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1.
Caladenia behrii, a sexually deceptive orchid, is an endangered terrestrial orchid endemic to the Adelaide Hills, South Australia. We examined pollination success among individuals of different colours and heights in three populations of C. behrii in the northern Adelaide region. The labellum of C. behrii varies from cream to deep maroon. Over five years, the pollination success (pollinia deposited on stigma) of four colour groups (maroon, maroon and cream, hatched, and cream) was assessed for a total of 782 flowers. Labellum colour had no effect on the pollination success of individuals, indicating no frequency-dependent selection. It is likely that pollinators use the sexual pheromone mimic produced by the flowers as the main orientation cue. For three years the height of pollinated C. behrii individuals was recorded, along with the height of the nearest non-pollinated neighbour (distance of labellum from the ground, rather than stem length). Although a range of different heights was pollinated at population level, individual flowers that were taller than their closest neighbours were significantly more likely to be pollinated. Flower head height was not correlated with opening date and was greater for orchids growing among grass-tree leaves. Results imply that pollinators are more successful in finding tall flowers than short ones for visual and/or olfactory reasons; however, the effect of height preference is eliminated at population level.  相似文献   

2.
    
蜂媒花很少呈红色,这可能是由于蜂类的眼睛缺少红光受体,因而较难搜寻红色目标。尽管有实验研究过蜂类对红色的反应,但所用目标多为纯红色。而人类感受到的红色中其实包含细微的色调差别,这些差别还甚少受到关注。我们在本研究中检验了如下假说:红花中的紫外反射组分能够增加其彩调反差,因而增强其对蜂类的吸引力。紫草科的密花滇紫草(Onosma confertum)由熊蜂传粉,其花为红色,但紫外反射明显。本研究利用该植物设计了表型操控实验,在野外检验了紫外反射对传粉者访花行为的影响。我们还在受控环境下检验了无经验熊蜂的色彩偏好。利用两个色彩模型评估熊蜂的色彩感受,用彩调反差和明度反差两个参数进行估计。研究发现,自然状态下及无经验的饲养熊蜂均偏好访问具有紫外反射的红色目标。色彩模型分析表明,具紫外反射的红花对蜂而言色彩更纯,且与叶片背景的彩调反差更大;而它们与无紫外反射的红花在明度反差方面(以绿光受体的反差估计)表现相似。这些结果表明,密花滇紫草红色花朵中的紫外反射组分增加了其彩调反差,增强了其对熊蜂的吸引力。我们推测,由于某些传粉者(例如蜂类)无红光受体,对由它们传粉的红色花而言,光谱中的副反射特征(例如紫外反射)可能是其花色中的必要组分。  相似文献   

3.
We tested whether selection by pollinators could explain the parapatric distribution of coastal red- and inland yellow-flowered races of Mimulus aurantiacus (Phrymaceae) by examining visitation to natural and experimental populations. As a first step in evaluating whether indirect selection might explain floral divergence, we also tested for local adaptation in early life stages using a reciprocal transplant experiment. Hummingbirds visited flowers of each race at similar rates in natural populations but showed strong (>95%) preference for red flowers in all habitats in experimental arrays. Hawkmoths demonstrated nearly exclusive (>99% of visits) preference for yellow flowers and only visited in inland regions. Strong preferences for alternative floral forms support a direct role for pollinators in floral divergence. Despite these preferences, measures of plant performance across environments showed that red-flowered plants consistently survived better, grew larger and received more overall pollinator visits than yellow-flowered plants. Unmeasured components of fitness may favour the yellow race in inland habitats. Alternatively, we document a marked recent increase in inland hummingbird density that may have caused a change in the selective environment, favouring the eastward advance of red-flowered plants.  相似文献   

