Search

The natural environment has been significantly altered by human activity over the past few decades. There is evidence we are now experiencing the sixth mass extinction, as many species of plants and animals are declining in abundance. We focused on the Orchidaceae because this plant family has experienced one of the biggest reductions in distribution. We investigated patterns in species richness and distribution of orchids, the rate and causes of their decrease and extinction, and factors influencing their occurrence in the Czech Republic and Greece. The key findings are: (i) Method of pollination and type of rooting system are associated with their distributions and they are different in the two countries. We assume that these differences might be due to the difference in the orography, distribution of suitable habitats and types of bedrock in these two countries. (ii) The greatest reduction in distribution was recorded for critically endangered taxa of orchids. The number of sites suitable for orchids in the Czech Republic declined by 8-92%. The most threatened orchid species are Spiranthes spiralis, Anacamptis palustris, Epipogium aphyllum and Goodyera repens. The distribution of orchids in the Czech Republic is mainly determined by the distribution of their habitats. (iii) The most important factor affecting the distribution of Czech orchids in South Bohemia is land cover. And the most important types of habitats (types in KVES) are oak and oak-hornbeam forests and agricultural meadows. Based on this information, it should be possible to improve the management that is crucial for maintaining orchid localities. [ABSTRACT FROM AUTHOR]

The optimal acceptance threshold hypothesis provides a general predictive framework for testing behavioural responses to discrimination challenges. Decision-makers should respond to a stimulus when the perceived difference between that stimulus and a comparison template surpasses an acceptance threshold. We tested how individual components of a relevant recognition cue (experimental eggs) contributed to behavioural responses of chalk-browed mockingbirds, Mimus saturninus, a frequent host of the parasitic shiny cowbird, Molothrus bonariensis. To do this, we recorded responses to eggs that varied with respect to two components: colour, ranging from bluer to browner than the hosts' own eggs, and spotting, either spotted like their own or unspotted. Although tests of this hypothesis typically assume that decisions are based on perceived colour dissimilarity between own and foreign eggs, we found that decisions were biased toward rejecting browner eggs. However, as predicted, hosts tolerated spotted eggs more than unspotted eggs, irrespective of colour. These results uncover how a single component of a multicomponent cue can shift a host's discrimination threshold and illustrate how the optimal acceptance threshold hypothesis can be used as a framework to quantify the direction and amount of the shift (in avian perceptual units) of the response curve across relevant phenotypic ranges. [ABSTRACT FROM AUTHOR]

The 'bee avoidance' hypothesis posits that the colour of hummingbird-pollinated flowers will exclude bees, especially in long-tubed flowers, which are more subject to bee nectar robbers. However, many hummingbird-pollinated plants possess bracts, and the role of bract colour in bee avoidance has not previously been tested. We assessed the signal value of bract colours by comparing them with the petals of species with and without bracts. We expected the bracts would contrast and enhance the petal signal more to hummingbirds than to bees, especially in long-tubed flowers. We compared bract signals in the hummingbird and bee visual systems, petal signals between the bract and leaf background, and the relationship between flower length and bract colour. For species with bracts, the bracts contrasted more than petals in the hummingbird visual system, but less in the bee visual system. Petals contrasted more with the bract background than with the leaf background to hummingbirds, but not to bees. Bract colours of long-tubed flowers contrasted less than those of short-tubed flowers to bees. Our results show that bracts are attractive to hummingbirds, and have the potential to exclude antagonists in hummingbird-pollinated plants. These patterns support the bee avoidance hypothesis, especially in long-tubed flowers. [ABSTRACT FROM AUTHOR]

Background and Aims Bird pollination is rare among species in the genus Utricularia, and has evolved independently in two lineages of this genus. In Western Australia, the Western Spinebill, Acanthorhynchus superciliosus, visits flowers of Utricularia menziesii (section Pleiochasia : subgenus Polypompholyx). This study aimed to examine the micromorphology of U. menziesii flowers to assess traits that might be linked to its pollination strategy. Methods Light microscopy, histochemistry and scanning electron microscopy were used. Nectar sugar composition was analysed using high-performance liquid chromatography. Key Results The flowers of U. menziesii fulfil many criteria that characterize bird-pollinated flowers: red colour, a large, tough nectary spur that can withstand contact with a hard beak, lack of visual nectar guides and fragrance. Trichomes at the palate and throat may act as tactile signals. Spur nectary trichomes did not form clearly visible patches, but were more frequently distributed along vascular bundles, and were small and sessile. Each trichome comprised a single basal cell, a unicellular short pedestal cell (barrier cell) and a multicelled head. These trichomes were much smaller than those of the U. vulgaris allies. Hexose-dominated nectar was detected in flower spurs. Fructose and glucose were present in equal quantities (43 ± 3.6 and 42 ± 3.6 g L–1). Sucrose was only detected in one sample, essentially at the limit of detection for the method used. This type of nectar is common in flowers pollinated by passerine perching birds. Conclusions The architecture of nectary trichomes in U. menziesii was similar to that of capitate trichomes of insect-pollinated species in this genus; thus, the most important specializations to bird pollination were flower colour (red), and both spur shape and size modification. Bird pollination is probably a recent innovation in the genus Utricularia, subgenus Polypompholyx, and is likely to have evolved from bee-pollinated ancestors. [ABSTRACT FROM AUTHOR]

Abstract: Plant species that are effective colonisers of transient habitats are expected to have a capacity for uniparental reproduction and show flexibility in pollination systems. Such traits may enable populations to be established from a small number of founding individuals without these populations succumbing to reductions in fecundity arising from pollinator limitation. We tested these predictions for Aloe thraskii (Xanthorrhoeaceae), a succulent treelet that colonises shifting coastal dunes and has both bird and bee pollinators. We performed hand‐pollination experiments, and selectively excluded bird visitors to determine differences in pollinator effectiveness. We measured pollinator visitation rates and fecundity in populations varying in their size, density and isolation distance. Controlled hand‐pollinations revealed that unlike most other Aloe species, A. thraskii is self‐compatible and thus capable of uniparental reproduction. The species does however depend on pollinators and is visited by various bird species as well as by bees. Fruit and seed set are not affected by selective exclusion of birds, thus indicating that bees are effective pollinators. Bird visitation rates increased with increasing plant height and population size, while bee visitation rates increased with increasing population size and density. We found that seed set per flower was lower in large populations than in small populations. These results suggest that establishment of populations of A. thraskii from a small number of individuals is unlikely to be limited by the fecundity of individual plants. [ABSTRACT FROM AUTHOR]

Abstract: Long‐billed hummingbirds are assumed to be better adapted than short‐billed ones for the pollination of long tubular flowers. However, the majority of the empirical evidence is derived from surveys of pollinator feeding performance, which tend to ignore the implications for plant fitness. Here, we tested the long‐billed performance hypothesis from the perspective of the pollinated plant. We conducted a comparative survey to evaluate fecundity in relation to the length of the beak of the pollinating hummingbirds visiting the long and tubular flowers of Costus spiralis (Costaceae), in the Brazilian Atlantic forest. The flowers of C. spiralis were pollinated by three hummingbird species and their nectar was thieved by the bee Eulaema sp. There was no significant difference in the frequency of floral visits nor in the production of seeds among the three hummingbirds in fruits formed from flowers exposed to a single visit by each pollinator. Unexpectedly, our results indicate that the floral morphology of C. spiralis is equally compatible with long‐ and short‐billed pollinators, and is apparently incompatible with pollination by large insects. These findings emphasize the need to test the performance of each floral visitor with the simultaneous estimation of the intensity of the interactions, to increase the accuracy of the measurement of the pollinator's relative importance in studies of plant–pollinator interactions in ornithophilous systems. [ABSTRACT FROM AUTHOR]

