Autonomous self‐pollination in the nectarless orchid Pogonia minor

The pollination biology of the nectarless orchid Pogonia minor was investigated in central Japan. The investigation revealed that the solitary flowers failed to attract pollinators, while high rates of fruit set were observed in the natural population. Comparable levels of fruit set were obtained in bagged, artificial self‐pollinated and artificial cross‐pollinated plants, indicating that the species is not pollinator‐limited for fruit set under natural conditions. Autonomous self‐pollination in P. minor resulted from a reduced rostellum, which allowed contact between the pollinia and the stigma. Self‐pollination is thought to be an adaptive response that provides reproductive assurance under conditions of pollinator limitation. Since pollen limitation is generally known to be frequent among deceptive orchids, strong pollen limitation is probably a driving force in the autonomous self‐pollination mechanism in the nectarless orchid P. minor.     

Fly pollination in Cypripedium: a case study of sympatric C. sichuanense and C. micranthum

Most Cypripedium spp. are known to be pollinated by bees. However, myiophilous traits are found in some species, especially in sections Trigonopedia and Sinopedilum. Here we chose C. micranthum and C. sichuanense, two sympatric species endemic to Sichuan, China, to test whether these orchids are fly pollinated. Artificial pollination showed that both flowers are self‐compatible but need pollen vectors for successful reproduction. Field observation showed that C. micranthum was pollinated by fruit flies and C. sichuanense by dung flies, both novel pollinators of Cypripedium orchids. These sympatric Cypripedium spp. are also cross‐compatible, but hybrids were not found in nature. The pollination syndromes of C. sichuanense and C. micranthum fit into the complex sapromyiophily pattern. It appears that pollinator specificity is responsible for their reproductive isolation. The discovery of fly pollination in C. sichuanense and C. micranthum, which belong to the related sections Trigonopedia and Sinopedilum, suggests a shift from bee to fly pollination in the genus Cypripedium. Unlike most Cypripedium spp., the anthers of C. micranthum release discrete pollinia with narrow stalks instead of the usual amorphous pollen smears. This ‘proto‐pollinarium’ is described, probably for the first time. These pollinia are most likely an adaptation for pollination by microdiptera, so the fly can carry the contents of both chambers in the same anther. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170 , 50–58.     

Reproductive biology of Trichocentrum pumilum: an orchid pollinated by oil-collecting bees

The reproductive biology, reward production and pollination mechanism of Trichocentrum pumilum were studied in a gallery forest in the interior of the State of São Paulo, southeast Brazil. The floral visitors and pollination mechanism were recorded, and experimental pollinations were carried out in order to determine the breeding system of this species. Trichocentrum pumilum blooms in spring. Each paniculate inflorescence bears an average of 85 flowers that present a central yellow callus and finger‐like trichomes on the lateral lobes of the lip. A lipoidal substance is produced and stored among these trichomes. In the studied population, T. pumilum is exclusively visited and pollinated by two bee species (Tetrapedia diversipes and Lophopedia nigrispinis). Pollinaria are deposited on mouthparts of bees during collection of the lipoidal substance from the lateral lobes of the labellum. Trichocentrum pumilum is self‐incompatible and pollinator‐limited. Natural fruit set was low (9%, compared to 45% in experimentally cross‐pollinated flowers). Potentially viable seed exceed 97% in fruits obtained through cross‐pollination and in natural conditions (open pollination).     

Reproductive biology and pollination mechanisms of Epidendrum secundum (Orchidaceae). Floral variation: a consequence of natural hybridization?

