Demonstration of pollinator‐mediated competition between two native Impatiens species,Impatiens noli‐tangere and I. textori (Balsaminaceae)

Plant–plant interspecific competition via pollinators occurs when the flowering seasons of two or more plant species overlap and the pollinator fauna is shared. Negative sexual interactions between species (reproductive interference) through improper heterospecific pollen transfer have recently been reported between native and invasive species demonstrating pollination‐driven competition. We focused on two native Impatiens species (I. noli‐tangere and I. textori) found in Japan and examined whether pollinator‐mediated plant competition occurs between them. We demonstrate that I. noli‐tangere and I. textori share the same pollination niche (i.e., flowering season, pollinator fauna, and position of pollen on the pollinator's body). In addition, heterospecific pollen grains were deposited on most stigmas of both I. noli‐tangere and I. textori flowers that were situated within 2 m of flowers of the other species resulting in depressed fruit set. Further, by hand‐pollination experiments, we show that when as few as 10% of the pollen grains are heterospecific, fruit set is decreased to less than half in both species. These results show that intensive pollinator‐mediated competition occurs between I. noli‐tangere and I. textori. This study suggests that intensive pollinator‐mediated competition occurs in the wild even when interacting species are both native and not invasive.     

The relative importance of birds and bees in the pollination of Metrosideros excelsa (Myrtaceae)

Exclusion experiments were used to assess the effect of different pollinator groups on outcrossing and seed production in Metrosideros excelsa. The main study site was Little Barrier Island, New Zealand where indigenous bird and native solitary bees are the main flower visitors. Our results showed that native birds were more important pollinators of M. excelsa than native bees. Seed production was much higher in open pollination than in two exclusion experiments where either birds were excluded and native bees only had access to flowers, or where all pollinators had been excluded. The number of fertile seeds per capsule was 45% higher after open pollination than in treatments with bee visitation only and 28% higher than in treatments where all flower visitors were excluded. Estimated outcrossing rates were significantly higher (t_m = 0.71) for open pollination in the upper canopy (>4 m above‐ground level) where bird visitation is presumed to be more frequent than for a treatment with native bee access only (t_m = 0.40). Our results also suggest that a large proportion of seeds (66%) arise from autonomous self‐pollination when all pollinators are excluded. In four trees of a modified mainland population with predominantly introduced birds and a mixture of introduced and native bees there was no decrease in seed production for the treatment allowing bee access only, indicating that – in contrast to native bees – honeybees may be more efficient pollinators of M. excelsa. Observation of the foraging behaviour of both groups of bees showed that native bees contact the stigma of flowers less frequently than honeybees. This is likely to be a consequence of their smaller body size relative to honeybees.     

Breeding system and thrips (Thysanoptera) pollination in the endangered tree Ocotea porosa (Lauraceae): implications for conservation

Ocotea porosa has been extensively exploited over the past few decades because of the quality of its wood. Today, populations are reduced and the species is now included in the Red List of threatened species by the International Union for Nature Conservation. For conservation and management purposes, it is extremely important that we understand its reproductive ecology. Floral morphology was described based on field and scanning electron microscopic examination. The reproductive system was determined through experimentally controlled pollination along with observations of pollen tube growth. Pollinators were identified through field observations. Flowers of O. porosa are small, shallow, inconspicuous, asynchronous and grouped in inflorescences. This species presented self‐compatibility, but did not reproduce through apomixy and spontaneous self‐pollination was very rare (5%). Despite being monoclinal, flowers were protogynic, and the gynoecium was receptive after the first day of anthesis when the anthers were closed. Spontaneous self‐pollination was avoided by the extrorse position of the anthers of the internal stamens. Frankliniella gardeniae (Thysanoptera) was the only pollinating species observed and, after visiting several asynchronous flowers in the same inflorescence, favors geitonogamy. Together the small distance supposedly achieved by thrips in flight and the small population density of O. porosa can reduce the chances of cross‐pollination in this species. If so, conservation measures must include preservation of the current population and possibly planting to increase population density. This would reduce the distance between individuals and increase genetic variability. Thrips as pollinators must be included in conservation planning for O. porosa.     