Background This study establishes an altiudinal gradient, spanning from the highland Andes (2400 m) to lowland Amazon, as a productive region for the study of bird pollination in Southeastern Peru. The 'Manú Gradient' has a rich history of ornithological research, the published data and resources from which lay the groundwork for analyses of plant-bird interactions. In this preliminary expedition we documented 44 plants exhibting aspects of the bird pollination syndrome, and made field observations of hummingbird visits at three sites spanning the Manú Gradient: 2800 m (Wayqecha), 1400 m (San Pedro), and 400 m (Pantiacolla). Some of the documented plant taxa are underrepresented in the bird pollination literature and could be promising avenues for future analyses of their pollination biology. The Manú Gradient is currently the focus of a concerted, international effort to describe and study the birds in the region; we propose that this region of Southeastern Peru is a productive and perhaps underestimated system to gain insight into the ecology and evolution of bird pollination. [ABSTRACT FROM AUTHOR]

Flowers visited by a broad assemblage of animals may nevertheless be considered to have a specialized pollination system if pollen deposition is effected mainly by a subset of these visitors. The importance of a particular animal group for pollination derives mainly from the relative rate of floral visitation and per-visit effectiveness for pollen deposition. We assessed the relative importance of birds and insects for pollination of the African shrub Syncolostemon densiflorus (Lamiaceae). Flower visitors were observed to evaluate their visitation rates. Virgin flowers were exposed to single visits by nine animal visitor groups to evaluate their effectiveness at depositing pollen on stigmas. We selectively excluded birds and larger insects from flowers to assess the contribution of smaller visitors to pollen deposition and seed set. Sunbirds and insects visited flowers at a similar frequency, but on a per-visit basis, sunbirds deposited more pollen on stigmas than did any of the insect groups, including honeybees, long-proboscid flies, butterflies and day-flying hawkmoths. Selective exclusion of birds and larger insects resulted in a large decline in pollen deposition on stigmas and seed production. These results show that S. densiflorus is pollinated mainly by sunbirds, despite its attraction of a broad assemblage of insect flower visitors. These findings highlight the importance of per-visit pollination effectiveness and selective exclusion for understanding the ecological importance of different flower visitors. [ABSTRACT FROM AUTHOR]

Red flowers are a defining character of the bird-pollination syndrome. Birds do not, however, innately prefer red, suggesting that rather than attracting birds, red flowers may serve to exclude other visitors (e.g., bumblebees). Bees are sometimes considered 'blind' to red, but studies have in fact documented both blue and red preferences in various bee species. These mixed results may be an effect of overly simplistic lab settings. We hypothesized that bees might readily locate red flowers in a simple laboratory environment, but struggle to find the same flowers in a complex, foliated setting. We tested the effects of environmental complexity on visitation to red and blue artificial flowers and on the foraging rate of captive worker bumblebees ( Bombus impatiens). Bees made significantly fewer visits to red flowers when foraging in a complex environment with artificial green foliage, suggesting that red becomes harder to locate in this context than in a simple, leafless environment. Bees also foraged more slowly, on average, in the complex environment, although the difference was apparent only among experienced bees. Our findings provide a possible explanation for previous laboratory tests finding no colour preference in bumblebees. This 'contextual colour-blindness' of bees supports the hypothesis that red evolved as a mechanism for plants to avoid visitation by bees, favouring bird pollination instead. [ABSTRACT FROM AUTHOR]

The genus Ruellia (Acanthaceae) consists of some ca. 350 species that are concentrated in tropical and subtropical regions of the world. Old World Ruellia have never been the focus of explicit phylogenetic study, yet comprise the earliest diverging lineages in the genus and contain upwards of 100 species. We sampled 52 accessions representing 29 OW species of Ruellia for phylogenetic analysis. Results yielded five clades that were strongly supported and marked by morphological synapomorphies. Analyses additionally recovered a newly recognized lineage within the tribe Ruellieae, a small radiation of plants in the deserts of Namibia and Angola, and the name Dinteracanthus is available for reinstatement. Divergence time analysis using a primary fossil calibration revealed relatively young estimates for crown ages of all five clades of OW Ruellia (2.5 Ma - 630,000 ypb) as well as for Dinteracanthus (2.0 Ma). Ancestral state reconstruction of pollination systems among OW Ruellia suggest a minimum of two transitions from short-tongued insect pollination to nocturnal moth pollination, one from short-tongued insect to bird pollination, and one reversal from nocturnal moth pollination back to short-tongued insect pollination. We formally delimit the five clades of OW Ruellia as sections and present a key to aid in their identification: sect. Eusiphon, sect. Dipteracanthus, sect. Madagasikara, sect. Pseudoruellia, and sect. Discifolia. We provisionally treat 77 of 97 species of OW Ruellia among these five sections, with the remaining names considered to be unresolved. [ABSTRACT FROM AUTHOR]

Pitcairnioideae is the second most diverse subfamily of bromeliads (Bromeliaceae), a group exclusive to tropical regions of the New World. Pitcairnioid bromeliads have floral traits assumed to promote outcrossing through biotic pollination systems; however, the reproductive biology of most of the species of this group has not been documented. Pitcairnia heterophylla is an epiphytic (seldom saxicolous) bromeliad occurring from Southern Mexico, into the Northern Andes. We studied the pollination and breeding system of P. heterophylla in an epiphytic population at a mountain forest in Costa Rica from January to April 2013. We performed hand pollination experiments (agamospermy, autonomous self-pollination, hand self-pollination and hand cross-pollination) on 89 flowers from 23 individuals (3-6 flowers per individual) in 2013 flowering season. Nectar production was measured on 18 unvisited flowers of six individuals with a hand-held refractometer. Simultaneously, floral visitors were recorded on eight individuals with trail cameras for a total of 918 hours (115 ± 52 hours per individual, mean ± SE). Under natural conditions, seed set (540.4 ± 55.2) was similar to manually selfed flowers (516.3 ± 41.5) and autonomously selfed flowers (521.1 ± 29.0), but lower to manually outcrossed flowers (670.2 ± 31.3). The flowers of P. heterophylla are self-compatible, capable of autonomous pollination, and non-agamospermous. Intrafloral self-pollination is facilitated by adichogamy and lack of floral herkogamy. The scentless red flowers of P. heterophylla with tubular corollas and nectar production suggested ornithophilic pollination which was confirmed by video recording of 46 hummingbird visits. The most common floral visitor was the short-billed hummingbird Lampornis calolaemus which accounted for 78 % of the visits. However, the visitation rate during the flowering season was low (0.6 visits per day per plant). Selfing in P. heterophylla might be explained as a mechanism of reproductive assurance and to reduce interspecific pollen flow with taxonomically unrelated plants. [ABSTRACT FROM AUTHOR]

In the generally bee-pollinated genus Lotus a group of four species have evolved bird-pollinated flowers. The floral changes in these species include altered petal orientation, shape and texture. In Lotus these characters are associated with dorsiventral petal identity, suggesting that shifts in the expression of dorsal identity genes may be involved in the evolution of bird pollination. Of particular interest is Lotus japonicus CYCLOIDEA 2 ( LjCYC2), known to determine the presence of papillate conical cells on the dorsal petal in L. japonicus. Bird-pollinated species are unusual in not having papillate conical cells on the dorsal petal., Using RT-PCR at various stages of flower development, we determined the timing of expression in all petal types for the three putative petal identity genes ( CYC-like genes) in different species with contrasting floral morphology and pollination syndromes., In bird-pollinated species the dorsal identity gene, LjCYC2, is not expressed at the floral stage when papillate conical cells are normally differentiating in bee-pollinated species. In contrast, in bee-pollinated species, LjCYC2 is expressed during conical cell development., Changes in the timing of expression of the above two genes are associated with modifications in petal growth and lateralisation of the dorsal and ventral petals in the bird-pollinated species. This study indicates that changes in the timing, rather than spatial distribution, of expression likely contribute to the modifications of petal micromorphology and petal size during the transition from bee to bird pollination in Macaronesian Lotus species. [ABSTRACT FROM AUTHOR]

