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Combined studies of the communities and interaction networks of bird and insect pollinators are rare, especially along environmental gradients. Here, we determined how disturbance by fire and variation in sugar resources shape pollinator communities and interactions between plants and their pollinating insects and birds. We recorded insect and bird visits to 21 Protea species across 21 study sites and for 2 years in Fynbos ecosystems in the Western Cape, South Africa. We recorded morphological traits of all pollinator species (41 insect and nine bird species). For each site, we obtained estimates of the time since the last fire (range: 2–25 calendar years) and the Protea nectar sugar amount per hectare (range: 74–62 000 g/ha). We tested how post‐fire age and sugar amount influence the total interaction frequency, species richness and functional diversity of pollinator communities, as well as pollinator specialization (the effective number of plant partners) and potential pollination services (pollination service index) of insects and birds. We found little variation in the total interaction frequency, species richness and functional diversity of insect and bird pollinator communities, but insect species richness increased with post‐fire age. Pollinator specialization and potential pollination services of insects and birds varied differently along the environmental gradients. Bird pollinators visited fewer Protea species at sites with high sugar amount, while there was no such trend for insects. Potential pollination services of insect pollinators to Protea species decreased with increasing post‐fire age and resource amounts, whereas potential pollination services of birds remained constant along the environmental gradients. Despite little changes in pollinator communities, our analyses reveal that insect and bird pollinators differ in their specialization on Protea species and show distinct responses to disturbance and resource gradients. Our comparative study of bird and insect pollinators demonstrates that birds may be able to provide more stable pollination services than insects. [ABSTRACT FROM AUTHOR]

Traits mediate mutualistic and antagonistic interactions between plants and animals, and should thus be useful for predicting trophic species interactions. Studies to date have examined the importance of morphological trait matching for plant–animal interactions, but have rarely explored the extent to which these interactions are shaped by matching between energetic provisions of plants and energetic demands of animals.We tested whether energetic and/or morphological trait matching shapes interactions between Protea plant species and their interacting animal mutualists and antagonists in the Cape Floristic Region, South Africa.We recorded interactions between 22 Protea species, pollinating insects and vertebrates as well as seed predators (endophagous insect larvae in protea cones) at 21 study sites. To relate species interactions to matching trait pairs, we measured key morphological traits (shape and size of flower heads and seed cones, and mouth part length as well as body length) and quantified the animals' energetic demands (metabolic rate) together with the plants' energetic provisions (nectar sugar amount, seed‐to‐cone mass ratio). We calculated log ratios of both energetic and morphological traits between animals and plants as predictor variables for the number of observed interactions between Protea species and their animal interaction partners.For both mutualistic and antagonistic interactions, we found significant effects of morphological and energetic trait ratios on the interactions between plants and animals. Trait ratios accounted for 11% to 22% of variation in species interactions. Consistent with energetic trait matching, we found a hump‐shaped relationship between interaction frequency and log ratios of energetic traits of animals and plants, indicating that interactions were most frequent at intermediate log ratios between energetic demand and provision. Effects of morphological trait ratios on interactions were statistically supported in most cases, but were variable in the magnitude and shape of the predicted relationships.Across animal taxa and interaction types, energetic traits had more consistent effects on interactions between plants and animals than morphological traits. This suggests that energy can function as an important interaction currency and facilitate the understanding and prediction of trophic species interactions. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

With the current global concerns about pollinators, relationships between species interactions and diversity are pivotal. If pollinator communities depend strongly on the diversity of flowering plants and vice versa, anthropogenic influences—whether positive or negative—on one partner will cause changes in the other. Here we ask whether nectarivorous bird communities are structured by resource abundance (Proteaceae nectar) or Proteaceae diversity at different spatial scales in the Cape fynbos of South Africa. On a small spatial scale, we sampled 34 one‐hectare plots across the Cape Floristic Region (CFR) for flowering Proteaceae species, number of inflorescences, nectar volume, vegetation age, nectar‐feeding bird abundance and species richness. At small scale, nectar—rather than vegetation structure or plant community composition—was the most strongly correlated to nectar‐feeding bird diversity and abundance. On a landscape scale we investigated the spatio‐temporal flowering patterns of ornithophilous Proteaceae throughout the CFR. Similar flowering patterns—with a winter floral abundance peak—were found throughout the region, but Protea, Leucospermum and Mimetes showed complementary flowering periods. At large spatial scales ornithophilous Proteaceae species richness is strongly correlated—more so than plant or floral abundance—to the nectar‐feeding bird community. At large spatial scales resource diversity—and at a smaller scale resource abundance, shapes nectar‐feeding bird communities. Providing high volumes of nectar sugar throughout the year is key to restore the nectar‐feeding bird communities in small conservation areas. [ABSTRACT FROM AUTHOR]