The phenology, flower morphology, pollination mechanism and reproductive biology of Epidendrum secundum were studied in a semi‐deciduous forest at the Serra do Japi (SJ), and in the Atlantic rain forest of Picinguaba, both natural reserves in the State of São Paulo, southeastern Brazil. E. secundum flowers all year round, with a flowering peak between September and January. This species is either a lithophytic or terrestrial herb in the SJ, whereas, in Picinguaba, it grows mainly in disturbed areas along roadsides. E. secundum is pollinated by several species of diurnal Lepidoptera at both study sites. In Picinguaba, where E. secundum is sympatric with E. fulgens and both share the same pollinators, pollen transference between these two species was recorded. E. secundum is self‐compatible but pollinator‐dependent. It is inter‐compatible with E. fulgens, producing fertile seeds. In contrast to the population of the SJ, in the Picinguaba region, floral morphology is quite variable among plants and some individuals present flowers with characteristics in‐between both sympatric species, suggesting that natural hybridization occasionally occurs. The anthropogenic perturbation is probably the cause of the occurrence of E. secundum in the Picinguaba region, enabling its contact with E. fulgens.     

Evidence for autonomous selfing in grassland Protea species (Proteaceae)

It has been assumed that species of the large African genus Protea have strong self‐incompatibility systems. However, this assumption was based largely on studies conducted on a clade of bird‐pollinated species that occur in the shrubby fynbos vegetation of the Cape region of southern Africa. To test whether self‐incompatibility occurs in a grassland/savanna Protea clade, which is largely insect‐pollinated, we performed controlled pollination experiments on four species, P. caffra, P. dracomontana, P. simplex and P. welwitschii. Although pollen–ovule ratios of all four species fall within the range for outcrossers, all four species are self‐compatible and capable of autonomous seed production. Using fluorescence microscopy, we found that self‐pollen tubes had the same probability of reaching ovules as cross‐pollen tubes. In the small tree P. caffra, selfed progeny had rates of germination and survivorship that were identical to those of crossed progeny. The grassland Protea spp. studied are likely to have mixed mating systems on account of being both visited by insects and capable of autonomous selfing. If one assumes previous reports of self‐incompatibility in Protea to be reliable, there have been at least five losses of self‐incompatibility and two gains of autonomous selfing in this genus. However, earlier studies in the genus were often methodologically flawed and a thorough re‐analysis of breeding systems in Protea is required. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 433–446.     

Pollinator‐independent orchid attracts biotic pollinators due the production of lipoidal substances

• Flowering plants often depend on the attraction of biotic pollinators for sexual reproduction. Consequently, the emergence and maintenance of selected floral attributes related to pollinator attraction and rewarding are driven by pollinator pressure.
• In this paper we explore the effect of pollinators, rainfall, temperature and air humidity on the reproduction of a Brazilian terrestrial orchid, Cranichis candida based on data of phenology, flower resources, olfactory and visual attraction cues, pollinators and breeding system.
• The flowers of C. candida are strongly protandrous and pollinated by workers of the social native bee Tetragonisca angustula. The bees collect labellar lipoidal substances (wax scales), which are transported to the nest. The lipoidal substance is composed of sterols, hydrocarbons and terpenes. The last presumably protects the bees and their nests against pathogens and other arthropods. C. candida sets fruits through biotic self‐ and cross‐pollination, and spontaneously due the action of raindrops on flowers.
• Our results indicate that in C. candida, although rain‐mediated spontaneous self‐pollination happens, fructification mediated by biotic pollinations also occurs, which may result in fruit set by cross‐pollination. A mixed pollination system must result in higher genetic variability when compared to species whose fruits are produced entirely by self‐pollination. On the other hand, autogamy is a form of reproductive assurance, and has commonly evolved where pollination services are rare or absent.

     

Pollination biology of the endangered orchid Cypripedium japonicum in a fragmented forest of Japan

Pollination biology studies of the endangered orchid Cypripedium japonicum were conducted in its natural habitat using pollinator observation and hand‐pollination experiments. The observed fruit set was as follows: artificial outcross‐pollinated, 100%; artificial self‐pollinated, 100%; pollinator‐excluded, 0%; and emasculated flowers, 0%. These results show that this species, although self‐compatible, is neither autogamous nor agamospermous. The fruit set for open‐pollinated flowers was 14.9%, which suggests that the study population was subject to pollinator limitation. The nectarless flowers of C. japonicum were exclusively visited and pollinated by the queens of two bumblebee species (Bombus ardens and B. diversus diversus). It is probable that the nectarless flowers of C. japonicum attract pollinators through a generalized food deceptive system.     