To determine seed removal influence on seed populations, we need to quantify pre- and post-dispersal seed removal. Several studies have quantified seed removal in temperate American deserts, but few studies have been performed in tropical deserts. These studies have only quantified pre- or post-dispersal seed removal, thus underestimating the influence of seed removal. We evaluated pre- and post-dispersal seed removal in the columnar cactus Stenocereus stellatus in a Mexican tropical desert., We performed selective exclosure experiments to estimate percentage of seeds removed by ants, birds and rodents during the pre- and post-dispersal phases. We also conducted field samplings to estimate abundance of the most common seed removers., Birds (10-28%) removed a higher percentage of seeds than ants (2%) and rodents (1-4%) during pre-dispersal seed removal. Melanerpes hypopolius was probably the main bird removing seeds from fruits. Ants (62-64%) removed a higher percentage of seeds than birds (34-38%) and rodents (16-30%) during post-dispersal seed removal. Pogonomyrmex barbatus was probably the main ant removing seeds from soil., Birds and ants are the main pre- and post-dispersal seed removers in S. stellatus, respectively. Further studies in other S. stellatus populations and plants with different life forms and fruit types will contribute to evaluate seed removal in tropical American deserts. [ABSTRACT FROM AUTHOR]

Plant-animal interactions are pivotal for ecosystem functioning, and usually form complex networks involving multiple species of mutualists as well as antagonists. The costs and benefits of these interactions show a strong context-dependency directly related to individual variation in partner identity and differential strength. Yet understanding the context-dependency and functional consequences of mutualistic and antagonistic interactions on individuals remains a lasting challenge. We use a network approach to characterize the individual, plant-based pollination interaction networks of the Canarian Isoplexis canariensis (Plantaginaceae) with a mixed assemblage of vertebrate mutualists (birds and lizards) and invertebrate antagonists (florivores, nectar larcenists, and predispersal seed predators). We identify and quantify interaction typologies based on the sign (mutualistic vs. antagonistic) and strength (weak vs. strong) of animal-mediated pollination and test the relationship with individual female reproductive success ( FRS). In addition, we document pollinator movement patterns among individual plants to infer events of pollen transfer/receipt that define the plant mating networks and test the relationship with FRS. We identify six interaction typologies along a mutualism-antagonism gradient, with two typologies being over-represented involving both mutualists and antagonists and influencing FRS. Plants showing strong mutualistic interactions, but also (weak or strong) interactions with antagonists are relatively better connected in the mating network (i.e., with higher potential to transfer or receive pollen). Thus, mixed flower visitor assemblages with mutualists and antagonists give plants increased their importance in the mating networks, promote outcrossing and increasing both female and male fitness. Our approach helps characterize plant-animal interaction typologies, the context-specificity of diversified mutualisms, and a better forecasting of their functional consequences. [ABSTRACT FROM AUTHOR]

Species of the complex and diverse genera Psychotria and Palicourea are common but little-known elements in many tropical forest ecosystems. DNA-phylogenetic studies and a re-evaluation of morphological characters have recently shown that species of Psychotria subg. Heteropsychotria are nested within Palicourea s.l., which was traditionally separated by exhibiting a bird-pollinated (vs. insect-pollinated) pollination syndrome. In order to render both genera monophyletic groups, species of subg. Heteropsychotria need to be transferred to Palicourea s.l. For Central American species, most of the necessary combinations have already been made. In the course of ongoing research on the phytochemical characterization of species and clades of Costa Rican Palicourea s.l., the nomenclature of Mesoamerican species was revised. As a result, two new combinations and a new name are proposed here: Palicourea horquetensis (Dwyer & Hayden) A. C. Berger & C. M. Taylor is based on Rudgea horquetensis Dwyer & Hayden, Palicourea tonduzii (K. Krause) A. C. Berger is based on Cephaelis tonduzii K. Kraus and Palicourea longiinvolucrata A. C. Berger replaces Psychotria hispidula Standl. In addition, two lectotypes are designated. [ABSTRACT FROM AUTHOR]

Understanding how ecological processes structure species assemblages is a central issue in community ecology. While the influence of plant-pollinator interactions on each other's evolution is well recognized, their role in the assembly of interdependent communities of plants and pollinators is still unclear., Using data from seven communities of hummingbirds and plants that they pollinate from two tropical rain forest types (lowland and montane), we evaluated phylogenetic relationships and signal of functional traits, over space and time, to test predictions on the main processes (environmental filtering, facilitation or competition) that are driving these hummingbird-plant assemblages., Our findings suggest that the main processes driving these assemblages varied between hummingbirds and plants and between habitats, and even among communities at the same habitat. The non-conserved floral trait and the phylogenetic patterns (even or random) give support to the hypothesis of facilitation or competition as processes regulating the composition of plant assemblages. Moreover, the positive relationship between fitness and flowering synchrony suggests facilitation as the most important mechanism for montane plant communities. Distinctively, for lowland plant communities, the combination of non-conserved traits and clustered phylogenetic patterns may be a result of either adaptive radiation or biotic filtering driven by a particular pollinator species that plays a main role as plant community organizer. Lastly, evidence of trait conservatism, together with clustered or even phylogenetic patterns, suggests that facilitation or competition may drive the assembly of montane hummingbird communities, despite the predominance of random phylogenetic patterns., Synthesis. Overall, we present a pathway to identify central ecological processes that may drive the assembly of plant-pollinator communities. We show that different processes related with pollination that vary in space and time may contribute to the assembly of the interdependent tropical communities of plants and pollinators. These findings highlight the importance of considering ecological interactions when evaluating community assembly processes. [ABSTRACT FROM AUTHOR]

Aim All species are imbedded in a network of interactions with other species, which define an important component of their ecological niche. These interactions are dynamic and can change the emergence of vacant niches in the environment. Niche adjustments have been predicted to be particularly common on insular communities as a response to the poor and disharmonic biota of oceanic island - the interaction release hypothesis, however, the phenomena has not yet been reported on continents. Taxonomic groups of specialized nectarivorous birds are present on all continents except in Europe where they became extinct in the Oligocene, likely leaving behind underexplored flower resources. We performed the first community-level assessment of flower visitation by European birds to evaluate if insectivorous and granivorous birds show an interaction release towards consuming flower resources in Europe. Location Larçã - Coimbra, Portugal, Europe. Methods During one year, we collected pollen loads from the forehead of 634 birds. Pollen loads were prepared by acetolysis and all pollen grains were identified under a microscope. All interactions were compiled into a quantitative interaction matrix describing the first pollen-transport network by European birds. Results One-fifth of the bird individuals, corresponding to two thirds of the bird species sampled carried pollen from 45 different types. The vast majority of the plant species found were native but the alien Eucalyptus globulus was by far the species most commonly found in the birds' pollen loads. Overall, the structure of the pollen-transport network from Europe shared many attributes of other networks that include taxonomic groups of specialized nectarivorous birds. Main conclusions We show that the interaction release hypothesis is not exclusive to insular communities but can also be observed in continents, greatly increasing the potential geographical distribution of this phenomenon. However, it seems considerably less pronounced in Europe than in the Galápagos, where it was first described, probably due to the much stronger selective pressures on the simplified ecosystems of oceanic islands. [ABSTRACT FROM AUTHOR]