Communities are mostly composed of rare species; yet, the factors that determine their patterns of occurrence remain obscure. Theory predicts that, in contrast with common species, the occurrence of rare species will be poorly correlated with environmental variables (niches) and more affected by stochasticity (ecological drift), but how this pattern varies across different trophic groups is still poorly understood. Here, we compared the ability of environmental variables (bottom–up biotic niches) to predict the occurrence of plant‐dwelling arthropods across different abundance classes in the Cape Floristic Region of South Africa. We compared three trophic groups, including 104 herbivorous hemipteran, 171 parasitoid wasp and 84 spider species, totalling 4511 individuals in 48 quadrats. To quantify bottom–up biotic niches, we studied the influences of species composition of plants on hemipterans, and of plants and hemipterans on spiders and wasps. We compared the observed strength of the correlation between rare species and their niches with expectations that were generated by repeatedly rarefying abundant species. A large proportion of arthropod species were very rare, i.e. with only one or two individuals (49–55%). Although rarefying abundant species greatly decreased the correlation with bottom–up biotic niches, bottom–up biotic niches generally better predicted the occurrence of rarefied abundant species than very rare ones, suggesting a greater influence of drift on very rare arthropods. That is, (very) rare arthropods are distributed more randomly than rarefied abundant species. Nevertheless, trophic groups differed in the details of their response to bottom–up biotic niches. Plant species composition was a better predictor of rarefied abundant than truly rare hemipterans. In contrast, the importance of bottom–up biotic niches among abundance classes varied less visibly in spiders and wasps. Our study thus suggests that the importance of niches in structuring arthropod communities depends on species rarity and trophic group. [ABSTRACT FROM AUTHOR]

The global increase in the proportion of land cultivated with pollinator‐dependent crops implies increased reliance on pollination services. Yet agricultural practices themselves can profoundly affect pollinator supply and pollination. Extensive monocultures are associated with a limited pollinator supply and reduced pollination, whereas agricultural diversification can enhance both. Therefore, areas where agricultural diversity has increased, or at least been maintained, may better sustain high and more stable productivity of pollinator‐dependent crops. Given that >80% of all crops depend, to varying extents, on insect pollination, a global increase in agricultural pollinator dependence over recent decades might have led to a concomitant increase in agricultural diversification. We evaluated whether an increase in the area of pollinator‐dependent crops has indeed been associated with an increase in agricultural diversity, measured here as crop diversity, at the global, regional, and country scales for the period 1961–2016. Globally, results show a relatively weak and decelerating rise in agricultural diversity over time that was largely decoupled from the strong and continually increasing trend in agricultural dependency on pollinators. At regional and country levels, there was no consistent relationship between temporal changes in pollinator dependence and crop diversification. Instead, our results show heterogeneous responses in which increasing pollinator dependence for some countries and regions has been associated with either an increase or a decrease in agricultural diversity. Particularly worrisome is a rapid expansion of pollinator‐dependent oilseed crops in several countries of the Americas and Asia that has resulted in a decrease in agricultural diversity. In these regions, reliance on pollinators is increasing, yet agricultural practices that undermine pollination services are expanding. Our analysis has thereby identified world regions of particular concern where environmentally damaging practices associated with large‐scale, industrial agriculture threaten key ecosystem services that underlie productivity, in addition to other benefits provided by biodiversity. [ABSTRACT FROM AUTHOR]

