Spatial distribution of nectar production in a natural Echium vulgare population: Implications for pollinator behaviour

The distribution of trait values in many populations is not homogenous but creates a mosaic of patches. This may lead to differences in selection on the patch level compared to selection on the population level. As an example we investigated the spatial distribution of nectar production and its effects on pollinator behaviour in a natural population of Echium vulgare. Nectar production per flower, number of flowers and total nectar production showed a hierarchy and spatial aggregation as expressed by Gini coefficients and significant Moran's I values. Plants in patches of high nectar production received significantly more pollinator visits and had a significant emanating effect on pollinator visits of neighbouring plants. The same was true for plants in patches with high number of flowers. To disentangle these effects a path analysis was applied, which suggested that the direct effect of nectar production per flower although present, seems to be small compared to the effect of the number of flowers. Nectar production per flower affected pollinator visits mainly indirectly by way of total nectar production, which includes the effect of number of flowers. Assuming a minor pollinator-mediated selection for number of flowers, pollinator-mediated selection for total nectar production equals that for nectar production per flower. If so, the observed spatial structure of nectar production and its emanating effect on pollinator behaviour is of importance for natural selection. Plants of low nectar production occurring close to patches of plants with high nectar production benefited from the enhanced pollinator service of their neighbours while saving costs of increased nectar production. Consequently, plants with low nectar production may have a selective advantage at patch level while plants with high nectar production may have a selective advantage at population level. Results presented stress the importance of small-scale patterns for ecological relationships and evolutionary change.     

Quantifying the canopy nectar resource and the impact of logging and climate in spotted gum Corymbia maculata forests

Nectar in tall forest canopies is a significant, but unquantified resource for Australian fauna. We investigated the impact of logging on nectar production in the canopy of spotted gum Corymbia maculata in southern New South Wales. In addition, we quantified the magnitude of canopy nectar production and how this varied with climate over 2 years. In 2005 flowers were bagged on large and small trees in replicate recently logged, regrowth and mature forest. Neither logging history nor tree size significantly affected overnight nectar production per flower, although there was a significant interaction. When nectar production was scaled up to the forest stand (incorporating flower and tree density) mature forest produced almost 10 times as much sugar per ha as recently logged forest, with regrowth being intermediate. Under current forest practices at the compartment scale, the difference between mature forest and recently logged forest was reduced to a factor of two times. One distinctive characteristic of C. maculata nectar in 2005 was its high sugar content (40–60%) compared with the concentrations measured in 2003 (～18%). Nectar was only slightly depleted in unbagged flowers in 2005 when flowering was unusually extensive. We estimated that, on average, mature spotted gum forest produced a vast resource of nectar overnight: 35 000 Kj ha^?1. Flowers measured in 2003 provided a strong contrast with only occasional stands of trees flowering, much less sugar per flower early in the morning and unmeasurable quantities by mid‐morning, indicating that nectar was limiting. Measurements at sites in 2003 indicated that regrowth sites could be more productive than mature forest; however, few sites were measured. We suggest that management should focus mitigations on poor flowering years when the nectar resource is limiting. Models of nectar production collated over both years, using climate and site variables, indicated nectar volumes and sugar concentration respond differently to environmental conditions. Predicting the nectar resource, which is made up of both components, was most consistently related to recent conditions that were unfavourable to foliage production.     

Visual signalling of nectar‐offering flowers and specific morphological traits favour robust bee pollinators in the mass‐flowering tree Handroanthus impetiginosus (Bignoniaceae)