Optimization of flower phenotypes to ensure pollination by agents differing in their match with fertile flower structures can involve fitness trade-offs if the aspects of the phenotype that enhance the fitness contribution of one pollinator are detrimental for pollination by the other agents. If these trade-offs are substantial, flower optimization for specialized pollination is expected. However, optimization for generalized pollination may also take place in trade-off scenarios, as long as the joint contribution of two or more types of pollinators to global pollination fitness is greater than each individual contribution. We used an observational approach to evaluate the role of pollination fitness trade-offs in flower trait optimization, a matter seldom addressed because of the difficulties in conducting experiments. A pattern-searching tool based on the Pareto front concept, borrowed from the fields of economics and engineering, was used to test for fitness trade-off patterns in the flower shape of four Salvia (Lamiaceae) species. Two are pollinated exclusively either by bees or by hummingbirds; the remaining species have mixed-pollination systems, with varying contributions of bee and hummingbird pollination. The patterning of flower shape in this study suggests a bee-hummingbird pollination trade-off in Salvia, and the optimization of generalized flower shapes. [ABSTRACT FROM AUTHOR]

Animal pollinators and the plants they pollinate depend on networks of mutualistic partnerships and more broadly on the stability of such networks. Based mainly on insect-plant visitation networks, theory predicts that species that are most prone to extinction contribute the most to nestedness, however empirical tests are rare. We used a sunbird-tree visitation network within which were both extinction prone vs non extinction prone sunbird species to test the idea. We predicted that the extinction prone species would contribute the most to nestedness. Using local abundance as a proxy for extinction risk we considered that locally rare sunbird species, by virtue of their small population size and associated demographic stochasticity to be more at risk of extinction than the common species. Our network was not strongly nested and all sunbird species made similar contributions to nestedness, so that in our empirical test, extinction proneness did not predict contribution to nestedness. The consequences of this finding remain unclear. It may be that network theory based on plant-insect mutualisms is not widely applicable and does not work for tree- sunbird mutualistic networks. Alternatively it may be that our network was too small to provide results with any statistical power. Without doubt our study highlights the problems faced when testing network theory in the field; a plethora of ecological considerations can variously impact on results. [ABSTRACT FROM AUTHOR]

Cactus flowers have traditionally been considered to be specialized to certain pollination guilds, but pollination studies reveal that most species are actually generalists. This suggests that floral traits are not always predictive of the animal visitors that pollinate cactus flowers. Here, we studied the pollination of Echinopsis leucantha (Gillies ex Salm-Dyck) Walp., an endemic cactus of Argentina, whose floral traits would suggest that it is pollinated by moths. The floral lifespan and flower availability throughout the reproductive period were evaluated. Field experiments were carried out to study the reproductive system and the identity and effectiveness of floral visitors. Echinopsis leucantha flowers had a nocturnal anthesis time that extended into the following morning. The species was self-incompatible. Floral visitors included moths, bees, and passerine birds. However, diurnal visitors were more effective as pollinators than nocturnal ones. The flowers of E. leucantha were phenotypically specialized (sphingophily); however, the pollination system was functionally and ecologically generalized. The results confirm that generalized pollination systems are widespread among species of the Echinopsis genus with nocturnal flowers, for which diurnal pollinators seem to have a key role in fruit and seed production. Our study constitutes the first record of passerine bird pollination in the Cactaceae for mainland South America. [ABSTRACT FROM AUTHOR]

Pollinator specialisation through exploitation barriers (such as long floral tubes) does not necessarily mean a lack of pollination when the favoured pollinator is rare or absent. Theory predicts that suboptimal visitors will contribute to plant reproduction in the absence of the most effective pollinator. Here I address these questions with Chasmanthe floribunda a long-tubed plant species in the Cape Floristic Region, which is reliant on one species of pollinator, the long-billed Malachite Sunbird. In contrast to short-billed sunbirds, the Malachite Sunbird occurs in lower abundance or is absent in transformed landscapes. Short-billed sunbirds rob and thieve nectar from long-tubed flowers, but their potential contribution towards pollination is unknown., Experiments assessing seed set after single flower visits were performed to determine whether thieving short-billed sunbirds can act as substitute pollinators. To determine whether short-billed sunbirds reduce pollen limitation in transformed areas, pollen supplementation was done by hand and compared to natural fruit set., Short billed sunbirds are unable to act as substitute pollinators, and seed set is significantly lower in the flowers that they visited, compared to flowers visited by long-billed sunbirds. This is substantiated on a landscape scale, where fruit production in Chasmanthe floribunda could artificially be increased by 35% in transformed landscapes, but not so in natural areas., These findings have important consequences for the management and conservation of long-tubed bird-pollinated plant species that exist in recently transformed landscapes. The potential vulnerability of specialised plant species in transformed landscapes is highlighted. [ABSTRACT FROM AUTHOR]

Animal pollinators mediate reproduction of many plant species. Foraging theory suggests that animal pollinators exhibit preferences for common plant species in natural communities (positive frequency-dependent foraging) and temporary single-species specialization (flower constancy) during foraging bouts. Positive frequency dependence may favor common plant species; flower constancy may enhance conspecific pollen transfer particularly in rare plant species. Previous experimental studies suggest that avian pollinators are unlikely to exhibit these behaviors. We studied foraging behavior of Cape Sugarbirds ( Promerops cafer), the main avian pollinator of many Protea species, using focal-plant and focal-bird sampling, assisted by high-resolution maps of the spatiotemporal distribution of Protea individuals and their flowering status. We found that Sugarbird's visitation preference increased with species' relative floral abundance, and that individual Sugarbirds tended to visit single species in sequence. Flower constancy during foraging bouts was significantly higher than expected from random plant-animal encounters at the scale of pollinator movements. Positive frequency dependence may favor the reproduction of abundant plant species while flower constancy may be particularly important for rare plant species. This first simultaneous study of both behaviors in a natural plant-pollinator system shows that bird pollinators exhibit both types of behavior and, in this way, possibly influence plant community structure. [ABSTRACT FROM AUTHOR]

The steep declines over the last quarter century of wild pollinators in the Southwest among native bees, monarch butterflies ( Danaus plexippus L.), hummingbirds, and nectar-feeding bats have come during a time of accelerated climate change, and are likely due to a variety of stresses interacting with climatic shifts. Nevertheless, there is mounting evidence that declining availability and altered timing of floral resources along 'nectar corridors' accessible to pollinators involves climatic shifts as a serious stressor that had been previously underestimated. Longitudinal studies from both urban heat islands and rural habitats in Southwestern North America suggest peak flowering of many wildflowers serving as floral resources for pollinators is occurring three to five weeks earlier in spring than a century ago, leaving 'phenological gaps' in nectar resource availability for certain pollinators. To avoid the threat of what A. Dobson (Professor of Ecology and Evolutionary Biology, Princeton University) and others have termed 'food web collapse,' a range of groups have initiated ecological restoration efforts in semi-arid zones that attempt to (a) assemble more resilient plant-pollinator food chains, and (b) hydrologically restore watercourses to ensure water scarcity will be less likely to disrupt re-assembled food chains in the face of droughts, catastrophic floods, and other correlates of global climate change. We recommend 'bottom-up food chain restoration' strategies for restoring nectar corridors in protected areas on or near geopolitical and land management boundaries in all regions, but particularly in the Southwest or US-Mexico desert border states. We highlight binational and multicultural workshops facilitated to communicate about, and initiate restoration of, mutualistic relationships among plants, pollinators, and people to protected area managers on both sides of the border. [ABSTRACT FROM AUTHOR]