Summary: Volatile emissions may play a key role in structuring pollination systems of plants with morphologically unspecialised flowers. Here we test for pollination by small mammals in Eucomis regia and investigate whether its floral scent differs markedly from fly‐ and wasp‐pollinated congeners and attracts mammals.We measured floral traits of E. regia and made comparisons with insect‐pollinated congeners. We observed floral visitors and examined fur and faeces of live‐trapped mammals for pollen. We determined the contributions of different floral visitors to seed set with selective exclusion and established the breeding system with controlled pollination experiments. Using bioassays, we examined whether mammals are attracted by the floral scent and are effective agents of pollen transfer.Eucomis regia differs from closely related insect‐pollinated species mainly in floral scent, with morphology, colour and nectar properties being similar. We found that mice and elephant‐shrews pollinate E. regia, which is self‐incompatible and reliant on vertebrates for seed production. Mammals are strongly attracted to the overall floral scent, which contains unusual sulphur compounds, including methional (which imparts the distinctive potato‐like scent and which was shown to be attractive to small mammals).The results highlight the important role of scent chemistry in shifts between insect and mammal pollination systems. [ABSTRACT FROM AUTHOR]

Abstract: How do many species coexist within a trophic level? Resource niches are the classical answer, but in plants which share a small set of abiotic resources, the possibilities for resource partitioning are limited. One possible explanation is that plant species have different pollination niches, with each species specialized to a subset of the available animal species. If this pollinator partitioning results in negative frequency dependence such that each plant species’ reproduction is reduced when it becomes abundant, pollination niches could maintain plant diversity, provided that the strength of negative frequency dependence is sufficient to overcome fitness inequalities between species. We tested this idea by quantifying the effect of species relative abundance on pollinator visitation rate in a 7,000 m2 plot of South African Fynbos vegetation. In addition, we quantified the effect of intraspecific abundance variation at a smaller spatial scale (9 m2 plots), documented species’ pollination niches, and tested the importance of pollinators for seed set in a subset of the plant species. We found that visitation rate indeed declined sharply across the 33 plant species with increasing abundance, but visitation rate was also somewhat depressed in very rare species such that the resulting relationship between visitation rate and relative abundance was hump‐shaped. Pollinator niche partitioning among plant species was evident, but less pronounced than in many other studies. Visitation rate was slightly higher in more generalized species, suggesting that they have access to a larger pollination resource. At the intraspecific level and smaller spatial scale, results were less clear and varied among species. Pollinators enhanced seed set in most species. Synthesis. The results imply that, above an abundance threshold, intraspecific competition for pollination could limit the reproduction of common species, thus promoting plant species coexistence. However, the rarest plant species could become extinct due to pollen limitation, that is, an Allee effect. In addition, interactions with pollinators may introduce frequency‐independent fitness differences between plant species, thereby increasing the strength of negative frequency dependence required for stable coexistence. These findings shed new light on the role of the pollination niche in plant coexistence. [ABSTRACT FROM AUTHOR]

Abstract: The worldwide loss of top predators from natural and agricultural systems has heightened the need to understand how important they are in controlling herbivore abundance. The effect of top predators on herbivore species is likely to depend on (1) the importance of the consumption of intermediate predators by top predators (intra‐guild predation; IGP), but also on (2) plant specificity by herbivores, because specialists may defend themselves better (enemy‐free space; EFS). Insectivorous birds, as top predators, are generally known to effectively control herbivorous insects, despite also consuming intermediate predators such as spiders, but how this effect varies among herbivore species in relation to the cascading effects of IGP and EFS is not known. To explore this, we excluded birds from natural fynbos vegetation in South Africa using large netted cages and recorded changes in abundance relative to control plots for 199 plant‐dwelling intermediate predator and 341 herbivore morpho‐species that varied in their estimated plant specificity. We found a strong negative effect of birds on the total abundance of all intermediate predators, with especially clear effects on spiders (strong IGP). In contrast with previous studies, which document a negative effect of birds on herbivores, we found an overall neutral effect of birds on herbivore abundance, but the effect varied among species: some species were negatively affected by birds, suggesting that they were mainly consumed by birds, whereas others, likely released from spiders by IGP, were positively affected. Some species were also effectively neutrally affected by birds. These tended to be more specialized to plants compared to the other species, which may imply that some plant specialists benefited from protection provided by EFS from both birds and spiders. These results suggest that the response of herbivore species to top predators may depend on cascading effects of interactions among predators and on their degree of plant specificity. [ABSTRACT FROM AUTHOR]