Delayed autonomous self‐pollination in two Japanese varieties of Epipactis helleborine (Orchidaceae)

The terrestrial orchid Epipactis helleborine is a morphologically variable species with a wide geographical distribution. It is found throughout Europe and continues eastwards to Siberia, China and Japan. It is usually pollinated by social wasps and displays the morphological characteristics of an outcrossing species. In warm, temperate areas of Japan, E. helleborine often appears in alpine or subalpine regions, and has never been found in low‐altitude forests, except for coastal pine forests. The coastal population of E. helleborine is often classified at the variety level, as E. helleborine var. sayekiana, and the inland populations are known as E. helleborine var. papillosa. It is possible that E. helleborine var. sayekiana possesses a distinctive selfing strategy, as its autonomous self‐pollination has evolved in dry habitats, such as coastal dunes. The present study investigated the pollination biology of E. helleborine var. sayekiana and var. papillosa to detect differences in their reproductive systems. Unexpectedly, both E. helleborine var. papillosa and E. helleborine var. sayekiana were found to possess a self‐pollination strategy and were therefore rarely visited by insects. Self‐pollination occurs at the end of the flowering season and probably acts to ensure pollination even if insect‐mediated pollination fails. Moreover, there are no floral differences between E. helleborine var. papillosa and E. helleborine var. sayekiana. These observations suggest that it is not necessary to distinguish between these two varieties. Furthermore, E. helleborine var. papillosa was pollinated by hoverflies, suggesting that E. helleborine var. papillosa is probably biologically distinct from its mother species, E. helleborine. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 733–743.     

Floral scent composition predicts bee pollination system in five butterfly bush (Buddleja,Scrophulariaceae) species

Traditionally, plant–pollinator interactions have been interpreted as pollination syndrome. However, the validity of pollination syndrome has been widely doubted in modern studies of pollination ecology. The pollination ecology of five Asian Buddleja species, B. asiatica, B. crispa, B. forrestii, B. macrostachya and B. myriantha, in the Sino‐Himalayan region in Asia, flowering in different local seasons, with scented inflorescences were investigated during 2011 and 2012. These five species exhibited diverse floral traits, with narrow and long corolla tubes and concealed nectar. According to their floral morphology, larger bees and Lepidoptera were expected to be the major pollinators. However, field observations showed that only larger bees (honeybee/bumblebee) were the primary pollinators, ranging from 77.95% to 97.90% of total visits. In this study, floral scents of each species were also analysed using coupled gas chromatography and mass spectrometry (GC‐MS). Although the five Buddleja species emitted differentiated floral scent compositions, our results showed that floral scents of the five species are dominated by substances that can serve as attractive signals to bees, including species‐specific scent compounds and principal compounds with larger relative amounts. This suggests that floral scent compositions are closely associated with the principal pollinator assemblages in these five species. Therefore, we conclude that floral scent compositions rather than floral morphology traits should be used to interpret plant–pollinator interactions in these Asian Buddleja species.     

Pollination in Lilium sargentiae (Liliaceae) and the first confirmation of long‐tongued hawkmoths as a pollinator niche in Asia

The geographical distribution of pollinators is an important factor determining the biogeographical pattern of floral evolution and diversification. In Africa, a guild of plant species has converged in a floral syndrome for pollination by long‐tongued hawkmoths (predominantly Agrius convolvuli). It is hypothesized that such floral convergence could track the geographical distribution of long‐tongued hawkmoths, so it may not be confined to Africa. We investigated the pollination biology of Lilium sargentiae E. H. Wilson, which is endemic to China and exhibits traits suggestive of long‐tongued hawkmoth pollination. Lilium sargentiae was visited by A. convolvuli as well as small beetles (Nitidulidae) but pollination was mostly or totally effected by the moth. It was consistent with other hawkmoth‐pollinated plants in terms of floral tube length, nectar traits, tepal reflectance, and scent composition. We present the first experimental evidence for the hypothesis proposed above and for hawkmoth pollination in the widespread and ornamentally and economically important genus Lilium L. in a natural habitat. Our findings imply that long‐tongued hawkmoths (especially the extremely widespread A. convolvuli) as a distinctive pollinator niche may have underlain the evolution of long‐tubed (>8 cm) flowers across different continents.     