We studied biotically pollinated angiosperms on Macquarie Island, a remote site in the Southern Ocean with a predominately or exclusively dipteran pollinator fauna, in an effort to understand how flower colour affects community assembly. We compared a distinctive group of cream-green Macquarie Island flowers to the flora of likely source pools of immigrants and to a continental flora from a high latitude in the northern hemisphere. We used both dipteran and hymenopteran colour models and phylogenetically informed analyses to explore the chromatic component of community assembly. The species with cream-green flowers are very restricted in colour space models of both fly vision and bee vision and represent a distinct group that plays a very minor role in other communities. It is unlikely that such a community could form through random immigration from continental source pools. Our findings suggest that fly pollination has imposed a strong ecological filter on Macquarie Island, favouring floral colours that are rare in continental floras. This is one of the strongest demonstrations that plant-pollinator interactions play an important role in plant community assembly. Future work exploring colour choices by dipteran flower visitors would be valuable. [ABSTRACT FROM AUTHOR]

Nutrient-impoverished soils with severe summer drought and frequent fire typify many Mediterranean-type regions of the world. Such conditions limit seed production and restrict opportunities for seedling recruitment making protection from granivores paramount. Our focus was on Hakea , a genus of shrubs widespread in southwestern Australia, whose nutritious seeds are targeted by strong-billed cockatoos. We assessed 56 Hakea species for cockatoo damage in 150 populations spread over 900 km in relation to traits expected to deter avian granivory: dense spiny foliage; large, woody fruits; fruit crypsis via leaf mimicry and shielding; low seed stores; and fruit clustering. We tested hypothesises centred on optimal seed defenses in relation to (a) pollination syndrome (bird vs insect), (b) fire regeneration strategy (killed vs resprouting) and (c) on-plant seed storage (transient vs prolonged). Twenty species in 50 populations showed substantial seed loss from cockatoo granivory. No subregional trends in granivore damage or protective traits were detected, though species in drier, hotter areas were spinier. Species lacking spiny foliage around the fruits (usually bird-pollinated) had much larger (4–5 times) fruits than those with spiny leaves and cryptic fruits (insect-pollinated). Species with woody fruits weighing >1 g were rarely attacked, unlike those with spiny foliage and small cryptic fruits. Fire-killed species were just as resistant to granivores as resprouters but with much greater seed stores. Strongly serotinous species with prolonged seed storage were rarely attacked, with an order of magnitude larger fruits but no difference in seed store compared with weakly/non-serotinous species. Overall, the five traits examined could be ranked in success at preventing seed loss from large woody fruits (most effective), fruit clustering, low seed stores, spinescence, to crypsis (least effective). We conclude that the evolution of large woody fruits is contingent on pollinator type (dictates flower/fruit location, thus apparency to granivores), level of serotiny (response to poor soils and fire that requires prolonged seed defense) and presence of a formidable granivore (that promotes strong defense). [ABSTRACT FROM AUTHOR]

Pollination success of animal-pollinated flowers depends on rate of pollinator visits and on pollen deposition per visit, both of which should vary with the pollen and nectar 'neighborhoods' of a plant, i.e., with pollen and nectar availability in nearby plants. One determinant of these neighborhoods is per-flower production of pollen and nectar, which is likely to respond to environmental influences. In this study, we explored environmental effects on pollen and nectar production and on pollination success in order to follow up a surprising result from a previous study: flowers of Ipomopsis aggregata received less pollen in years of high visitation by their hummingbird pollinators. A new analysis of the earlier data indicated that high bird visitation corresponded to drought years. We hypothesized that drought might contribute to the enigmatic prior result if it decreases both nectar and pollen production: in dry years, low nectar availability could cause hummingbirds to visit flowers at a higher rate, and low pollen availability could cause them to deposit less pollen per visit. A greenhouse experiment demonstrated that drought does reduce both pollen and nectar production by I. aggregata flowers. This result was corroborated across 6 yr of variable precipitation and soil moisture in four unmanipulated field populations. In addition, experimental removal of pollen from flowers reduced the pollen received by nearby flowers. We conclude that there is much to learn about how abiotic and biotic environmental drivers jointly affect pollen and nectar production and availability, and how this contributes to pollen and nectar neighborhoods and thus influences pollination success. [ABSTRACT FROM AUTHOR]

Many angiosperm lineages present transitions from bee to hummingbird pollination. The flower design in most of these lineages includes either corolla tubes or nectar spurs, structures that commonly experienced an elongation with the acquisition of hummingbird pollination. It is proposed that this increases the fit between the bird head and flower structures, and isolates or partially blocks bees from the interaction. But can this transition occur if the ancestral flower design lacks tubes or spurs? Here we focus on the transition from bee to hummingbird pollination in the Loasaceae subfamily Loasoideae. Loasoideae flowers have radial corollas with separated petals; therefore, they do not display corolla tubes nor nectar spurs. These flowers also present a whorl of nectar scales and staminodes, unique to the subfamily, which is involved in flower-pollinator fit and in nectar harvesting. To explore flower shape adaptation to hummingbird pollination, we tested for correspondence between pollinators and flower shape in Loasoideae. In order to achieve this, we first compared the evolutionary history of flower phenotype and pollination mode, and then used stochastic character mapping and geometric-morphometric variables in a comparison of alternative evolutionary models. The results of our study suggest that the transition from bee to bird pollination was accompanied by changes in the shape of the staminodial complex, along with the evolution of relatively closed corollas. Moreover, while bird pollination seems to be the end point in the evolution of pollination syndromes in many angiosperm lineages, rodent pollinated flowers probably evolved from ancestral bird pollinated flowers in Loasoideae. Our findings suggest that the evolution of bird pollinated flowers from ancestral bee pollinated flowers does not require the presence of corolla tubes or spurs, and can take place as long as the flower design includes structures participating in flower-pollinator fit. [ABSTRACT FROM AUTHOR]

Providing hummingbirds with artificial feeders containing sugar solution is common practice throughout the Americas. Although feeders can affect hummingbird foraging behavior and abundance, it is poorly understood how far this effect may extend. Moreover, it remains debated whether nectar-feeders have a negative impact on hummingbird-pollinated plants by reducing flower visitation rates and pollen transfer close to the feeders. Here, we investigated the effects of distance to nectar-feeders on a local hummingbird assemblage and the pollination of Psychotria nuda (Rubiaceae), a hummingbird-pollinated plant endemic to the Brazilian Atlantic Rainforest. At increasing distance (0-1000 m) from a feeding-station, where hummingbirds have been fed continuously for the past 13 years, we quantified hummingbird abundance, and rates of flower visitation and pollen deposition on P. nuda. We found that hummingbird abundance was unrelated to distance from the feeders beyond ca. 75 m, but increased steeply closer to the feeders; the only exception was the small hummingbird Phaethornis ruber, which remained absent from the feeders. Plants of P. nuda within ca.125 m from the feeders received increasingly more visits, coinciding with the higher hummingbird abundance, whereas visitation rate beyond 125 m showed no distance-related trend. Despite this, pollen deposition was not associated with distance from the feeders. Our findings illustrate that artificial nectar-feeders may locally increase hummingbird abundance, and possibly affect species composition and pollination redundancy, without necessarily having a disruptive effect on pollination services and plants' reproductive fitness. This may apply not only to hummingbirds, but also to other animal pollinators. [ABSTRACT FROM AUTHOR]