Biological communities are increasingly faced with novel urban habitats and their response may depend on a combination of biological and habitat traits. The response of pollinator species to urban habitats are of particular importance because all species involved in the pollination mutualism may be affected. Nectarivorous bird communities worldwide show varying tolerances to urban areas, but studies from Africa are lacking. We investigated nectarivorous bird communities in a medium‐sized South African city and asked which biological and garden traits best predict the community assembly of specialist and opportunistic nectarivorous birds. Information was collected on garden traits and the frequency of nine nectarivorous bird species for 193 gardens by means of a questionnaire. Information on biological traits of birds was obtained from published literature. Habitat generalism and tree nesting were identified as the most important biological traits influencing bird occurrence in gardens. A greater diversity of indigenous bird‐pollinated plants and the presence of sugar water feeders increased the numbers of nectar specialist birds and species richness of nectarivorous birds. While bird baths increased the species richness of nectar specialist birds, opportunistic birds’ urban adjustment was further facilitated by large vegetated areas in gardens and limited by the distance to the nearest natural habitat. In conclusion, though some biological traits and dispersal barriers seem to limit urban adjustment, a combination of natural and artificial nectar resource provisioning could facilitate this adjustment. [ABSTRACT FROM AUTHOR]

Because establishing a new population often depends critically on finding mates, individuals capable of uniparental reproduction may have a colonization advantage. Accordingly, there should be an over-representation of colonizing species in which individuals can reproduce without a mate, particularly in isolated locales such as oceanic islands. Despite the intuitive appeal of this colonization filter hypothesis (known as Baker's law), more than six decades of analyses have yielded mixed findings., We assembled a dataset of island and mainland plant breeding systems, focusing on the presence or absence of self-incompatibility. Because this trait enforces outcrossing and is unlikely to re-evolve on short timescales if it is lost, breeding system is especially likely to reflect the colonization filter., We found significantly more self-compatible species on islands than mainlands across a sample of > 1500 species from three widely distributed flowering plant families (Asteraceae, Brassicaceae and Solanaceae). Overall, 66% of island species were self-compatible, compared with 41% of mainland species., Our results demonstrate that the presence or absence of self-incompatibility has strong explanatory power for plant geographical patterns. Island floras around the world thus reflect the role of a key reproductive trait in filtering potential colonizing species in these three plant families. [ABSTRACT FROM AUTHOR]

656I.657II.658III.660IV.661V.663VI.663VII.664VIII.664665References665 Summary: Baker's law refers to the tendency for species that establish on islands by long‐distance dispersal to show an increased capacity for self‐fertilization because of the advantage of self‐compatibility when colonizing new habitat. Despite its intuitive appeal and broad empirical support, it has received substantial criticism over the years since it was proclaimed in the 1950s, not least because it seemed to be contradicted by the high frequency of dioecy on islands. Recent theoretical work has again questioned the generality and scope of Baker's law. Here, we attempt to discern where the idea is useful to apply and where it is not. We conclude that several of the perceived problems with Baker's law fall away when a narrower perspective is adopted on how it should be circumscribed. We emphasize that Baker's law should be read in terms of an enrichment of a capacity for uniparental reproduction in colonizing situations, rather than of high selfing rates. We suggest that Baker's law might be tested in four different contexts, which set the breadth of its scope: the colonization of oceanic islands, metapopulation dynamics with recurrent colonization, range expansions with recurrent colonization, and colonization through species invasions. [ABSTRACT FROM AUTHOR]

Aim We aimed to produce the first complete pollination network for Africa to test (1) whether South African plants are unusually specialized in their interactions with pollinators, and (2) whether the South African data conform with global patterns of specialization. Location Cederberg, Cape Floristic Region, South Africa (32°04′31.52″ S, 19°04′ 48.42″ E; elevation 320 m). Methods We sampled all plant-pollinator interactions within a 1-ha plot to assemble a network of 62 plant species linked to 217 pollinators species by 10,314 visits. We calculated the standardized Kullback-Leibler distance ( d′) as an estimate of plant and animal specialization, and standardized two-dimensional Shannon entropy (Δ H2′) as an estimate of network-wide specialization. We compared these metrics with those calculated for 58 other networks from across the world. Results In a global context, the South African plant species had an unusually high number of interaction partners (mean = 6.32) while the animal species had unusually few (mean = 1.81). Animal diversity was high relative to plant diversity (network asymmetry = 0.56). Nevertheless, the South African plants, pollinators and network overall were more specialized than any previously studied community (weighted mean d′ plants = 0.824 and animals = 0.807, community Δ H2′ = 0.834), suggesting functional specialization. Overall, specialization was found to increase sharply with latitude in the Southern Hemisphere, whereas no relationship was found in the Northern Hemisphere. Main conclusions The findings that South African plants have a high diversity of pollinators and that specialization of pollination networks increases with latitude in the Southern Hemisphere only are in contradiction to expectations derived from earlier literature. Long-term climatic stability in the Southern Hemisphere might have allowed phenotypic and functional specialization to manifest and persist. [ABSTRACT FROM AUTHOR]