Reproductive biology of a hummingbird‐pollinated Billbergia: light influence on pollinator behaviour and specificity in a Brazilian semi‐deciduous forest

• Ornithophily has evolved in parallel several times during evolution of angiosperms. Bird pollination is reported for 65 families, including Bromeliaceae. One of the most diverse bromeliad is Billbergia, which comprises species pollinated mainly by hummingbirds.
• Based on investigations on flowering phenology, morpho‐anatomy, volume and concentration of nectar, pollinators and breeding system, this paper explores the reproductive biology and pollinator specificity of B. distachia in a mesophytic semi‐deciduous forest of southeastern Brazil.
• The results have show that B. distachia is pollinated by a single species of hermit hummingbird, Phaethornis eurynome, which search for nectar produced by a septal nectary, where the secretory tissue is located above the placenta. The species is self‐incompatible. The combination of pollinator specificity, due to long corolla tubes that exclude visitation of short‐billed hummingbirds, complete self‐incompatibility and non‐territorial behaviour of pollinators, it is very important to reduce pollen loss and increase gene flow within population.
• Our results indicate that studies on pollination biology and reproduction are essential to understand the evolutionary history of pollination systems of plants since, at least in Billbergia, variation in the pollinator spectrum has been recorded for different habitats among Brazilian forests. Furthermore, according to our data, foraging of Phaethornis on flowers is independent of air temperature and humidity, while the main factor influencing hummingbird visitation is daylight. Considering current knowledge on climatic parameters influencing hummingbird foraging, pollination and reproductive biology of Neotropical flora and environment of the hermit hummingbird in tropical forests, new insights on plant–pollinator interaction are provided.

     

Social wasps,crickets and cockroaches contribute to pollination of the holoparasitic plant Mitrastemon yamamotoi (Mitrastemonaceae) in southern Japan

• Mitrastemon yamamotoi is completely embedded within the tissues of its hosts, except during the reproductive stage, when aboveground parts emerge from host tissues. Its highly modified appearance has attracted attention of many botanists, but very little is known about the reproductive system.
• Floral visitors to M. yamamotoi were observed in southern Japan. Pollination experiments were conducted to determine the plant's self‐compatibility and pollen limitation, as well as the contribution of diurnal and nocturnal visitors to fruit set and outcrossing.
• Mitrastemon yamamotoi is mainly pollinated by social wasps, but previously unnoticed pollinators (i.e. crickets and cockroaches) are also important, based on visitation frequency and pollen loads. Results of the pollination experiments suggest that nocturnal visitors, such as crickets and cockroaches, contribute to geitonogamous pollination, whereas diurnal visitors, such as social wasps, facilitate outcrossing.
• The unexpected pollinator assemblage of M. yamamotoi might be influenced by multiple factors, including the highly modified flowers that are produced close to the ground in dark understorey environments, the species’ winter‐flowering habit and the location of the study site (i.e. near the northern limit of the species’ range). Considering that M. yamamotoi occurs widely in subtropical and tropical forests in Asia, additional studies are needed to assess pollinator assemblages of M. yamamotoi at other locations.

     

Experimental evidence for specialized bird pollination in the endangered South African orchid Satyrium rhodanthum and analysis of associated floral traits