Hummingbirds are the most important group of pollinating birds in the Neotropics and tend to use, concomitantly, more than one plant species as food source. Pollen may be mixed on hummingbirds' body due to the visits to different plant species; therefore, these birds may promote heterospecific pollen deposition (HPD). The hummingbirds potential to promote HPD, the occurrence of HPD and its implications in plant reproduction are scarcely known in the Atlantic Forest. We have studied the transport of pollen by three hummingbird species from the Brazilian Atlantic Forest. We have also checked the actual HPD occurrence under natural conditions in two plant species, namely Canistropsis seidelii and Psychotria nuda. Moreover, we investigated Nidularium innocentii reproductive system evaluating the effect of HPD on its reproduction by simulating a pollen mixture pollination. We found hummingbirds transporting heterospecific pollen mixtures on their bodies, which in turn were deposited onto stigmas of different species. We have also found that mixed pollen deposition had negative effect on the fitness of N. innocentii. We conclude that hummingbirds carry pollen mixtures at the same body parts, leading to potential HPD at the community level. Moreover, hummingbird-plant communities in the Atlantic Rainforest show remarkable similarities in temporal organization and interaction pattern. This suggests that HPD may be a widespread phenomena in these communities. [ABSTRACT FROM AUTHOR]

Many cactus species produce 'bird' flowers; however, the reproductive biology of the majority of these species has not been studied. Here, we report on a study of the pollination of two species from the Cleistocactus genus, cited as an ornithophilous genus, in the context of the different ways in which they are specialised to bird pollination. In addition, we re-evaluate the level of specialisation of previous studies of cacti with bird pollination and evaluate how common phenotypic specialisation to birds is in this family. Both Cleistocactus species exhibited ornithophilous floral traits. Cleistocactus baumannii was pollinated by hummingbirds, whereas Cleistocactus smaragdiflorus was pollinated by hummingbirds and bees. Pollination by birds has been recorded in 27 cactus species, many of which exhibit ornithophilous traits; however, they show generalised pollination systems with bees, bats or moths in addition to birds being their floral visitors. Of all cactus species, 27% have reddish flowers. This trait is associated with diurnal anthesis and a tubular shape. Phenotypic specialisation to bird pollination is recognised in many cactus species; however, it is not predictive of functional and ecological specialisation in this family. [ABSTRACT FROM AUTHOR]

Many mistletoe species produce 'bird'-pollinated flowers; however, the reproductive biology of the majority of these species has not been studied. Psittacanthus auriculatus is a Mexican endemic mistletoe, most common in open, dry mesquite grassland. Knowledge of the reproductive biology of P. auriculatus is essential for understanding species formation and diversification of Psittacanthus mistletoes, but it is currently poorly understood. Thus, we studied floral biology and phenology, nectar production and breeding system and pollination of this species. The hermaphroditic red-pink flowers open from the middle to the tip and petals are curly, but remain partially fused forming a floral tube of ca. 20-mm long. Flowers are partially protandrous, produce large amounts of nectar, last 2 days, and stigma receptivity is highest during the second day. We recorded hummingbirds (Cynanthus latirostris, Hylocharis leucotis, Amazilia beryllina, A. violiceps, Calothorax lucifer, Archilochus colubris) and less commonly butterflies (Agraulis vanillae, Anteos clorinde, Papilio multicaudatus, Phocides urania, Phoebis sennae) as floral visitors. P. auriculatus flowers are self-compatible. However, this mistletoe is an obligate animal-pollinated species, as the sensitive stigma avoids self-pollination. Under natural conditions, reproductive success was higher than in manually selfed or cross-pollinated flowers, likely due to the traplining foraging behaviour of hummingbirds. We suggest that the apparent efficient foraging behaviour of hummingbirds maintains gene flow among P. auriculatus, promoting outcrossing. [ABSTRACT FROM AUTHOR]

Colour is one of the most obvious advertisements of flowers, and occurs in a huge diversity among the angiosperms. Flower colour is responsible for attraction from a distance, whereas contrasting colour patterns within flowers aid orientation of flower visitors after approaching the flowers. Due to the striking differences in colour vision systems and neural processing across animal taxa, flower colours evoke specific behavioural responses by different flower visitors. We tested whether and how yellow flowers differ in their spectral reflectance depending on the main pollinator. We focused on bees and birds and examined whether the presence or absence of the widespread UV reflectance pattern of yellow flowers predicts the main pollinator. Most bee-pollinated flowers displayed a pattern with UV-absorbing centres and UV-reflecting peripheries, whereas the majority of bird-pollinated flowers are entirely UVabsorbing. In choice experiments we found that bees did not show consistent preferences for any colour or pattern types. However, all tested bee species made their first antennal contact preferably at the UV-absorbing area of the artificial flower, irrespective of its spatial position within the flower. The appearance of UV patterns within flowers is the main difference in spectral reflectance between yellow bee- and bird-pollinated flowers, and affects the foraging behaviour of flower visitors. The results support the hypothesis that flower colours and the visual capabilities of their efficient pollinators are adapted to each other. [ABSTRACT FROM AUTHOR]

Relationships among floral biology, floral micromorphology and pollinator behaviour in bird-pollinated orchids are important issues to understand the evolution of the huge flower diversity within Orchidaceae. We aimed to investigate floral mechanisms underlying the interaction with pollinators in two hummingbird-pollinated orchids occurring in the Atlantic forest. We assessed floral biology, nectar traits, nectary and column micromorphologies, breeding systems and pollinators. In both species, nectar is secreted by lip calli through spaces between the medial lamellar surfaces of epidermal cells. Such a form of floral nectar secretion has not been previously described. Both species present functional protandry and are self-compatible yet pollinatordependent. Fruit set in hand-pollination experiments was more than twice that under natural conditions, evidencing pollen limitation. The absence of fruit set in interspecific crosses suggests the existence of post-pollination barriers between these sympatric co-flowering species. In Elleanthus brasiliensis, fruits resulting from cross-pollination and natural conditions were heavier than those resulting from selfpollination, suggesting advantages to cross-pollination. Hummingbirds pollinated both species, which share at least one pollinator species. Species differences in floral morphologies led to distinct pollination mechanisms. In E. brasiliensis, attachment of pollinarium to the hummingbird bill occurs through a lever apparatus formed by an appendage in the column, another novelty to our knowledge of orchid pollination. In E. crinipes, pollinarium attachment occurs by simple contact with the bill during insertion into the flower tube, which fits tightly around it. The novelties described here illustrate the overlooked richness in ecology and morphophysiology in Orchidaceae. [ABSTRACT FROM AUTHOR]

Nectar robbing occurs when floral visitors remove floral nectar through floral damage and usually without providing pollination in return. Even though nectar robbing may have negative, neutral or even positive effects on plant fitness, few studies have investigated temporal and spatial variation in robbing rate and their consequences, particularly in the tropics. In this study, robbing levels were estimated during 3 years in four populations of Salvia gesneriflora, a hummingbird-pollinated shrub endemic to central Mexico that is mainly robbed by birds, carpenter bees and bumblebees. The effect of robbing on nectar availability, flower longevity and on visitation rate by floral visitors was also evaluated. Our results indicate great variation in robbing levels across years and populations and a positive relationship between robbing level and flower abundance per population. Moreover, our results show that nectar availability is about eight times higher in unrobbed flowers than in robbed flowers, and that nectar robbers prefer younger flowers, although lifespan of robbed and unrobbed flowers did not differ statistically. Primary and secondary nectar robbers showed a higher visitation rate compared to legitimate visitors, and neither legitimate nor illegitimate floral visitors seem to discriminate between robbed and unrobbed flowers. These results suggest that robbers may respond to food availability and that no floral visitors apparently could differentiate between robbed and unrobbed flowers. Finally, results show that nectar robbers prefer the youngest flowers, which suggests that strong competition for access to nectar between pollinators and robbers might occur, mainly at the first stages of the flowers. [ABSTRACT FROM AUTHOR]

Sunbird-pollinated plants display a suite of floral adaptations, for example, red tubular flowers, significant volumes of dilute nectar, or a suitable perch from which to forage flowers. In this study we show that two sunbird species were important for seed-set in low-growing, perchless plants of Hyobanche sanguinea and Lachenalia luteola on Kommetjie Slangkop, southern Cape Peninsula, South Africa. Remote video camera footage and field observations showed that malachite sunbirds ( Nectarinia famosa ) and orange-breasted sunbirds ( Anthobaphes violacea ) perched on the ground while visiting flowers of both plant species. Open inflorescences of both species yielded significantly higher seed-set than excluded inflorescences, which showed zero to near zero seed-set. Inflorescences shown on video to have been visited by sunbirds showed significantly higher seed-set than those for which video footage was not obtained, suggesting sunbirds are effective pollinators. Besides being the first documented pollinator information on these two species, our results expand upon the known traits associated with sunbird-pollination systems and suggest that low-growing sunbird-pollinated plants need not evolve perching structures in order to achieve effective visitation. [ABSTRACT FROM AUTHOR]

The article focuses on the stamens of the plant Heliconia wagnerianaalso known as Heliconiaceae, which were used to study the pollination pattern. Topics discussed include hair-triggered mechanism to shoot their sticky pollinium onto bee pollinators, pollination through bird visitations of humming birds, and jack-in-the-box method of pollen transfer.