The possession of certain floral traits can determine which insects visit a plant species. If two species possess similar floral traits that determine shared flower visitors, floral traits can be said to mediate plant-plant interactions. Such indirect interactions are important for understanding fundamental relationships of plant communities, such as competition and facilitation but thus far have only been tested within a native community context., We test whether floral-trait similarity can be used to predict interactions between an invasive plant and co-occurring native species in South Africa's Cape Floristic Region. We surveyed flower visitation at invaded and uninvaded plots across four sites and correlated floral-trait similarity between invasive and native species with both invasion impact on native flower visitation and flower visitor overlap of natives and the invasive species., Similarity of all traits (categorical and continuous) and categorical traits alone explained invasion impact (flower visitor overlap) between the native and invasive species. The majority of flower visitor overlap was attributed to the native honeybee Apis mellifera subsp. capensis., This study is the first to show that floral traits can be used to predict novel plant-plant interactions, even amongst ecologically generalized flower visitors and plants and to predict potential impacts of an invasive species on native flowering communities. However, floral traits were not useful for predicting changes in visitation to plant species., Synthesis. Results advance our understanding of the role of plant traits in ecological communities and reveal that they are important in mediating not only plant-pollinator interactions but also plant-plant interactions. Our findings also shed light on invasive-native plant interactions via pollinators and have the potential to predict certain invasion impacts. [ABSTRACT FROM AUTHOR]

There are at least two immediate reasons why it is important to determine the role of biotic interactions, such as pollination, in limiting species distribution ranges. Firstly, if range limits are imposed by biotic factors, current and future distribution ranges might not be constrained by climate. Secondly, if biotic interactions limit the distribution ranges of species, anthropogenic impacts on these interactions are likely to have a major effect on biodiversity. Here we test the role of pollination in limiting plant distributions by studying plant community assembly in a guild of 15 oil-secreting orchids (Coryciinae) along a pollination gradient. In all members of the guild, seed production depends on pollination by the oil-collecting bee Rediviva peringueyi (Melittidae). While the mode of aboveground reproduction is uniform across the guild, the orchid species differ widely in their capacity for belowground clonal reproduction through the formation of bulbils, and hence span a range of predicted dependence on pollination (and subsequent seed set) for population persistence. Pollination rate by R. peringueyi varied across the landscape from 0 to 98% of flowers pollinated. With decreasing pollination, species richness of the orchid guild declined, and species were lost by the successive deletion of the least clonal species. Thus, pollination is shown to act as a biotic filter, excluding non-clonal species from pollinator-poor communities. The findings are consistent with the idea that pollination mutualisms matter ecologically by limiting the distribution of non-clonal plants. Conversely, the results suggest that clonality allows some plant species to escape from the range of their pollinators. [ABSTRACT FROM AUTHOR]

Road traffic is one of the most pervasive forms of anthropogenic disturbance, but its impact on pollination, a potentially sensitive ecosystem process, has not been investigated. Such an assessment is needed in order to evaluate the potential for roadside verges to act as biodiversity refugia and corridors in otherwise transformed landscapes. Here, we document the impact of a two-lane tar road on pollination by birds in the Cape fynbos of South Africa. To do so, we developed a quick and widely applicable method of determining pollination rates in bird-pollinated members of the large genus Erica. Experiments with caged birds showed that the status of the anther ring (broken/perfect) indicated a sunbird visit with 92% accuracy, while field surveys confirmed anther ring status also serves as a proxy for pollen receipt to stigmas. Using this technique we determined pollination rate in Erica perspicua at three distances from the road (0-10, 20-30 and 40-50 m). After controlling for flower colour, robbing rate and plant density, significantly fewer anther rings were disturbed in close proximity to the road. The documented twofold decline in pollination along roadsides could have important implications for the way we view and manage road verges as refugia for species and ecological processes. [ABSTRACT FROM AUTHOR]