Mass flowering is a widespread blooming strategy among Neotropical trees that has been frequently suggested to increase geitonogamous pollination. We investigated the pollination ecology of the mass‐flowering tree Handroanthus impetiginosus, addressing its breeding system, the role in pollination of different visitors, the impact of nectar robbers on fruit set and the function of colour changes in nectar guides. This xenogamous species is mainly pollinated by Centris and Euglossa bees (Apidae) seeking nectar, which are known to fly long distances. The flowers favour these bees by having: (1) a closed entrance in newly opened flowers which provides access only to strong bees capable of deforming the flower tube; and (2) a nectar chamber that is accessible only to long‐tongued bees. Only first‐day flowers with yellow nectar guides produce nectar. Pollinators prefer these flowers over second‐ and third‐day flowers with orange and red nectar guides, respectively. Nectar robbers damage two‐thirds of the flowers and this robbing activity decreases fruit set by half. We attribute the low fruit set of H. impetiginosus to the intense nectar robbing and hypothesize that visual signalling of nectar presence in newly opened (receptive) flowers reduces geitonogamy by minimizing bee visits to unrewarding (non‐receptive) flowers. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 396–407.     

Synchronized dichogamy and dioecy in neotropicalLauraceae

In hermaphrodite neotropicalLauraceae a highly evolved dichogamous system is present which represents a kind of temporal dioecy. This system involves the existence of two flower morphs which are characterized by reciprocal phases of receptivity of the stigmas and pollen release. In some genera (Persea, Cinnamomum), nectar is produced as a reward for the flower visitors, while in other genera (Aniba, Clinostemon, Licaria), nectar is absent and pollen seems to be the only reward. This implies that in this case the flowers in the female stage must be deceptive flowers. In dioecious species of the generaOcotea andNectandra, both the male and female flowers attract the visitors with nectar. The pollen-ovule ratio of theLauraceae is comparatively low. — The type of reproductive system that characterizes theLauraceae, comprising functional dioecy, small, inconspicuously coloured flowers, pollination by small bees, and large, one-seeded fruits dispersed by birds, is quite prominent among trees of various families in the tropical lowland forest. The relationship between the different modes of flowering within theLauraceae and the causes for the correlation of their reproductive traits are discussed.     

Monitoring seed dispersal at isolated standing trees in tropical pastures: consequences for local species availability

The tropical rain forest landscape has been transformed to a mosaic composed of patches of crops, secondary vegetation and remnant forest fragments of different shapes and sizes. Isolation of patches and fragments is a critical issue in the maintenance of local species diversity. In this study we focus on the dispersal of propagules by birds to understant the movement of plants between landscape components. Seed deposition and the behavior of frugivorous birds were monitored at four isolated fig trees (Ficus yoponensis and F. aurea) in man-made pastures. Seed deposition was measured by trapping seeds under canopy trees for six months and by direct observation of bird visits to the four trees for one year. Seed deposition densities were 465, 614, 632 and 1097 seeds/m² accumulated over six months under each of the four trees. We recorded 8268 seeds of 107 species under the trees, among them, 6726 seeds (81%) were of 56 species dispersed by vertebrate frugivores. Seeds of tree species accounted for 26% of the total species. Seventy-three species of birds perched in the observed trees, and 3344 visits were made by 47 species of frugivores. Frugivorous birds occurred in two groups: resident species nesting in the pastures and resident species nesting elsewhere. Propagule exchange between landscape components is clearly influenced by the behavior of these two groups. Structure and dynamics of the landscape depend on plant species availability within the mosaic. This availability is high and suggests possibilities for the management of the local species diversity of tropical rain forests.     

FLORAL BIOLOGY AND BREEDING SYSTEM OF BAUHINIA BENTHAMIANA TAUB. (LEGUMINOSAE), A BAT-POLLINATED TREE IN VENEZUELAN “LLANOS”

The breeding system and floral characteristics of Bauhinia ungulata L. were investigated during two consecutive flowering cycles (Dec-Feb). This tree grows in savannas in small sized patches scattered in the grassland and in larger tree clusters called “mata.” Anthesis occurs between 17:00 and 19:30. Anther dehiscence and nectar secretion begin one hour after anthesis. Nectar is produced for 10 to 12 hr with an average sugar concentration of 13.5%. Flowers in small trees secrete nectar at a higher rate than do flowers in bigger trees. Two phyllostomatid bat species, Glossophaga soricina and Phyllostomus discolor, visit the flowers of B. ungulata between 20:00 and 4:00. Visits of variable duration occur every 1 to 2 hr. In general, the times of greatest nectar production, of highest solute concentration of the nectar and of most frequent visits by the main pollinators coincide. The flowers are significantly dimorphic in pistil length, and ovules are abortive in the short-pistil flowers. Artificial self- and cross-pollinations in long-and short-pistil flowers show that B. ungulata is genetically self-incompatible and functionally andromonoecious.     