The bird pollination syndrome is characterized by red, unscented flowers with dilute nectar in long nectar tubes. However, the extent to which plants with such traits actually depend on birds for seed production is seldom determined experimentally, and traits such as colour and scent production are often assessed only subjectively. We documented bird pollination and quantified floral traits in the critically endangered Satyrium rhodanthum (Orchidaceae) from mistbelt grasslands in the summer‐rainfall region of South Africa. Direct observations and motion trigger camera footage revealed amethyst sunbirds as the only pollinators, despite the presence of other potential pollinators. Experimental exclusion of sunbirds significantly reduced pollination and fruit set to near zero. Pollination success in naturally pollinated plants was close to 100% in one year, and fruit set varied from 23 to 64% in other years. Pollen transfer efficiency was 5.8%, which is lower than in related insect‐pollinated species, probably due to a tendency of birds to wipe pollinaria from their beak. Flowers of S. rhodanthum only reflect light in the red range of the spectrum, and they produce only a few aliphatic and monoterpene scent compounds at comparatively low emission rates. Nectar volume and sugar concentration varied between 2.7 and 3.7 μL and 23.7 and 25.9%, respectively. We conclude that S. rhodanthum is highly specialized for pollination by sunbirds. Colour, scent and nectar characteristics differ from insect‐pollinated Satyrium species and are consistent with those expected for bird‐pollinated flowers, and may contribute to lack of visitation by other potential long‐tongued pollinators. Habitat loss probably underlies the critically endangered conservation status of S. rhodanthum, but the specialization for pollination by a single bird species means that reproduction in this orchid is vulnerable to losses in surrounding communities of plants that subsidize the energetic requirements of sunbirds. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 177 , 141–150.     

Crane flies and microlepidoptera also function as pollinators in Epidendrum (Orchidaceae: Laeliinae): the reproductive biology of E. avicula

Crane flies and microlepidoptera have been recorded as pollinators in unrelated orchid groups, but these insects have never been recorded in Epidendroideae, the most species‐rich orchid subfamily, which includes one of the most diverse genera among Orchidaceae, Epidendrum. Based on data on phenology, floral morpho‐anatomy, pollinators, pollination mechanisms and breeding system, the reproductive biology of E. avicula was studied in south‐eastern Brazil. Epidendrum avicula possess osmophores that produce a citric fragrance at night. The flowers attract Tipulidae flies and several families of microlepidoptera that drink the nectar produced in a tube formed by the adnation of the labellum and column. As is common in Epidendrum, after removing the pollinarium, both crane flies and micro‐moths get trapped by the proboscis, which frightens the insects and inhibits any possible intent to immediately visit another flower. The behavior of the pollinators on flowers, plus the retention of the anther cap by the pollinarium, results in a reduction in the occurrence of geitonogamy. Because E. avicula is self‐incompatible, the consequence of pollinator behavior and the floral mechanisms tend to reduce the pollen loss. As far as we know, this is the first study to report the reproductive biology of a species of Epidendroideae pollinated by crane flies and microlepidoptera. Based on more recent concepts of plant–pollinator interactions, although E. avicula is pollinated by several species belonging to two distinct orders, suggesting an unspecialized pollination system is involved, nectar‐seeking microlepidoptera and Tipulidae flies can be recognized as a single functional group.     

Floral biology and mechanisms of spontaneous self‐pollination in five neotropical species of Gentianaceae

Cross‐ and self‐fertilization in angiosperms are regulated by several factors, and a knowledge of the mechanism and time of spontaneous self‐pollination offers opportunities for a better understanding of the evolution of mating systems and floral traits. The floral biology of five species of Gentianaceae found in high‐altitude neotropical grassland is presented, with emphasis on the mechanisms that promote spontaneous self‐pollination. A presumed floral Batesian mimicry system is suggested between the rare and rewardless Zygostigma australe and Calydorea campestris, a species of Iridaceae with pollen‐flowers, pollinated by syrphids and bees. The floral morphology of the other four gentian species points to three different pollination syndromes: melittophily, phalaenophily and ornithophily. However, with the exception of the nocturnal Helia oblongifolia, flowers are nectarless and appear to exhibit non‐model deceptive mechanisms, providing similar floral cues to some sympatric rewarding species with the same syndrome. The similar mechanism of spontaneous self‐pollination in Calolisianthus pedunculatus, Calolisianthus pendulus and H. oblongifolia (Helieae) is based on the stigmatic movements towards the anthers. Selfing is promoted by movements of the style/stigma and of the corolla in Deianira nervosa and Z. australe (Chironieae), respectively. The movements of stamens, style and stigma during anthesis seem to be the most common method of spontaneous self‐pollination in angiosperms. It is suggested that the evolution of delayed spontaneous self‐pollination would be more expected in those taxa with dichogamous flowers associated with herkogamy. Such a characteristic is frequent in long‐lived flowers of certain groups of Asteridae, which comprise most documented cases of autonomous selfing. Thus, the presence of dichogamy associated with herkogamy (which supposedly evolved as a result of selection to promote both separation of male and female functions and the efficient transfer of cross pollen) may be the first step in the adaptive evolution of delayed selfing to provide reproductive assurance. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 357–368.     