The snail Smaragdia bryanae (Neritopsina,Neritidae) is a specialist herbivore of the seagrass Halophila hawaiiana (Alismatidae,Hydrocharitaceae)

Abstract. The endemic Hawaiian gastropod Smaragdia bryanae is a specialized marine herbivore that uses the endemic seagrass Halophila hawaiiana as both food and habitat. These small neritids, their grazing scars, and their egg capsules are found year‐round on seagrass leaves, where they feed on protoplast contents released as the sharp outer‐lateral teeth of the snail's radula puncture leaf epidermal cells; the contents of these cells are likely swept into the mouth by the long, wispy cusps of the marginal teeth. Structural differences from the typical neritid radula include elongated outer‐lateral teeth with two sharply pointed cusps, delicate marginal teeth reduced in both size and number, and a compressed central section. Snails grazed on leaves of H. hawaiiana steadily in laboratory culture, and grew and reproduced on this diet. In laboratory choice experiments, snails did not graze the thalli of any of six macroalgal species growing near seagrass where snails were collected, and strongly preferred occupying seagrass. Seagrass samples from five field sites on Oahu and one on Maui showed from 30% to 94% of leaves damaged, with 11% of the total leaf standing area grazed. Snails are smaller (mean length 2.74±0.32 mm, mean width 2.15±0.17 mm, n=217) than the width of the leaves of H. hawaiiana (mean 3.24±1.26 mm, n=790). The snails associate constantly with their host, despite the scattered distribution, small patch size, and variability of the seagrass resource, demonstrated by a sevenfold range in the leaf area index (mean 1.11±0.61 cm² blade surface cm^?2, n=31) among samples. Damage on grazed leaves (mean 8.21±7.05 mm² per leaf, or 16.5% of leaf surface, n=511) is concentrated in the apical and central epithelia between the midrib and the marginal veins, where snails may access cells with thinner walls and few fibers. Details of the grazing interaction between these extant species in Hawai'i shed light on the ecological specialization of members of the genus Smaragdia to seagrasses over geological time.     

Spatial variation in the demography and population dynamics of a perennial shrub (Atriplex vesicaria) under sheep grazing in semi‐arid Australian rangelands

Atriplex vesicaria Heward ex Benth. (Chenopodiaceae) is a widespread perennial shrub in southern Australia's chenopod rangelands but is sensitive to grazing. A detailed investigation of the demography and population dynamics of A. vesicaria under sheep grazing was conducted over 6.5 years at a range of sites across a typical paddock to assess the long‐term effects of grazing on the species and elucidate the mechanisms of population change under grazing. The effects of rainfall on recruitment and mortality were also examined. Six‐monthly censuses of all A. vesicaria individuals were conducted in permanent grazed and ungrazed plots at sites located across an 1100‐ha paddock. Grazing increased adult shrub mortality close to water and reduced recruitment over a broader area of the paddock, but seedling survival did not appear to be affected by grazing. As a result of these changes, the population declined on grazed plots up to 2200 m from water during the study, but the decline was greatest closer to water. The population was most dynamic at the sites furthest from the water point where it was unaffected by grazing because of the greater recruitment and mortality of young plants, but because these processes balanced out over time, population density was effectively unchanged by the end of the study. Although statistical models indicated that six‐monthly rainfall did not explain temporal variation in recruitment or mortality, rainfall nevertheless has a central role in both processes. In particular, longer periods of favourable rainfall and drought appear to have an important influence on recruitment and mortality, respectively, with heavy grazing during a drought period increasing mortality. Occasional shortages of seed or rains occurring during the warmer months when seed germination is limited possibly explain poor recruitment at sites unaffected by grazing following good rainfall.     