4.
外来种入侵的生物学与生态学基础的若干问题   总被引:62,自引:0,他引:62  
外来物种的入侵及其所造成的危害已越来越为人们所认识。一个外来物种入侵一个新的生境无疑要具备一定的条件 ,尽管目前对这种条件的研究还只是初步的。首先从其自身来说 ,需要有足够的入侵性 ,这可以认为是入侵种的生物学基础 ,可能表现为具有多倍性、一定的遗传变异、杂合性或表型可塑性 ,以及不同的交配系统等 ;其次一个物种的入侵成功还取决于入侵生境的可入侵性 ,这可以认为是入侵种的生态学基础 ,而新的种间关系的形成 ,尤其是入侵种与其他种类的互惠共生关系的建成是关键。本文主要介绍了有关入侵种的生物学和生态学基础中的一些最新进展 ,希望有助于我国学者对相关研究内容的开展以及对有害外来种入侵的防治  相似文献   

5.
Many angiosperms have arranged their flowers in inflorescences forming a distinct signalling unit to flower visitors. In some species, the flowers of inflorescences undergo a temporal colour change corresponding exactly to a change in the reward status. Based on information obtained from the spectral reflection curves of pre-change and postchage colours of flower corollas and/or floral guides, it was possible to demonstrate that the colour phase associated with reward closely corresponds to the visual stimuli which trigger behavioural responses of inexperienced flower visitors, and that the colour phase associated with less reward corresponds to visual stimuli less attractive to naïve flower visitors. Reciprocal colour changes were not observed. It is to be assumed that the unidirectionality of floral colour changes is an adaptation of angiosperms aimed at the guidance of first-time flower visitors. Signalling reward to inexperienced flower visitors is an additional function of floral colour changes. The main function of floral colour changes, however, is to provide cues with which the flower visitors can learn to associate one colour phase with reward.  相似文献   

6.
    
1. Variation in spring phenology – like tree budburst – affects the structure of insect communities, but impacts of autumn phenology have been neglected. Many plant species have recently delayed their autumn phenology, and the timing of leaf senescence may be important for herbivorous insects. 2. This study explored how an insect herbivore community associated with Quercus robur is influenced by variation in autumn phenology. For this, schools were asked to record, across the range of oak in Sweden, the autumn phenology of oaks and to conduct a survey of the insect community. 3. To tease apart the relative impacts of climate from that of tree phenology, regional tree phenology was first modelled as a function of regional climate, and the tree‐specific deviation from this relationship was then used as the metric of relative tree‐specific phenology. 4. At the regional scale, a warmer climate postponed oak leaf senescence. This was also reflected in the insect herbivore community: six out of 15 taxa occurred at a higher incidence and five out of 18 taxa were more abundant, in locations with a warmer climate. Similarly, taxonomic richness and herbivory were higher in warmer locations. 5. Trees with a relatively late autumn phenology had higher abundances of leaf miners (Phyllonorycter spp.). This caused lower community diversity and evenness on trees with later autumn phenology. 6. The findings of the present study illustrate that both regional climate‐driven patterns and local variation in oak autumn phenology contribute to shaping the insect herbivore community. Community patterns may thus shift with a changing climate.  相似文献   

7.
    
Flower change in Oenothera drummondii Hooker as a response to pollinators' visits. The colour and shape of flowers of Oenothera drummondii change owing to senescence, pollination and/or nectar withdrawal. This phenomenon is interpreted as a signal emitted by the plant to 'inform' the potential pollinator of its new status as a rewardless flower. This method of signalling might be important for the pollinators in order to save energy in seeking the correct flowers and for the plant to ensure visits to those flowers that have not yet been visited.  相似文献   

8.
  总被引:1,自引:0,他引:1  
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9.
    