Outside their natural range, honeybees ( Apis mellifera) are known to have detrimental effects on indigenous pollinators through exploitative or interference competition, but little is known about the effect of honeybee farming in areas where honeybees occur naturally. In the Cape Floristic Region of South Africa, where honeybees are indigenous, managed hives potentially elevate the abundance of honeybees far above natural levels, but impacts on other floral resource-dependent species have not been studied. Here we use experimental manipulation of honeybee density to test whether honeybee farming affects nectar-feeding birds. We selected the common sugarbush ( Protea repens), utilized by both birds and bees, and analysed the time (before/after) by treatment (control/experiment) interaction to explore changes in bee abundance, nectar availability and bird abundance at three sites. Hive addition increased honeybee abundance in inflorescences of P. repens above expected levels. Despite experimental increase in honeybee numbers, there is no reduction in nectar sugar availability relative to the control areas. Where honeybee density was highest, sugarbird ( Promerops cafer) numbers declined relative to expected, but sunbirds (Nectarinidae) were not affected at any of the sites. We conclude that stocking rates of more than one honey bee per P. repens inflorescence have detrimental effects on bird abundance due to interference, rather than resource competition. [ABSTRACT FROM AUTHOR]

Widespread reports of low pollination rates suggest a recent anthropogenic decline in pollination that could threaten natural and agricultural ecosystems. Nevertheless, unequivocal evidence for a decline in pollination over time has remained elusive because it was not possible to determine historical pollination rates. Here we demonstrate a widely applicable method for reconstructing historical pollination rates, thus allowing comparison with contemporary rates from the same sites. We focused on the relationship between the oil-collecting bee Rediviva peringueyi (Melittidae) and the guild of oil-secreting orchid species (Coryciinae) that depends on it for pollination. The guild is distributed across the highly transformed and fragmented lowlands of the Cape Region of South Africa. We show that rehydrated herbarium specimens of Pterygodium catholicum, the most abundant member of the guild, contain a record of past pollinator activity in the form of pollinarium removal rates. Analysis of a pollination time series showed a recent decline in pollination on Signal Hill, a small urban conservation area. The same herbaria contain historical species occurrence data. We analyzed this data and found that there has been a contemporaneous shift in orchid guild composition in urban areas due to the local extirpation of the non-clonal species, consistent with their greater dependence on seeds and pollination for population persistence. [ABSTRACT FROM AUTHOR]

Why do hummingbirds hover while Old World nectar-feeding birds perch? A unique opportunity to explore this question is presented by the invasion into Africa of a plant adapted for pollination by hovering hummingbirds. Like other hover-pollinated plants of the New World, the flowers of the tree tobacco Nicotiana glauca lack perches and are oriented towards open space. We find that Old World nectarivores, especially the malachite sunbird, Nectarinia famosa, hover 80% of the time when taking nectar from these flowers. They hover for up to 30 s, and are able to sustain this hovering lifestyle in an area where native nectar plants are absent. Nicotiana glauca greatly increases the local abundance of sunbirds compared with uninvaded areas. In turn, flowers visited by sunbirds formed significantly more capsules and set significantly more seed than sunbird-excluded flowers, possibly facilitating the invasion. The results suggest a prominent role for plant, rather than bird traits in determining the occurrence of hover-pollination, begging the question of why plants adapted for hover pollination do not occur outside the New World. [ABSTRACT FROM AUTHOR]

A suspected global decline in pollinators has heightened interest in their ecological significance. In a worst-case scenario, the decline of generalist pollinators is predicted to trigger cascades of linked declines among the multiple specialist plant species to which they are linked, but this has not been documented. I studied a portion of a pollination web involving a generalist pollinator, the oil-collecting bee Rediviva peringueyi, and a community of oil-secreting plants. Across 27 established conservation areas located in the Cape Floral Region, I found substantial variation in the bees’ occurrence in relation to soil type and the successional stage of the vegetation. Anthropogenic declines were detectable against this background of naturally occurring variation: R. peringueyi was absent from small conservation areas (<385 ha) in an urban matrix. In the absence of the bee, seed set failed in six specialist plant species that are pollinated only by R. peringueyi but remained high in a pollination generalist, which had replacement pollinators. The findings are consistent with theoretical predictions of the importance of generalist pollinators in maintaining the structure of pollination webs. [ABSTRACT FROM AUTHOR]