Catching ants with honey: an experimental test of distraction and satiation as alternative modes of escape from flower-damaging ants

According to the distraction hypothesis, extrafloral nectaries (EFN) evolved under selection to entice ants away from floral nectaries, reducing ant-mediated damage to flowers and/or interference with pollinators. Predator-satiation, through production of nectar in either surplus flowers or EFN, provides an alternative mechanism for reducing the impact of ants as flower visitors. I tested these two hypotheses by experimentally adding EFN to flowering plants of the alpine wildflower, Polemonium viscosum, and by surveying the relationship between ant visitation and nectary number in nature. Plants of P. viscosum lack EFN and experience flower damage by ants of Formica neorufibarbus gelida. Ant behavior was compared on plants with five flowers and three experimental EFN and on controls with equal floral display, but no EFN. Addition of EFN increased flower visitation by ants. The effect of EFN on flower visitation did not depend on proximity of EFN to flowers or attractiveness of EFN to ants. Findings suggest that ants perceived patch quality on a whole plant basis, rather than responding to EFN and flowers as distinct nectar patches. Ant visitation did not keep pace with nectary number in nature. The relationship between ant visitation and nectary number per plant was weak and shallow as predicted under satiation. Ant foraging choices on experimental inflorescences showed that ants bypass flowers avoided by earlier ants, enhancing probability of escape via satiation. Results do not support the idea that EFN evolve to reduce flower visitation by ants, but show instead that nectar in surplus flowers can satiate ants and reduce their negative impacts on flower function and integrity.     

Response of avian nectarivores to the flowering of Aloe marlothii : a nectar oasis during dry South African winters

In southern Africa, Aloe marlothii flowers during the dry winter season and offers copious dilute nectar to a variety of birds. Avian abundance and community composition were monitored at an A. marlothii forest at Suikerbosrand Nature Reserve, South Africa. Sampling occurred during two summer months (February–March) when no flowers were present, and six months (May–October) that spanned the winter flowering. We hypothesized that an influx of occasional nectarivores to the A. marlothii forest during flowering would lead to significant changes in the avian community. Overall bird abundance increased 2–3 fold at the peak of nectar availability (August). We recorded 38 bird species, of 83 species detected during transects, feeding on A. marlothii nectar; this diverse assemblage of birds belonged to 19 families, including Lybiidae, Coliidae, Pycnonotidae, Sylviidae, Cisticolidae, Muscicapidae, Sturnidae, Ploceidae and Fringillidae. Surprisingly, only two species of sunbird (Nectariniidae) were observed feeding on A. marlothii nectar, and both occurred in low abundance. We predicted that competition for nectar resources would be high, but few aggressive inter- and intra-specific interactions occurred between birds while feeding on inflorescences. During peak flowering, insect feeders (insectivores, omnivores, nectarivores) fed on nectar during the cold morning when insect activity was low, whilst non-insect feeders (frugivores and granivores) fed on nectar in the middle of the day. Our study highlights the importance of A. marlothii nectar as a seasonal food and water source for a diverse assemblage of occasional nectarivores.     

The Behavior and Interactions of Birds Visiting Erythrina fusca Flowers in the Colombian Amazon1