Ecological context of breeding system variation: sex, size and pollination in a (predominantly) gynodioecious shrub

BACKGROUND AND AIMS: Species that exhibit among-population variation in breeding system are particularly suitable to study the importance of the ecological context for the stability and evolution of gender polymorphism. Geographical variation in breeding system and sex ratio of Daphne laureola (Thymelaeaceae) was examined and their association with environmental conditions, plant and floral display sizes, and pollination environment in a broad geographic scale was analysed. METHODS: The proportion of female and hermaphrodite individuals in 38 populations within the Iberian Peninsula was scored. Average local temperature and precipitation from these sites were obtained from interpolation models based on 30 years of data. Pollination success was estimated as stigmatic pollen loads, pollen tubes per ovule and the proportion of unfertilized flowers per individual in a sub-set of hermaphroditic and gynodioecious populations. KEY RESULTS: Daphne laureola is predominantly gynodioecious, but hermaphroditic populations were found in northeastern and southwestern regions, characterized by higher temperatures and lower annual precipitation. In the gynodioecious populations, female plants were larger and bore more flowers than hermaphrodites. However, due to their lower pollination success, females did not consistently produce more seeds than hermaphrodites, which tends to negate a seed production advantage in D. laureola females. In the northeastern hermaphroditic populations, plants were smaller and produced 9-13 times fewer flowers than in the other Iberian regions, and thus presumably had a lower level of geitonogamous self-fertilization. However, in a few southern populations hermaphroditism was not associated with small plant size and low flower production. CONCLUSIONS: The findings highlight that different mechanisms, including abiotic conditions and pollinator service, may account for breeding system variation within a species' distribution range and also suggest that geitonogamy may affect plant breeding system evolution.     

Persistence of flower visitors and pollination services of a generalist tree in modified forests

Flower‐visiting insects provide essential pollination services to many plant species. It is thus of critical importance to understand the effects of anthropogenic landscape modification on these animals. Particularly at the landscape scale, we still lack information on how flower visitors are affected by different intensities of human disturbance. In this study, we chose six representative types of forest modification across a heterogeneous South African landscape. At 36 study sites we observed insect visitation to Celtis africana flowers in two consecutive years. This generalist tree species has small unspecialized flowers which we found to be pollinated by a diverse array of insects as well as by wind. Visitation rates to flowers of C. africana differed significantly among the six forest types and between two study years. Visitation rates were enhanced in modified forests, facilitated by a high abundance of feral honeybees (Apis mellifera). Fruit set in C. africana showed significant positive associations with insect visitation and with the diversity of flower visitors, but was only weakly predicted by forest type. Our findings imply that even though forest modification can strongly alter flower visitors, pollination services for trees with unspecialized flowers may persist at a landscape scale. We advise conservation managers to maintain modified forest fragments in addition to natural forests as these may contribute to sustain pollination services in human‐modified landscapes.     

Reproductive biology and pollination ecology of Triplaris gardneriana (Polygonaceae): a case of ambophily in the Brazilian Chaco

• Triplaris gardneriana (Polygonaceae) is a dioecious pioneer tree reported as insect‐pollinated, despite possessing traits related to anemophily. Here, we analyse the possible roles of insects and wind on the pollination of this species to establish whether the species is ambophilous.
• We carried out observations of floral biology, as well as on the frequency and behaviour of pollinators visiting flowers in a population of T. gardneriana in the Chaco vegetation of Brazil. We conducted experimental pollinations to determine the maternal fertility of female plants and whether they were pollen‐limited, and we also conducted aerobiological experiments to provide evidence of how environmental factors influence atmospheric pollen dispersal.
• The population comprised an area of approximately 152.000 m² and was composed of 603 female and 426 male plants (sex ratio = 0.59:0.41). We observed 48 species of insects visiting flowers of T. gardneriana, of which the bees Scaptotrigona depilis and Apis mellifera scutellata were the most effective pollinators. We recorded pollen grains dispersed by wind on 74% of the glass slides placed on females, located at different distances (1–10 m) from male plants.
• Airborne pollen concentration was negatively correlated with relative humidity and positively correlated with temperature. Our observations and experimental results provide the first evidence that T. gardneriana is an ambophilous species, with pollen dispersal resulting from both animal and wind pollination. This mixed pollination strategy may be adaptive in T. gardneriana providing reproductive assurance during colonisation of sites with different biotic and abiotic conditions.