Reproductive ecology of the carnivorous plant Pinguicula moranensis (Lentibulariaceae)

• The interaction of plants with pollinators can be a determinant of their reproductive fitness. However, information about the pollination biology of carnivorous plants is scarce. To increase knowledge of reproductive ecology of carnivorous plants we focused on Pinguicula moranensis. Specifically, based on the presence of large, zygomorphic and spurred flowers, we predicted higher reproductive fitness in cross‐pollinated than in self‐pollinated flowers.
• Within a plot of 51 m² we characterised the reproductive phenology, including flower lifespan and stigmatic receptivity. We identified pollinators and their movement patterns within the plot. Breeding system was experimentally evaluated using hand‐pollination (i.e. autonomous, self‐ and cross‐pollination).
• Flowers of P. moranensis were visited by long‐tongued pollinators, mainly members of the Lepidoptera. Hand‐pollination experiments confirmed our prediction and suggest that flower traits might favour cross‐pollination.
• We mainly discuss the implications of the patchy distribution of plants and behaviour of pollinators on gene movement in this plant species, as pollination between genetically related individuals could be occurring.

     

Nectarless flowers with deep corolla tubes in Pedicularis: does long pistil length provide an arena for male competition?

Pollinator‐mediated selection does not seem to have a direct influence on the evolution of a long corolla tube in a nectarless flower. We hypothesized that the long pistil length of the nectarless flower with a deep corolla tube provided an opportunity for male competition. Pedicularis siphonantha, a nectarless and partially self‐incompatible lousewort with substantial variation in corolla tube length, was used to test the hypothesis. We tested whether and how corolla tube length affected seed production per capsule and seed germination rate with different pollination treatments. Flowers were hand‐pollinated with pollen from one self donor and one outcross donor and mixed pollen grains consisting of equal amounts from the two donor types, respectively. Additionally, seeds from open‐pollinated flowers with different corolla tube lengths were collected separately for measurement of germination rate. Pollination treatment and corolla tube length significantly affected number of seeds per capsule. Moreover, a significant positive relationship between seeds per capsule and corolla tube length was found when mixed hand pollination was conducted. Seeds of self hand‐pollinated flowers had a lower germination rate than those from outcross‐pollinated flowers. Under open pollination, seeds from flowers with longer corolla tubes tended to have higher germination rate. In P. siphonantha, outcross pollen may have a higher probability of contributing to the next generation when transferred to flowers with longer corolla tubes. The pistil length, therefore, should be seen as a female choice mechanism, which provides an arena for male‐to‐male competition. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 526–532.     

Floral biology of two Vanilloideae (Orchidaceae) primarily adapted to pollination by euglossine bees

Vanilloideae comprises 15 genera distributed worldwide, among which are Vanilla and Epistephium (tribe Vanilleae). Based on field and laboratory investigations, the pollination biology of V. dubia and E. sclerophyllum was analysed. The former was surveyed in a semi‐deciduous mesophytic forest at the biological reserve of Serra do Japi and in a marshy forest at the city of Pradópolis, southeastern Brazil. The latter was examined in rocky outcrop vegetation in the Chapada Diamantina, northeastern Brazil. In the studied populations, the tubular flowers of V. dubia and E. sclerophyllum were pollinated by bees. Pollen was deposited on either their scutellum (V. dubia) or scutum (E. sclerophyllum). The mentum region of V. dubia is dry, whereas that of E. sclerophyllum presents a small quantity of dilute nectar. Flowers of E. sclerophyllum are scentless, while those of V. dubia are odoriferous. Although V. dubia is self‐compatible, it needs a pollinator to produce fruit. In contrast, E. sclerophyllum sets fruit through spontaneous self‐pollination, but biotic pollination also occurs. Both species are primarily adapted to pollination by euglossine bees. Pollination by Euglossina seems to have occurred at least twice during the evolution of Vanilleae. Furthermore, shifts between rewarding and reward‐free flowers and between autogamous and allogamous species have been reported among vanillas.     