I observed 22 species of birds visiting flowering Erythrina fusca trees at Matamatá, Amazonas, Colombia. The large orange flowers of E. fusca are adapted for pollination by birds and are protected from illegitimate visits by a petal that covers the nectaries and anthers until displaced by a foraging bird. Experiments with flowers bagged to exclude potential pollinators demonstrated that the flowers do not open without assistance. At Matamatá, parrots are the most frequent visitors to flowering E. fusca, and two species, Dusky‐headed Parakeet (Aratinga weddellii) and Cobalt‐winged Parakeet (Brotogeris cyanoptera), appear to be the main pollinators. This is only the fourth report of Neotropical parrots acting as pollinating agents. At least five other parrot species fed on the nectar or flowers of E. fusca but destroyed the flowers in the process. Orange‐backed Troupials (Icterus jamacaii) were the only other species observed opening E. fusca flowers nondestructively and are likely to be pollinators. Hummingbirds were common visitors to E. fusca flowers and some species were found to carry E. fusca pollen; however, hummingbirds were unable to open the flowers themselves and relied on other visitors to open the flowers for them. The number of hummingbird visits to a flowering E. fusca tree was positively correlated with the number of visits by parrots and icterids, but not with the number of mature flowers, indicating that legitimate visitors facilitate access by hummingbirds.     

Pollination Ecology and Effect of Nectar Removal in Macleania bullata (Ericaceae)1

The floral syndrome of Macleania bullataYeo (Ericaceae) reflects its adaptation to hummingbird pollination. Its flowers, however, are subject to high levels of nectar robbing. I examined the floral visitor assemblage of M. bullata in a tropical montane wet forest in southwestern Colombia, focusing on the behavior of the visitors. I also tested for the presence of nocturnal pollination and the effects of nectar removal on new nectar production. The principal floral visitors were the nectar robbing hummingbirds Ocreatus underwoodii (19.1% of visits) and Chlorostilbon mellisugus (18.9%). Only two species of long–billed hummingbirds visited the flowers of M. bullata as “legitimate” pollinators: Coeligena torquata (14.7% of visits) and Doryfera ludoviciae (14.3%). The remaining visits constituted nectar robbing by bees, butterflies, and other species of hummingbirds. Nocturnal pollination took place, although fruit set levels were 2.4 times higher when only diurnal pollination was allowed as opposed to exclusively nocturnal pollination. Nectar robbers removed floral nectar without pollinating the flower. Treatments of experimental nectar removal were carried out to examine if flowers synthesize more nectar after nectar removal. Nectar removal increased the total volume of nectar produced by each flower without affecting sugar concentration. Thus, nectar robbing can impose a high cost to the plants by forcing them to replace lost nectar.     

The foraging behaviour of a nectar feeding marsupial,Petaurus australis

Summary The foraging behaviour of non-flying nectar feeding mammals has been examined rarely. The exudivorous yellow-bellied glider (Petaurus australis) was observed to feed extensively (70% of the total feeding observation time) on the nectar of all species of Eucalyptus present at a site in southeastern Australia. Gliders harvested nectar, and presumably pollen also, whenever eucalypt flowers were available and selected trees with 2–3 times as many flowers as that on trees randomly selected along a transect. The abundance of flowering trees varied temporally and, at times when few flowering trees were present, gliders chose trees with fewer flowers than at times when flowering trees were abundant. When flowering trees were superabundant or scarce, there was no relationship between the number of flowers in a tree and the duration of visits by gliders. However, at intermediate levels of abundance, the amount of time a glider spent in a tree was related to the number of flowers in a tree. Gliders devoted 90% of the time outside their dens to foraging and the above relationship is suggested to reflect two foraging options which maximize net energy gain for different abundances of flowering trees. Although gliders spent considerable lengths of time in individual trees feeding, initial deposition of cross pollen when gliders first arrive in a tree may be substantial and thus, may provide significant amounts of outcrossing for these eucalypts.     

Flower visitation by birds in Europe

Most flowering plants depend on animal pollination. Several animal groups, including many birds, have specialized in exploiting floral nectar, while simultaneously pollinating the flowers they visit. These specialized pollinators are present in all continents except Europe and Antarctica, and thus, insects are often considered the only ecologically relevant pollinators in Europe. Nevertheless, generalist birds are also known to visit flowers, and several reports of flower visitation by birds in this continent prompted us to review available information in order to estimate its prevalence. We retrieved reports of flower–bird interactions from 62 publications. Forty‐six bird species visited the flowers of 95 plant species, 26 of these being exotic to Europe, yielding a total of 243 specific interactions. The ecological importance of bird–flower visitation in Europe is still unknown, particularly in terms of plant reproductive output, but effective pollination has been confirmed for several native and exotic plant species. We suggest nectar and pollen to be important food resources for several bird species, especially tits Cyanistes and Sylvia and Phylloscopus warblers during winter and spring. The prevalence of bird flower‐visitation, and thus potential bird pollination, is slightly more common in the Mediterranean basin, which is a stopover to many migrant bird species, which might actually increase their effectiveness as pollinators by promoting long‐distance pollen flow. We argue that research on bird pollination in Europe deserves further attention to explore its ecological and evolutionary relevance.     