The long-standing notion of pollination syndromes, which postulates that plants form recognizable groups according to pollinator type, has been challenged recently on the basis of apparent widespread generalization in pollination systems. As a test of the pollination syndrome concept. I examined the pollination biology of a group of 15 orchids that share a recognizable syndrome of floral features that includes yellow-green coloration, oil secretion, pungent scent, shallow flowers, and a September peak in flowering. The orchids occur in sympatry in the Cape Floral Region of South Africa. According to the pollination syndrome concept, the similar floral features of this group indicate a shared pollinator. To test this prediction, I observed pollinators on Pterygodium alatum, P. caffrum, P. catholicum, P. volucris, Corycium orobanchoides, and Disperis bolusiana subsp, bolusiana. They shared a single species of pollinator, the oil-collecting bee, Rediviva peringueyi. Female bees collected oil from the lip appendage using modified front tarsi. The orchids reduce interspecific reproductive interference through differences in pollinarium length or the use of mutually exclusive pollinarium attachment sites on the body of the bee. The results are contrary to the expectation of generalization in pollination systems and suggest that pollinators play an important role in mediating selection on floral traits. [ABSTRACT FROM AUTHOR]

A new kind of stylar polymorphism, provisionally called inversostyly, is described. The polymorphism occurs in Hemimeris racemosa (Scrophulariaceae), a common annual herb of the Cape region of South Africa. Most populations are dimorphic for style orientation: the style alternates with the two stamens and is deflected either upwards or downwards. Thus, there is reciprocal placement of the style and stamens in a vertical plane in zygomorphic flowers. The flowers are symmetrical, and the floral parts do not vary in length. All flowers on a given plant are of the same stylar orientation. Pollination is by specialized oil-collecting bees (Rediviva spp.), which carry the pollen of the two morphs separately in discrete anterior or posterior locations on the underside of the body. Most inversos-tylous populations have a slightly higher proportion of the style-down morph, and this bias increases with decreasing pollinator abundance. In contrast with inversos-tylous populations, all individuals in homostylous populations of H. raceniosa have the style and the stamens clustered together in the down position and high levels of autogamous seed set. Homostylous populations of H. racemosa, as well as the homostylous species Hemimeris sabulosa, occur where oil-collecting bees are less abundant. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the role of rodents in the pollination of the African lily Massonia depressa. Background on studies on the pollination of flowers by rodents; Methodology; Results and discussion.

Abstract: The role of competition in structuring plant communities has recently entered a new phase by considering interactions with pollinators. In this issue of Journal of Vegetation Science, Fantinato et al. show that co‐occurring grassland plants tend to use different pollinators or diverge in anther morphology. The study opens the door for investigation of the ecological and evolutionary processes that generate this pattern. [ABSTRACT FROM AUTHOR]

Aim Reproductive traits are important mediators of establishment and spread of introduced species, both directly and through interactions with other life-history traits and extrinsic factors. We identify features of the reproductive biology of Australian acacias associated with invasiveness. Location Global. Methods We reviewed the pollination biology, seed biology and alternative modes of reproduction of Australian acacias using primary literature, online searches and unpublished data. We used comparative analyses incorporating an Acacia phylogeny to test for associations between invasiveness and eight reproductive traits in a group of introduced and invasive (23) and non-invasive (129) species. We also explore the distribution of groups of trait 'syndromes' between invasive and non-invasive species. Results Reproductive trait data were only available for 126 of 152 introduced species in our data set, representing 23/23 invasive and 103/129 non-invasive species. These data suggest that invasives reach reproductive maturity earlier (10/13 within 2 years vs. 7/26 for non-invasives) and are more commonly able to resprout (11/21 vs. 13/54), although only time to reproductive maturity was significant when phylogenetic relationships were controlled for. Our qualitative survey of the literature suggests that invasive species in general tend to have generalist pollination systems, prolific seed production, efficient seed dispersal and the accumulation of large and persistent seed banks that often have fire-, heat- or disturbance-triggered germination cues. Conclusions Invasive species respond quicker to disturbance than non-invasive taxa. Traits found to be significant in our study require more in-depth analysis involving data for a broader array of species given how little is known of the reproductive biology of so many taxa in this species-rich genus. Sets of reproductive traits characteristic of invasive species and a general ability to reproduce effectively in new locations are widespread in Australian acacias. Unless there is substantial evidence to the contrary, care should be taken with all introductions. [ABSTRACT FROM AUTHOR]