     

Pollinator preference and pollen viability mediated by flower color synergistically determine seed set in an Alpine annual herb

Gentiana leucomelaena manifests dramatic flower color polymorphism, with both blue‐ and white‐flowered individuals (pollinated by flies and bees) both within a population and on an individual plant. Previous studies of this species have shown that pollinator preference and flower temperature change as a function of flower color throughout the flowering season. However, few if any studies have explored the effects of flower color on both pollen viability (mediated by anther temperature) and pollinator preference on reproductive success (seed set) in a population or on individual plants over the course of the entire flowering season. Based on prior observations, we hypothesized that flower color affects both pollen viability (as a function of anther temperature) and pollen deposition (as a function of pollinator preference) to synergistically determine reproductive success during the peak of the flowering season. This hypothesis was tested by field observations and hand pollination experiments in a Tibetan alpine meadow. Generalized linear model and path analyses showed that pollen viability was determined by flower color, flowering season, and anther temperature. Anther temperature correlated positively with pollen viability during the peak of the early flowering season, but negatively affected pollen viability during the peak of the mid‐ to late flowering season. Pollen deposition was determined by flower color, flowering season (early, or mid‐ to late season), and pollen viability. Pollen viability and pollen deposition were affected by flower color that in turn affected seed set across the peak of the flowering season (i.e., when the greatest number of flowers were being pollinated). Hand pollination experiments showed that pollen viability and pollen deposition directly influenced seed set. These data collectively indicate that the preference of pollinators for flower color and pollen viability changed during the flowering season in a manner that optimizes successful reproduction in G. leucomelaena. This study is one of a few that have simultaneously considered the effects of both pollen viability and pollen deposition on reproductive success in the same population and on individual plants.     

Intensified wind pollination mediated by pollen dimorphism after range expansion in an ambophilous biennial Aconitum gymnandrum

Pollination systems and associated floral traits generally differ between core and marginal populations of a species. However, such differences are rarely examined in plants with a mixed wind‐ and bumblebee‐pollination system, and the role of wind pollination during range expansion in ambophilous plants remains unclear. We compared floral traits and the contributions of bumblebee and wind pollination in refugium and marginal populations of the ambophilous plant Aconitum gymnandrum. We found that most floral traits differed between the two populations, and those traits associated with the shift to wind pollination were pronounced in the marginal population. Bumblebee visitation rates varied significantly, but were generally low in the marginal population. Wind pollination occurred in both populations, and the efficiency was lower than that of bumblebee pollination. Two types of pollen grains, namely round and fusiform pollen, were transported to a stigma by bumblebees and wind, but fusiform pollen contributed to wind pollination to a larger degree, especially in the marginal population. Our results suggest that wind pollination was enhanced by pollen dimorphism in the marginal population of A. gymnandrum, and wind pollination may provide reproductive assurance when bumblebee activity is unpredictable during range expansion, indicating that ambophily is stable in this species and shift in pollination system could be common when plants colonize new habitats.     

Abundance drives broad patterns of generalisation in plant–hummingbird pollination networks

Abundant pollinators are often more generalised than rare pollinators. This could be because abundant species have more chance encounters with potential interaction partners. On the other hand, generalised species could have a competitive advantage over specialists, leading to higher abundance. Determining the direction of the abundance–generalisation relationship is therefore a ‘chicken‐and‐egg’ dilemma. Here we determine the direction of the relationship between abundance and generalisation in plant–hummingbird pollination networks across the Americas. We find evidence that hummingbird pollinators are generalised because they are abundant, and little evidence that hummingbirds are abundant because they are generalised. Additionally, most patterns of species‐level abundance and generalisation were well explained by a null model that assumed interaction neutrality (interaction probabilities defined by species relative abundances). These results suggest that neutral processes play a key role in driving broad patterns of generalisation in animal pollinators across large spatial scales.     