Small but attractive: female‐biased nectar production and floral visitors in a dimorphic shrub

• In sexually dimorphic species, hermaphrodite flowers in gynodioecious species or male flowers in dioecious species are often larger and produce more nectar than their conspecific female flowers. As a consequence, hermaphrodite or male flowers frequently receive more pollinator visits.
• Sex ratio, flower size, floral display, nectar production and floral visits were evaluated in two natural populations of Fuchsia thymifolia, a morphologically gynodioecious but functionally subdioecious insect‐pollinated shrub.
• Sex ratio did not differ from the expected 1:1 in the two studied populations. As expected, hermaphrodite flowers were larger than female flowers, but in contrast to the general pattern, hermaphrodite flowers did not produce nectar or produced much less than female flowers. Flower visitors were flies (68%) and bumblebees (24%), both of which showed a preference for female flowers. No sex difference was detected in either flower longevity or floral display across the flowering season.
• Higher nectar production by females may attract more pollinators, and may be a strategy to enhance female reproductive success in this species. Finally, floral dimorphism and insect preferences did not seem to hamper the maintenance of sub‐dioecy or prevent the evolution of dioecy in F. thymifolia.

     

Visitation rate of pollinators and nectar robbers to the flowers and inflorescences of Tabebuia aurea (Bignoniaceae): effects of floral display size and habitat fragmentation

Large floral displays favour pollinator attraction and the import and export of pollen. However, large floral displays also have negative effects, such as increased geitonogamy, pollen discounting and nectar/pollen robber attraction. The size of the floral display can be measured at different scales (e.g. the flower, inflorescence or entire plant) and variations in one of these scales may affect the behaviour of flower visitors in different ways. Moreover, the fragmentation of natural forests may affect flower visitation rates and flower visitor behaviour. In the present study, video recordings of the inflorescences of a tree species (Tabebuia aurea) from the tropical savannah of central Brazil were used to examine the effect of floral display size at the inflorescence and tree scales on the visitation rate of pollinators and nectar robbers to the inflorescence, the number of flowers approached per visit, the number of visits per flower of potential pollinators and nectar robbers, and the interaction of these variables with the degree of landscape disturbance. Nectar production was quantified with respect to flower age. Although large bees are responsible for most of the pollination, a great diversity of flower insects visit the inflorescences of T. aurea. Other bee and hummingbird species are highly active nectar robbers. Increases in inflorescence size increase the visitation rate of pollinators to inflorescences, whereas increases in the number of inflorescences on the tree decrease visitation rates to inflorescences and flowers. This effect has been strongly correlated with urban environments in which trees with the largest floral displays are observed. Pollinating bees (and nectar robbers) visit few flowers per inflorescence and concentrate visits to a fraction of available flowers, generating an overdispersed distribution of the number of visits per inflorescence and per flower. This behaviour reflects preferential visits to young flowers (including flower buds) with a greater nectar supply.     

