei population. Consequently, the spatial structure, which includes both genet distribution and clonal expansion by ramets, had
a significant effect on pollination success. 相似文献
15.
16.
James H. Cane 《Arthropod-Plant Interactions》2018,12(5):657-662
Among associations of plants and their pollinating bees, mutually specialized pairings are rare. Typically, either pollen specialist (oligolectic) bees are joined by polylectic bees in a flowering species’ pollinator guild, or specialized flowers are pollinated by one or more polylectic bees. The bee Andrena astragali is a narrow oligolege, collecting pollen solely from two nearly identical species of death camas (Toxicoscordion, formerly Zigadenus). Neurotoxic alkaloids of these plants are implicated in sheep and honey bee poisoning. In this study, T. paniculatum, T. venenosum and co-flowering forbs were sampled for bees at 15 sites along a 900-km-long east–west transect across the northern Great Basin plus an altitudinal gradient in northern Utah’s Bear River Range. Only A. astragali bees were regularly seen visiting flowering panicles of these Toxicoscordion. In turn, this bee was never among the 170 bee species caught at 17 species of other prevalent co-occurring wildflowers in the same five state region (38,000 plants surveyed). Our field pollination experiments show that T. paniculatum is primarily an outcrosser dependent on pollinator visitation for most capsule and seed set. Thus, both A. astragali and two sister species of Toxicoscordion are narrowly specialized and co-dependent on each other for reproduction, illustrating a rare case of obligate mutual specialization in bee–plant interactions. 相似文献
17.
The pollination of one plant species can be facilitated by the presence of one or more neighboring plant species and evidence
has been found in some rewardless species of orchid that benefit from the presence of rewarding plant species in the neighborhood.
There are two pollination mechanisms by which a non-rewarding orchid attracts pollinators and increases its reproductive success:
(1) A magnetic species effect that occurs even though the flowers do not resemble those of the other species, and (2) floral
mimicry where the mimic’s flower resembles that of the model plant species. Oncidium cosymbephorum is a Mexican rewardless epiphytic orchid whose flowers look like those of the rewarding shrub Malpighia glabra (Malpighiaceae). The resemblance of O. cosymbephorum to the oil-offering flowers of M. glabra attracts the same pollinators, and the fitness of the orchid is higher when M. glabra is present than when it is absent. We evaluated the facilitation by M. glabra of the orchid’s pollination for natural and artificial clumps of O. cosymbephorum close to and far from M. glabra over 4 years. Two experiments were performed at five different study sites to evaluate the effect of the presence and absence
of M. glabra on the reproductive success of O. cosymbephorum. In experiment 1, we recorded fruit set production in natural and artificial monospecific clumps of the orchid, and in natural
and artificial heterospecific clumps of O. cosymbephorum and M. glabra. In experiment 2, we recorded the fruit set of O. cosymbephorum at different sites where individuals grow in monospecific clumps, both before and after cultivated individuals of oil-producing
M. glabra had been planted in their vicinity. Both experiments showed that the reproductive success of O. cosymbephorum was greater in the presence of M. glabra than it was in its absence. This study provides experimental evidence for the magnetic species effect. Floral similarity
between O. cosymbephorum and M. glabra, should be experimentally tested to determine whether it is adaptive. 相似文献
18.
Although aerobiological data are often used in phenological research as an indicator of flowering, airborne pollen concentrations
are influenced by a number of factors that could affect pollen curves. This paper reports on a study of various aspects of
reproductive biology in Q. ilex subsp. ballota, together with environmental factors influencing pollen release and transport, with a view of achieving reliable interpretation
of Quercus pollen curves in Ourense (NW Spain). Aerobiological data were recorded from 2002 to 2004 at two sites in the province of
Ourense. From 1st February to the end of the flowering period, phenological observations were carried out on 19 trees from
the Q. ilex subsp. ballota population found in the Ourense area. Pollen production was calculated for the same trees. The chilling and heating requirements
for triggering development were also calculated. The mean flowering period lasted 11-15 days. Reduced pollen output per catkin
and, especially, a reduced number of catkins per tree in 2003 and 2004, prompted a marked decline in overall pollen production.
Major differences observed in Q. ilex subsp. ballota pollen curves were attributed to the considerable influence both of weather conditions during pollination and pollen production.
In years with high pollen production and weather conditions favouring pollen release, Q. ilex subsp. ballota contributed almost 10% to the total Quercus pollen curve. Around 20% of the pollen trapped was captured before or after flowering periods. 相似文献
19.
Numerous bladderwort (Utricularia) species are distributed worldwide, but their reproductive biology is rarely investigated. Bladderworts are known to depend on tiny organisms to meet a significant proportion of their energy requirement by trapping them in bladders. However, information on the extent of their reliance on insects for pollination success is limited. We examined the reproductive strategy of two Utricularia species viz. Utricularia praeterita and U. babui, endemic to Western Ghats, India. The main aspects of the investigation involved floral biology, breeding system, pollination mechanism, and reproductive success. Flowers of both the species are structured for outbreeding through entomophilous floral suites, herkogamy, protandrous dichogamy and sensitive lobes of the stigma. With nearly 65% natural fruit-set, both the species appeared to be sufficiently open-pollinated. However, pollinators failed to show in plants of U. praeterita while in U. babui there was an apparent mismatch between the extent of fruit-set and pollinator visits. The study demonstrated that in the absence/insufficient visits of pollinators, the two species resort to autonomous selfing. In U. babui, denser patches of plants appeared to be crucial for attracting the pollinators. Both species are self-compatible, and reproductive success is predominantly achieved by delayed autonomous selfing. The sensitive stigma in the species fails to prevent selfing due to diminished herkogamy during the late anthetic stages. It is inferred that in the pollinator-limited environment, delayed selfing contributes to absolute natural fecundity in U. praeterita, while it produces a mixed progeny in U. babui. 相似文献
20.
Disanthus cercidifolius Maxim. var. longipes H.T. Chang usually has two inflorescences growing in opposite directions in the axillae, but occasionally three inflorescences
grow paratactically. The typical flowering process could be divided into 4 periods: “Pre-dehiscence”, “Initial dehiscence”, “Full dehiscence” and “Withering”. Both the natural population and the planted population had a flowering peak of 15–35 days after the first flower bloomed.
There were significant differences between the time courses of flowering of the two populations. Out-crossing is the main
breeding system in this species. And autogamy decreases the risk of reproductive failure of this species. The main insect
pollinators of D. cercidifolius var. longipes are Episyrphus balteatus de Geer, Scaptodrosophila coracina Kikkawa and Peng, Polistes olivaceus de Geer, Apis cerana Fabricius, Nezara viridula L. and Coccinella septempunctata L., and so on. Among the insects, S. coracina and E. balteatus are the most important and efficient pollinators, but others are inefficient pollinators. Though wind pollination is not
efficient, it guarantees reproduction when insect pollinators are not available. “Mass flowering” is an adaptive behavior and reproductive strategy of this species, and “few fruiting” could be caused by the lack of pollinators. 相似文献