  1. The invasive yellow‐legged hornet (Vespa velutina) was first detected in mainland Portugal in September 2011. The lack of information regarding the processes of species spread has hampered the development of adequate measures to mitigate the potential impact of this invasive predator.
  2. Crowdsourced data, i.e., information opportunistically reported by citizens, can facilitate the collection of numerous species occurrence records over large spatial scales, which can be valuable to understand the expansion of invasive species. Here, using validated crowdsourced data on the precise location of 49 013 nests, we: (i) update information regarding V. velutina distribution in Portugal; (ii) estimate the species expansion rate; and (iii) analyse the patterns of nests distribution at national and local scales.
  3. The species is currently distributed over an area of approximately 57 000 km2, which corresponds to 62% of mainland Portugal. We estimated an average rate of 37.4 ± 13.2 km/year for V. velutina expansion. Vespa velutina nests presented an aggregated distribution and nest density at the urban local‐scale was estimated in 5.4 ± 3.3 nests/km2. The observed decrease in the nearest‐neighbour nest distance over the years suggests that the density of nests has not reached its limit.
  4. We advocate that the development of a cheap and rapid method for nest detection and the study of fine‐scale mechanisms leading to V. velutina dispersal are important steps to identify colonisation pathways and plan management approaches aiming to halt species spread and impact in apiaries.
  相似文献   

10.
Pollen-Foraging Dynamics of Subalpine Bumblebees (Bombus Latr.)   总被引:1,自引:0,他引:1  
Abstract A 23-year study on Mount Rainier of nectar-foraging hummingbirds and pollen-foraging bumblebees (Bom-bus Latr.) indicated a constant relative frequency of Bombus species in the area and a wide occurrence of insect species on flowers plus a wide range of flower species pollinated by a single insect. Early-blooming plants had a high queen/worker pollinator ratio, while workers predominated on later-blooming plants. No altitudinal difference in distribution of Bombus species occurred. Analysis of 955 corbicular pollen loads from 1158 bumblebees collected yielded 49.5% monolecty for queens and 34.5% for workers with a wider range for queens than for workers. Colors of corollas photographed in visible and ultraviolet light corresponded to the visual spectra of animal pollinators. In the stable plant-pollinator community investigated, pollinating insect activity appears phenologically controlled by floral anthesis and behaviorally related to floral form and function. Bumblebee tongue length, however. Is not a valid determinant for foraging niche separation except in Castilleja with a deep corolla tube accommodating long tongues of hummingbirds and bumblebees. It is concluded that in a biotic community well-coordinated with the physical environment, limited flower constancy of pollen-foraging pollinators appears to contribute a necessary degree of adaptive versatility through sharing of insect and floral resources. Flower constancy is primarily a function of the circumstance in which a pollinator operates and not simply a characteristic of the pollinator itself.  相似文献   

11.
    
The deceptive Iris lutescens (Iridaceae) shows a heritable and striking flower colour polymorphism, with both yellow‐ and purple‐flowered individuals growing sympatrically. Deceptive species with flower colour polymorphism are mainly described in the family Orchidaceae and rarely found in other families. To explain the maintenance of flower colour polymorphism in I. lutescens, we investigated female reproductive success in natural populations of southern France, at both population and local scales (within populations). Female reproductive success was positively correlated with yellow morph frequency, at both the population scale and the local scale. Therefore, we failed to observe negative frequency‐dependent selection (NFDS), a mechanism commonly invoked to explain flower colour polymorphism in deceptive plant species. Flower size and local flower density could also affect female reproductive success in natural populations. Pollinator behaviour could explain the positive effect of the yellow morph, and our results suggest that flower colour polymorphism might not persist in I. lutescens, but alternative explanations not linked to pollinator behaviour are discussed. In particular, NFDS, although an appealingly simple explanation previously demonstrated in orchids, may not always contribute to maintaining flower colour polymorphism, even in deceptive species.  相似文献   