Choice,performance and heritability of performance of specialist and generalist insect herbivores towards cacalol and seneciphylline,two allelochemicals of Adenostyles alpina (Asteraceae)

We compared the effects of a sesquiterpene (ST, cacalol) and a pyrrolizidine alkaloid (PA, seneciphylline), both occurring in Adenostyles alliariae, on food choice and performance of specialist and generalist insect herbivores which are all known to feed or live on A. alliariae. In choice experiments we investigated whether the compounds were preferred, deterrent or had no effect. All specialist species Aglaostigma discolor (Hymenoptera, Tenthredinidae), Oreina cacaliae (Coleoptera, Chrysomelidae) and O. speciosissima avoided feeding when confronted with the combination of compounds. Only larvae of A. discolor avoided the single ST treatment as well. Larvae of the generalist species Callimorpha dominula (Lepidoptera, Arctiidae), Cylindrotoma distinctissima (Diptera, Tipulidae) and Miramella alpina (Caelifera, Acrididae) generally avoided feeding from PA, ST and PAST treatments. The only exception were caterpillars of C. dominula which were indiscriminate towards PA when naive, and preferred to feed on the PA treatment when they had experienced the compound before. Performance, measured as the growth of larvae on the different treatments in a no choice situation over a period of 10–17 days, was not different between treatments in the specialist leaf beetles O. cacaliae and O. speciosissima. Their avoidance of the combination treatment in the choice experiments had no obvious effect on growth when forced to feed from the treatment. In the generalist C. dominula only the high concentration combination treatment (PAST) reduced growth of the larvae due to decreased consumption. In C. distinctissima we found reduced growth in all treatments except one (PA3%). Poor growth performance in C. distinctissima was due to postingestive physiological effects of all treatments and additionally to consumption reduction in high‐dose ST treatments. Genetic variability (broad sense heritability) of growth performance metabolism varied in accordance with the specialization degree of the species. O. cacaliae, the most specialized species, had no significant heritability; O. speciosissima, the less specialized specialist, had a heritability of 0.46; C. dominula, the PA adapted generalist species, had a heritability of 0.64; C. distinctissima, the generalist with no apparent adaptations, had a heritability of 0.84.     

Floral biology,reciprocal herkogamy and breeding system in four Psychotria species (Rubiaceae) in Brazil

Distylous species have two floral morphs with reciprocal positions of sexual whorls, functioning to promote cross‐pollination. Additionally, most distylous species have an incompatibility system linked to the discrete variation of anthers and stigmas. Here we provide new data on heterostyly, reproductive biology and pollination in four Psychotria spp. from the Cerrado Region (Brazil). Psychotria deflexa, P. nitidula and P. trichophoroides fitted the distylous morphological syndrome, whereas P. prunifolia was monomorphic and self‐compatible. Reciprocity varied across species, with the upper whorl of anthers and stigmas being more reciprocal than the lower whorl. Psychotria nitidula has a heteromorphic incompatibility system, whereas P. deflexa and P. trichophoroides showed partial self‐compatibility. Psychotria prunifolia and P. trichophoroides were visited by large bees and exhibited lower reproductive efficacy than P. nitidula and P. deflexa, which are visited by wasps and small bees. Our results provide new evidence that the morphological distylous syndrome does not always co‐occur with heteromorphic incompatibility and additional mechanisms (e.g. disassortative pollen transfer) may operate to maintain the polymorphism and isoplethy of species with different incompatibility system.     