Studies on ecology and behavior of Japanese black swallowtail butterflies. 6. Nectar feeding ofPapilio helenus nicconicolens Butler andP. protenor demetrius Cramer as main pollinators of glory bower,Clerodendron trichotomum,Thunb

The butterfliesPapilio helenus andP. protenor were shown to feed mainly on the nectar of the glory bower,Clerodendron trichotomum, which was the most abundant nectar plant in summer in the study area. Both the species were found to have a proboscis longer than 24 mm corresponding to the length of the corolla tube ofC. trichotomum. Visits to the flowers by these butterflies were observed more frequently than visits by sphingid moths which had previously been believed to be the major pollinators ofC. trichotomum. The male butterflies visited trees ofC. trichotomum frequently, while visits by the females were less frequent. However, once females had visited the tree ofC. trichotomum, they remained there longer than the males. Since the flower ofC. trichotomum has long protruding sexual organs, its pollen grains were found to adhere efficiently to the bodies of butterflies, mainly the thorax, during nectar feeding. Most of the butterflies became loaded withC. trichotomum pollen, and the mean number of pollen grains per butterfly was 1,776 forP. helenus and 2,817 forP. protenor. The flowers opened at any time of day but more frequently in the morning. The nectar was secreted throughout the day. In the maturation of the protandrous flower ofC. trichotomum, the duration of the pistillate phase was about twice as long as the staminate phase. The long flowering period and the short duration of the staminate phase resulted in asynchrony of the flowering stages even within a single cyme on a tree. Such asynchrony and the abundance of attractive flowers on a tree facilitates efficient pollination by the butterflies.     

Competition for bumblebee visitation between Melampyrum pratense and Viscaria vulgaris with healthy and Ustilago-infected flowers

Summary We studied bumblebee foraging on two sympatrically and simultaneously flowering species, Melampyrum pratense (Scrophulariaceae) and Viscaria vulgaris (Caryophyllaceae) during the flowering season of Viscaria in south-west Sweden. We distinguished between healthy and Ustilago-infected Viscaria plants. Both species shared the main insect visitor, queens of Bombus hortorum, which collected nectar from both species but pollen from Melampyrum only. The pattern of visitation changed over the season: bumblebees preferred Viscaria early on, but changed to Melampyrum later in the season, probably because of the higher sugar content of Melampyrum nectar and the possibility of collecting both nectar and pollen from the same flower. Pollen collecting is probably of increasing importance since the need of pollen for the developing larvae will increase with time. Flowers of Viscaria received fewer visits in plots with other species than in pure Viscaria plots during one year and received more visits early than late in the season during both years. Melampyrum flowers received similar amounts of visits in mixed and pure environments. They also received more visits early than late, although this was probably a result of pollinator satiation since Melampyrum became very abundant with time. Ustilago-infected plants received far fewer visits but because of its long flowering time the proportion of open flowers receiving visits was still high. Viscaria flowers received significantly more visits than flowers of other species when bumblebees made heterospecific flower visits from Ustilago-infected plants; thus Ustilago spores were probably effectively dispersed from infected to healthy plants by the pollinators. The mechanism behind competition for pollination in this system was competition through pollinator preference, since the visitation rate to Viscaria actually decreased, but also competition through improper pollen transfer (grains of both species were found on the bodies of bumblebees) since the incidence of switching between the two species increased, probably resulting in an increased misplacement of conspecific pollen grains with time.     

Risk‐averse inflorescence departure in hummingbirds and bumble bees: could plants benefit from variable nectar volumes?

Most hermaphroditic, many-flowered plants should suffer reduced fitness from within-plant selfing (geitonogamy). Large inflorescences are most attractive to pollinators, but also promote many flower visits during a single plant visit, which may increase selfing and decrease pollen export. A plant might avoid the negative consequences of attractiveness through modification of the floral display to promote fewer flower visits, while retaining attractiveness. This report shows that increasing only the variance in nectar volume per flower results in fewer flower visits per inflorescence by wild hummingbirds ( Selasphorus rufus ) and captive bumble bees ( Bombus flavifrons ) foraging on artificial inflorescences. Inflorescences were either constant (all flowers contained the same nectar volume) or variable (half the flowers were empty, the other half contained twice as much nectar as in the constant flowers). Both types of inflorescence were simultaneously available to foragers. Risk-averse foraging behaviour was expressed as a patch departure preference: birds and bees visited fewer flowers on variable inflorescences, and this preference was expressed when resource variability could be determined only by concurrent sampling. When variance treatments were clearly labelled with colour and offered to hummingbirds, the departure effect was maintained; however, when preference was measured by inflorescence choice, birds did not consistently prefer to visit constant inflorescences. The reduced visitation lengths on variable inflorescences by both birds and bees documented in this study imply that variance in nectar production rates within inflorescences may represent an adaptive trait to avoid the costs of geitonogamy.     