12.
13.
  总被引:2,自引:0,他引:2  
There is growing appreciation that the ecological factors which impact on rates of pollen transfer can contribute significantly to reproductive trait evolution in plants. In heterostylous species, several studies support Darwin's claim that the reciprocal positions of stigmas and anthers enhance inter‐morph mating in comparison to intra‐morph mating and thus the maintenance of the polymorphism. In this study, we evaluate the relative importance of intra‐morph and inter‐morph pollen transfers in Narcissus assoanus, a species with dimorphic variation in style length but non‐reciprocity of anther positions. This stigma‐height dimorphism represents a transitional stage in theoretical models of the evolution of distyly. Seed set variation on recipient plants with donor plants of a single morph in experimental arrays in a natural population illustrate that inter‐morph cross‐pollination is more efficient that intra‐morph cross‐pollination as a result of high rates of pollen transfer from long‐styled to short‐styled plants. The observed rates of pollen transfer satisfy the theoretical conditions for the establishment of a stigma‐height dimorphism in an ancestral monomorphic long‐styled population in pollen‐limited situations. These results provide experimental evidence for the Darwinian hypothesis that enhanced inter‐morph cross‐pollination facilitates not only the maintenance of heterostyly but also the establishment of transitional forms implicated in the evolution of this polymorphism.  相似文献   

14.
    
Conspicuous body colouration in sedentary predators such as orb web spiders seems paradoxical as potential prey can see and avoid the webs. Several studies have demonstrated that rather than deterring prey, the colours act as sensory traps for flower‐seeking insects. In chromatically polymorphic species, the existence of more than one colour morph may lead to differing levels of prey attraction. To explore these issues, we studied a neotropical orb web spider, Verrucosa arenata, which shows colour polymorphism with predominantly white or yellow abdomen colours. We asked whether a particular morph is dominant in the population, and whether a particular morph is associated with enhanced foraging success and body condition. Here we showed that although yellow morphs attracted more prey, white morphs were in better body condition. We showed that model prey such as honeybees are able to discriminate between the morphs. We discuss these findings in relation to the functional significance of bright body colouration and colour polymorphism in spiders.  相似文献   

15.
16.
    
  1. Red Lists assess the extinction risk of species and are an important tool to prioritise species conservation and management measures. Worldwide, quantitative IUCN criteria are used to estimate the threat status of species at the regional level.
  2. In Flanders (north Belgium), about 70 000 distribution records of ladybirds were collected in 36% of all the grid cells (1 × 1 km2) since 1990 during a large‐scale citizen‐science project.
  3. Applying the IUCN criteria to the 36 resident ‘conspicuous’ ladybirds in Flanders resulted in two Regionally Extinct species, three Endangered species and six Vulnerable species. A further seven species were considered Near Threatened and the remaining 15 species (39%) were assessed as Least Concern. Three species were classified as Data deficient. Using the Red List status, we delineated ladybird hotspots that were mainly located in grid cells with large areas of Natura2000 sites.
  4. For calculating a distribution trend, we advocate the use of a high grid cell resolution (e.g. 1 × 1 km2 or 5 × 5 km2).
  5. The ladybird data set from Flanders provides evidence that IUCN Red List criteria can be applied to this charismatic, but relatively under‐surveyed insect group. For estimating the geographic range, the use of extent of occurrence instead of area of occupancy is advisable when the survey coverage is relatively low. We discuss the opportunities of the availability of a ladybird Red List for regional conservation measures.
  相似文献   

17.
What rules determine whether bumble bees continue exploitingplants of the species just visited or switch to another species?To tackle this question, we recorded handling times and flighttimes from bees foraging in a natural meadow containing fiveplant species. Inter- and intra-specific plant distances werequantified. The bee-subjective colors of the five species weredetermined; two of these species had similar colors and structures,while three species were distinct from all others. The followingrules were identified: (1) The decision to switch species wascorrelated with previous flower handling time, which we assumeis a function of the reward amount received at the flower. Aftershort handling times, the probability of switching to anotherspecies increased, whereas it decreased after long handlingtimes. This difference became even greater if the bee had hada run of several short or several long handling times. (2) Constantflights (those between flowers of the same species) and transitionflights (those between flowers of different species) followedstereotyped temporal patterns independent of the distances betweenflowers. Constant flights within five plant species consistentlyhad median durations of about 2 seconds, whereas median transitiontimes between species took 3–6 seconds. (3) This temporalrule broke down, however, if the flowers of two species hadsimilar colors, in which case transition flights had equal dynamicsas constant flights. (4) Bees switched more frequently fromrare than from common species but even more frequently betweensimilar species. We conclude that the bees' choices were determinedby a set of rules that guided them to stay with the currentplant species as long as flowers were rewarding and availablewithin close distance but to switch to another species if flowersoffered low rewards or were not encountered at close range  相似文献   

18.
    