Comparative study of pollination biology of two closely related alpine Primula species,namely Primula beesiana and P. bulleyana (Primulaceae)

Abstract The comparative pollination biology of a population of Primula beesiana, a population of P. bulleyana, and an overlapping population of these two species in Yulong Shan, Yunnan Province, China, was studied in 2004 and 2005. The results indicate that both P. beesiana and P. bulleyana are typical heterostylous and obligate outcrossing species; the main pollinators of the two species were bees and butterflies. At the sites of all three populations, the main pollinating visitors of the two species showed preference for one of the two species, resulting in the ethological isolation of the two species by the pollinators. This ethological isolation contributes to the reproductive isolation of the two species, which supports the hypothesis that P. beesiana and P. bulleyana are two distinct species. The reproductive isolation of the two species (ethological isolation) is probably an important mechanism in maintaining species boundaries in the genus and has contributed to the species diversification of Primula in the area. In addition, gene exchanges between P. beesiana and P. bulleyana has occurred to some extent in the overlapping population, but whether natural hybridization has contributed to species diversification in Primula remains to be determined.     

Comparative study of pollination biology of two closely related alpine Primula species,namely Primula beesiana and P.bulleyana (Primulaceae)

The comparative pollination biology of a population of Primula beesiana,a population of P.bulleyana,and an overlapping population of these two species in Yulong Shan,Yunnan Province,China,was studied in 2004 and 2005.The results indicate that both P.beesiana and P.bulleyana are typical heterostylous and obligate outcrossing species;the main pollinators of the two species were bees and butterflies.At the sites of all three populations,the main pollinating visitors of the two species showed preference for one...     

Breeding system and spatial variation in the pollination biology of the heterocarpic Thymelaea velutina (Thymelaeaceae)

Thymelaea velutina (Thymelaeaceae) is a unique dioecious and heterocarpic shrub, each female producing both dry and fleshy fruits. It is endemic to the Balearic Islands (western Mediterranean) and has suffered an important regression in recent decades, especially due to habitat loss. It lives in coastal areas, mainly in dunes, but a few populations occur up to 1300 m in the mountains of Mallorca. In the present study, we examined its breeding system and pollen vectors, determined whether seed production is pollen-limited, and quantified the relative importance of different insect visitors at coastal and mountain sites. Selective exclusions showed no differences between populations in the relative importance of insects and wind as pollen vectors. Pollen was limiting at both populations, though not consistently in time. Flowers of T. velutina were visited mostly by generalist insects, and species composition and abundance of flower visitors varied both in space and time. The flowering period is about a month later in the mountain than in the dune, and this results in a higher frequency of insect visits to plants in the mountain due to the higher insect abundance; insects were also more diverse in the mountain, although they visited a proportionally lower number of flowers than in the dune. Despite this spatio-temporal variation in the frequency of insect visits and in the importance of a particular insect group, the ambophilous system in this species (previously described as anemophilous) ensures a relatively high fruit set at the two different sites.     

Evolutionary disruption in the pollination system of Vanilla (Orchidaceae)

• Pollination of the pantropical Vanilla has been linked to melittophily and food deception.
• Here we investigated the role of flower traits on the reproduction of Neotropical Vanilla. We also studied the evolution of pollination systems in order to understand the origin of production of flower resources and the diversification of pollinators in this orchid genus. Our study was founded on data of adaptations in flower morphology, production of resources, scent release, pollinators and breeding systems of Vanilla and presenting new data on reproductive biology of V. palmarum. Data on reproductive biology of Vanilla were mapped onto a phylogeny to address our queries on the evolution of pollination systems in this genus.
• Vanilla palmarum shows a mixed mating system, with its facultative autogamous flowers being pollinated by hummingbirds. Its yellow flowers are scentless and produces nectar. Mapping of the pollination system onto trees resulted in one origin for bird pollination and at least two origins for autogamy in Vanilla. Nectar secretion has a single origin in the Neotropical thick-leafed lineage.
• Bird pollination of Vanilla is shown for the first time. The origin of ornithophily within a bee-pollinated clade is supported by flower morphology. Floral transitions to ornithophily have been favoured by the occupation of a distinct niche from that of the other thick-leafed Vanilla species. Despite its specialized pollination, V. palmarum is autogamous. A mixed mating system can promote reproductive assurance in the case of a decline in pollinator populations, or in areas where pollinator services are irregular or absent.