A Field Study of Spatial Memory in Green-Backed Firecrown Hummingbirds (Sephanoides sephaniodes)

The foraging ecology of hummingbirds involves the exploitation of a high number of patchily distributed flowers. This scenario seems to have influenced capabilities related to learning and memory, which help to avoid recently visited flowers and to allocate exploitation to the most rewarding flowers, once learning has occurred. We carried out two field experiments with the green‐backed firecrown hummingbird (Sephanoides sephaniodes, Trochilidae) in order to examine the ability of birds, first, to recall a nectar location, and secondly, to remember the location of the most rewarding flower among lower quality flowers. The first experiment showed that subjects were able to recall the location of nectar among flowers of identical appearance. In the second experiment, hummingbirds were also able to recall the location of the most rewarding nectar among less rewarding flowers with the same appearance. The results of this study suggest that S. sephaniodes can remember the location of the most rewarding patch, facilitating efficient exploitation of flowers in the absence of visual cues related to nectar quality.     

Competition versus facilitation: conspecific effects on pollinator visitation and seed set in the iris Lapeirousia oreogena

Ecological interactions between conspecific plants can range from facilitative to competitive depending on the spacing and abundance of individuals. Competitive interactions are expected when plants flower en‐masse and availability of pollinators is limited. We tested this prediction using Lapeirousia oreogena, a mass‐flowering South African iris that is pollinated by a single species of long‐proboscid fly. Controlled hand‐pollination experiments showed that L. oreogena is self‐compatible, but reliant on pollinator visits for seed set. Seed production per flower showed a significant negative relationship with patch size (and the correlated measure of number of individuals per patch), but was not affected by flower density or distance to neighbouring patches. There was a tendency for fly abundance to increase with patch size, but the rate of visits to individual flowers by flies was not affected by patch size. Seed set of hand‐pollinated flowers did not differ for plants in and out of dense patches, indicating that the large differences in seed set among patches were likely to reflect pollinator visits, rather than the genetic or physiological capacity of plants to produce seeds. The reduced fecundity of L. oreogena in large patches with a greater numbers of flowers is consistent with the idea that plants with highly specialized pollination systems can experience intra‐specific competition for pollination.     

Effect of Forest Fragmentation on Tick Infestations of Birds and Tick Infection Rates by Rickettsia in the Atlantic Forest of Brazil

Habitat loss and modifications affect biodiversity, potentially contributing to outbreaks of infectious diseases. We evaluated if the patch sizeinfragmented areas of Atlantic Forest in southeastern Brazil influences the diversity of forest birds and consequently the prevalence of ticks on birds and the rickettsial infection of these ticks. During 2 years, we collected ticks from birds in 12 sites: four small forest patches (80–140 ha), four large ones (480–1,850 ha), and four forest control areas within the much larger Morro do Diabo State Park (~36,000 ha). A total of 1,725 birds were captured (81 species, 24 families), from which 223 birds were infested by 2,339 ticks of the genus Amblyomma, mostly by the species A. nodosum. Bird diversity and richness were higher in larger than smaller forest fragments. The prevalence of ticks on birds was inversely correlated with bird diversity and richness. Among 174 A. nodosum tested for rickettsial infection by polymerase chain reaction, 51 were found to be infected by Rickettsia bellii or Rickettsia parkeri. However, tick infection rates by Rickettsia spp. were not statistically different between forest patch sizes. The higher prevalence of ticks on birds in degraded patches might be caused by a dominance of a few generalist bird species in small patches, allowing an easier transmission of parasites among individuals. It could also be related to more favorable microclimatic conditions for the free-living stages of A. nodosum in smaller forest fragments.The higher burden of ticks on birds in smaller forest fragments is an important secondary effect of habitat fragmentation, possibly increasing the likelihood of Rickettsia contagion.