Citizens’ observations of wildlife offer a wealth of information. Such data, however, may be prone to biases or inaccuracies — in particular, the over-reporting of novel species and under-reporting of common or mundane species. Few studies have assessed the relationship between unstructured and structured observations using long-term data. We compared 69 years of voluntary bird sightings, recorded in the regular publication of Peterborough Field Naturalists (PFN), 1948–2016, to systematic Christmas Bird Counts (CBC; during winter) and Breeding Bird Surveys (BBS; during spring) in central Ontario, Canada. We focused on seven species that had expanded their ranges into the area: Northern Cardinal (Cardinalis cardinalis), House Finch (Haemorhous mexicanus), Purple Finch (Haemorhous purpureus), Red-bellied Woodpecker (Melanerpes carolinus), Wild Turkey (Meleagris gallopavo), Canada Goose (Branta canadensis), and American Robin (Turdus migratorius). For each species, we compared the first record, the annual number of sightings, and the annual relative abundance from the PFN to the first record and annual relative abundance in the CBC and BBS. We anticipated that naturalists’ accounts would be more sensitive to the arrival of novel species but would underestimate abundance as the species became common.In general, our results agreed with these predictions. In 11 of 12 cases, the naturalists detected a species well in advance of the CBC and BBS — on average by 1½ decades (range: 5–33 years). The correlations in bird abundance between unstructured (PFN) and structured (CBC and BBS) data were variable; most were weak and negative. We found significant negative correlations for the two most common species, Northern Cardinal (winter) and House Finch (spring), as well as for Wild Turkey (winter), and a positive correlation for the rarest species, the Red-bellied Woodpecker (spring). We surmise that novelty underlies these results — that rarity increases the likelihood of reporting by non-professionals. We conclude that unstructured observations are valuable in detecting novel species, but they may be inconsistent, even inverse, indicators of the abundance of expanding species, once established.  相似文献   

19.
A single adult Coccinella novemnotata (the nine-spotted lady beetle) was recently discovered by a Cornell University student amongst a series of specimens collected in early October 2006 in Arlington, Virginia. The specimen is the first individual collected in eastern North America in over fourteen years and is only the sixth of its species known to be collected anywhere in North America in the last ten years. This discovery reopens questions regarding the current status of this once common species. Interactions with exotic species, global climate change, and shifting land use patterns have all been postulated as possible factors in this species decline. This discovery is the first in a new program in the USA designed to educate the public regarding biodiversity and conservation and to engage them in a survey of native and exotic lady beetle species.  相似文献   

20.
    
Non‐rewarding orchids rely on various ruses to attract their pollinators. One of the most common is for them to resemble flowers sought by insects as food sources. This can range from generalized food deception to the mimicry of specific sympatric food plants. We investigated the basis of pollinator deception in the European food‐deceptive orchid Traunsteinera globosa, which has unusually compact flowerheads resembling those of sympatric rewarding species of Knautia and Scabiosa (Dipsacaceae), and Valeriana (Caprifoliaceae). Visual signals of T. globosa are similar in both fly and bee vision models to those of the sympatric food plants used in the choice experiments, but scent signals are divergent. Field experiments conducted in Austria and the Czech Republic showed that both naive and experienced (with respect to visitation of T. globosa) insect species approached the orchids at the same rate as food plants, but direct contact with orchid flowers was taxon specific. Flies were most easily duped into probing the orchid, and, in doing so, frequently received and deposited pollinaria, whereas most bees and butterflies avoided landing on orchid flowers. We conclude that T. globosa is a mimic of a guild of fly‐pollinated plants, but the ecological dependence of the orchid on its models remains to be fully tested. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180 , 269–294.  相似文献   

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