Biodiversity is declining, with direct and indirect effects on ecosystem functions and services that are poorly quantified. Here, we develop the first global assessment of trends in pollinators, focusing on pollinating birds and mammals. A Red List Index for these species shows that, overall, pollinating bird and mammal species are deteriorating in status, with more species moving toward extinction than away from it. On average, 2.5 species per year have moved one Red List category toward extinction in recent decades, representing a substantial increase in the extinction risk across this set of species. This may be impacting the delivery of benefits that these species provide to people. We recommend that the index be expanded to include taxonomic groups that contribute more significantly to pollination, such as bees, wasps, and butterflies, thereby giving a more complete picture of the state of pollinating species worldwide. [ABSTRACT FROM AUTHOR]

The balance between mutualistic and antagonistic plant-animal interactions and their spatial variation results in a highly dynamic mosaic of reproductive success within plant populations. Yet, the ecological drivers of this small-scale heterogeneity of interaction patterns and their outcomes remain virtually unexplored. We analyzed spatial structure in the frequency and intensity of interactions that vertebrate pollinators (birds and lizards) and invertebrate antagonists (florivores, nectar larcenists, and seed predators) had when interacting with the insular plant Isoplexis canariensis, and their effect on plant fitness. Spatially autocorrelated variation in plant reproductive success (fruit and viable seed set) emerged from the combined action of mutualists and antagonists, rather than reflecting the spatial pattern of any specific animal group. However, the influence of antagonists on plant fitness was stronger primarily due to the florivores' action on earlier reproductive stages, consuming and damaging floral structures before the arrival of pollinators. Our results indicate that the early action of antagonists creates hotspots of increased plant damage, where the effects of later acting mutualists are not translated into increased reproductive benefits. We foresee the potential for antagonists to shape the intra-population mosaics of plant fitness in situations where antagonists outnumber mutualists, when their interactions occur before those of mutualists, and when mutualists can detect and avoid damaged plants while foraging. Severely damaged plants in antagonistic hotspots might be excluded from the mating network and render a limited production of viable seeds, reducing both the growth rate of the plant population and the effective population size. [ABSTRACT FROM AUTHOR]

Variability in floral volatile emissions can occur temporally through floral development, during diel cycles, as well as spatially within a flower. These spatiotemporal patterns are hypothesized to provide additional information to floral visitors, but they are rarely measured, and their attendant hypotheses are even more rarely tested. In Penstemon digitalis, a plant whose floral scent has been shown to be under strong phenotypic selection for seed fitness, we investigated spatiotemporal variation in floral scent by using dynamic headspace collection, respectively solid-phase microextraction, and analyzed the volatile samples by combined gas chromatography-mass spectrometry. Total volatile emission was greatest during flowering and peak pollinator activity hours, suggesting its importance in mediating ecological interactions. We also detected tissue and reward-specific compounds, consistent with the hypothesis that complexity in floral scent composition reflects several ecological functions. In particular, we found tissue-specific scents for the stigma, stamens, and staminode (a modified sterile stamen common to all Penstemons). Our findings emphasize the dynamic nature of floral scents and highlight a need for greater understanding of ecological and physiological mechanisms driving spatiotemporal patterns in scent production. [ABSTRACT FROM AUTHOR]

Cytinus (Cytinaceae) is an enigmatic lineage of parasitic plants distributed in the Mediterranean, Africa and Madagascar, and exhibits variation in floral traits suggestive of multiple pollinator shifts. The flowers of Cytinus sanguineus , a dioecious South African species, are sturdy, bright scarlet, and scentless - a combination of floral characteristics that suggests pollination by nectarivorous birds. However, the emergence of flowers at soil level underneath host shrubs and the absence of perches are not typical features of plants pollinated by sunbirds, which are generally averse to foraging on the ground. We studied the pollination system of C. sanguineus using camera traps, analysis of floral nectar and scent, and spectrophotometry of floral surfaces. We observed that C. sanguineus is pollinated by sunbirds, which readily forage on the ground and transfer pollen on their beaks while drinking copious, diluted nectar from narrowly tubular floral nectaries. High fruit set regardless of spatial separation of male and female flowers indicates efficient pollination. Rodents and insects rarely visit C. sanguineus flowers, likely due to the absence of attractive floral volatiles, and the inaccessibility of nectar for rodents. The pollination system of C. sanguineus is clearly distinguished from those of the rodent-pollinated Cytinus visseri and the ant-pollinated Cytinus hypocistis , where pollinator attraction is achieved through production of specific floral volatiles. Our documentation of bird pollination in Cytinus contributes to understanding of the diversity of pollination systems in this genus. [ABSTRACT FROM AUTHOR]

Pollination syndromes predict the principal animal pollinators of plant species from floral traits. However, the existence of discrete pollination syndromes and the relevance of these syndromes for the effects of animal pollinators on plant reproduction are controversial and a quantitative, trait-based approach may refine the concept of pollination syndromes. Thus far, however, very few studies have simultaneously analysed the importance of signalling, accessibility and reward traits of flowers for the effects of animal pollinators on plant reproduction of multiple species. The genus Protea is an ideal study system because the members of this genus exhibit remarkable variation in functional traits and Protea species are visited by several guilds of animal pollinators, such as birds and insects. We experimentally investigated seven Protea species from the South African fynbos to assess variability in reproduction (seed set, seed mass, germination) in response to pollinator exclusion (full-exclusion, bird-exclusion) and hand-pollination (self-pollen, cross-pollen). To generalise the findings of the experiment, we conducted a meta-analysis of the effects of bird-exclusion on seed set of 14 Protea species, associating effect sizes of bird-pollination with signalling (inflorescence length and diameter), accessibility (inflorescence and style length) and reward traits (length of pollen presenter, nectar volume and sugar concentration). All Protea species were self-compatible, but only two species were to a small degree capable of autonomous selfing. Protea species varied in their dependence on animal pollinators, including species depending exclusively on birds, insects, or both for seed production. Protea species exhibited continuous variation in the effects of bird-pollinators on reproduction, challenging the accuracy of categorical pollination syndromes for predicting pollinator effects on plant reproduction. The meta-analysis showed that the quality of floral rewards, especially nectar sugar concentration, predicts the dependence of Protea reproduction on bird pollinators, whereas the signalling and accessibility traits tested in this study were not important. Beyond revealing new insights into the pollination biology of Protea species, our findings underscore the usefulness of experimental approaches on multiple plant species to test the effects of pollinator guilds on plant reproduction and contribute to a trait-based understanding of the functional determinants of plant–pollinator interactions. [ABSTRACT FROM AUTHOR]

The bird pollination systems of the New and Old Worlds evolved independently, and differ in many aspects. New World plants are often presented as those adapted to hovering birds while Old World plants to perching birds. Most Neotropical studies also demonstrate that in hummingbird species rich assemblages, only a small number of highly specialized birds exploits the most specialized plants with long corollas. Nevertheless, recent research on bird-plant pollination interactions suggest that sunbird pollination systems in the Old World have converged more with the highly specialized hummingbird pollination systems than previously thought. In this study we focus on the pollination systems of the bird pollination syndrome Impatiens species on Mt. Cameroon, West Africa. We show that despite the high diversity of sunbirds on Mt. Cameroon, only Cyanomitra oritis appear to be important pollinator of all Impatiens species. This asymmetry indicates the absence of pair wise co-evolution and points to a diffuse co-evolutionary process resulting in guilds of highly specialized plants and birds; a situation well known from hummingbirds and specialized plant communities of the New World. Additionally, the herbaceous habits of Impatiens species, the frequent adaptations to pollination by hovering birds, and the habitat preference for understory in tropical forests or epiphytic growth, resemble the highly specialized Neotropical plants. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115, 127-133. [ABSTRACT FROM AUTHOR]

Communication of any sort is complex and communication between plants and animals is particularly so. Plant-pollinator mutualisms are amongst the most celebrated partnerships that have received a great deal of attention for many centuries. At the outset, most pollination studies focused on phenotypic matches and invoked co-evolution to explain plant- pollinator interactions, which gave rise to the concept of pollination syndromes. A few centuries later, there has been a substantial shift in the way we view these mutualistic interactions. In a significant departure from a co-evolutionary framework, numerous studies subsequently showed that there is usually only a loose, non-exclusive matching between flowers and their pollinators. Concurrently, the global prevalence of generalized pollination systems was demonstrated repeatedly. However, our understanding of the evolutionary processes that underlie these mutualisms is still limited. Here, we provide a concise review of the state of our knowledge on the evolution of floral traits and pollinator sensory perception and how these together shape the structure and organization of pollination networks. [ABSTRACT FROM AUTHOR]

Darwin recognized the flower's importance for the study of adaptation and emphasized that the flower's functionality reflects the coordinated action of multiple traits. Here we use a multitrait manipulative approach to quantify the potential role of selection acting on floral trait combinations underlying the divergence and maintenance of three related North American species of Silene (Caryophyllaceae). We artificially generated 48 plant phenotypes corresponding to all combinations of key attractive traits differing among the three Silene species (color, height, inflorescence architecture, flower orientation, and corolla-tube width). We quantified main and interaction effects of trait manipulation on hummingbird visitation preference using experimental arrays. The main effects of floral display height and floral orientation strongly influenced hummingbird visitation, with hummingbirds preferring flowers held high above the ground and vertically to the sky. Hummingbirds also prefer traits in a nonadditive manner as multiple two-way and higher order interaction effects were important predictors of hummingbird visitation. Contemporary trait combinations found in hummingbird pollinated S. virginica are mostly preferred. Our study demonstrates the likelihood of pollination syndromes evolving due to selection on trait combinations and highlights the importance of trait interactions in understanding the evolution of complex adaptations. [ABSTRACT FROM AUTHOR]

Plant species distributed across terrestrial islands can show significant genetic divergence among populations if seed and pollen dispersal are restricted. We assessed the genetic connectivity between populations of Grevillea georgeana, restricted to seven disjunct inselbergs in semi-arid Western Australia. The phylogeographical pattern and population genetics of populations were determined using sequence data from two plastid DNA intergenic spacers and ten nuclear microsatellite loci. The plastid DNA markers indicated high genetic differentiation among the majority of populations. Haplotypes were restricted to individual inselbergs, with the exception of two that were shared among three isolated populations that formed part of an elongated greenstone belt and that may be connected via inaccessible populations of G. georgeana. There was also strong differentiation within some of the populations, suggesting long-term isolation and persistence of G. georgeana on these terrestrial islands. Overall, the genetic patterns suggest limited seed dispersal, with differentiation in the plastid DNA genome being driven by genetic drift. In contrast, pollen movement, although generally restricted, may occur between neighbouring populations, resulting in a pattern of isolation by distance in the nuclear markers. This potential for limited or no seed dispersal, but connectivity via pollen flow, should be considered, given that many of the inselbergs are under consideration for resource development. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178, 155-168. [ABSTRACT FROM AUTHOR]

Secondary compounds in nectar may play a decisive role in determining the spectrum of floral visitors on plants. Flowers of the African coral tree Erythrina caffra are visited mainly by generalist passerine nectarivores, such as weavers and bulbuls. As the nectar of this species tastes very bitter to humans, it was hypothesized that secondary compounds may repel sunbirds and honeybees which are common in the same habitats yet seldom consume the nectar. We conducted choice tests using fresh nectar and both sucrose and hexose (glucose/fructose) solutions of the same concentration as the nectar. White-bellied Sunbirds ( Cinnyris talatala) were repelled by nectar of both E. caffra and a related species Erythrina lysistemon, but Dark-capped Bulbuls ( Pycnonotus tricolor) did not discriminate between the Erythrina nectar and control sugar solution in terms of amounts consumed. Honeybees ( Apis mellifera scutellata) probed exposed droplets of E. caffra nectar and a control sugar solution at the same rate, suggesting that there is no volatile deterrent, but they immediately withdrew their proboscis far more often from the droplets of Erythrina nectar than they did from the sugar solution, suggesting that they find Erythrina nectar distasteful. These results contribute to a growing awareness that non-sugar components of nectar can play important functional roles in plant pollination systems. [ABSTRACT FROM AUTHOR]

Plants might be under selection for both attracting efficient pollinators and deterring wasteful visitors. Particular floral traits can act as exploitation barriers by discouraging the unwelcome visitors. In the genus Penstemon, evolutionary shifts from insect pollination to more efficient hummingbird pollination have occurred repeatedly, resulting in the convergent evolution of floral traits commonly present in hummingbird-pollinated flowers. Two of these traits, a reduced or reflexed lower petal lip and a narrow corolla, were found in a previous flight-cage study to affect floral handling time by bumble bees, therefore potentially acting as 'anti-bee' traits affecting preference. To test whether these traits do reduce bumble bee visitation in natural populations, we manipulated these two traits in flowers of bee-pollinated Penstemon strictus to resemble hummingbird-adapted close relatives and measured the preferences of free-foraging bees. Constricted corollas strongly deterred bee visitation in general, and particularly reduced visits by small bumble bees, resulting in immediate specialization to larger, longer-tongued bumble bees. Bees were also deterred-albeit less strongly-by lipless flowers. However, we found no evidence that lip removal and corolla constriction interact to further affect bee preference. We conclude that narrow corolla tubes and reduced lips in hummingbird-pollinated penstemons function as exploitation barriers that reduce bee access to nectaries or increase handling time. [ABSTRACT FROM AUTHOR]

I studied pollination of the Arizona hedgehog cactus ( Echinocereus arizonicus), an endangered plant species occurring in the Superstition Mountains, Arizona, in order to identify the pollinators of the species, determine whether the species is self-incompatible or pollen-limited, and evaluate whether individuals transplanted to make way for habitat disturbance continue to receive pollination. The flowers of E. arizonicus are large, bright red, and cup-shaped. Important flower visitors included hummingbirds and native halictid bees. Flower visitor guilds were similar between the wild population and the transplanted individuals (located in the Boyce Thompson Arboretum in Pinal County, Arizona), although the Arboretum is located at a low elevation and supports much higher abundances of flowering plants and pollinators than occur in the wild sites. Pollination treatments indicated E. arizonicus is highly self-incompatible but not pollen-limited and hummingbird visitation is relatively more important to seed set than is insect visitation but both contribute to total seed counts. [ABSTRACT FROM AUTHOR]