Are breeding system and florivory associated with the abundance of Tillandsia species (Bromeliaceae)?

Plant species abundance is partly determined by reproductive success and the factors that limit this success. We studied the flowering phenology, breeding systems and florivory in a community of seven epiphytic Tillandsia spp. in a tropical dry forest in central Mexico. Flowering periods were distributed throughout the year, and corolla sizes suggested that most species share pollinators. The most common breeding system was self‐incompatibility (Tillandsia achyrostachys, T. caput‐medusae and T. hubertiana), T. lydiae was infertile, T. circinnatioides was partially self‐compatible and T. recurvata and T. schiedeana were self‐compatible with high autonomous self‐pollination. Floral morphology suggests that delayed selfing occurs in the autonomous self‐pollinated species, and separation between stigma and stamens could result in self‐pollination in the remaining species being avoided. Less than 5% of the inflorescences in the most abundant species (T. recurvata) suffered damage by florivores, but > 40% of inflorescences were damaged in the other species. In damaged inflorescences, fruit set decreased by up to 89%. Our data show that the dominant species (T. recurvata) is autogamous and its reproductive success is slightly reduced by resource constraints and florivory. In the less abundant species, resource limitation and florivory dramatically reduced reproductive success, but the strength of these limiting factors is season dependent. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 50–65.     

Reproductive biology and pollination of Utricularia reniformis A.St.‐Hil. (Lentibulariaceae)

Utricularia reniformis is an endemic Brazilian carnivorous plant, most common in high‐altitude grasslands. Knowledge of the reproductive biology of U. reniformis is essential for planning conservation strategies, but it is currently poorly understood. Thus, we studied the floral morphology, floral biology, breeding system and pollination of this species. U. reniformis produces and stores nectar in the flower spur, a classic feature of bee‐pollinated flowers, and we recorded Xylocopa sp. and Bombus sp. as pollinators. Moreover, although it is self‐compatible it is an obligate animal‐pollinated species, as the sensitive stigma avoids self‐pollination. However, in natural conditions reproductive success is low due to the rarity of visits from pollinators. We suggest that the low reproductive success caused by a deficit of pollinators may affect gene flow, causing loss of genetic diversity in U. reniformis.     

Breeding systems in Clivia (Amaryllidaceae): late‐acting self‐incompatibility and its functional consequences

Late‐acting (ovarian) self‐incompatibility, characterized by minimal or zero seed production following self‐pollen tube growth to the ovules, is expected to show phylogenetic clustering, but can otherwise be difficult to distinguish from early‐acting inbreeding depression. In Amaryllidaceae, late‐acting self‐incompatibility has been proposed for Narcissus (Narcisseae) and Cyrtanthus (Cyrtantheae). Here, we investigate whether it occurs in the horticulturally important genus Clivia (Haemantheae) and test whether species in this genus experience ovule discounting in wild populations. Seed‐set results following controlled hand pollinations revealed that Clivia miniata and C. gardenii are largely self‐sterile. Self‐ and cross‐pollinated flowers of both species had similar proportions of pollen tubes entering the ovary, and those of C. gardenii also did not differ in the proportions of pollen tubes that penetrated ovules, thus ruling out classical gametophytic self‐incompatibility acting in the style, but not early inbreeding depression. Flowers that received equal mixtures of self‐ and cross‐pollen set fewer seeds than those that received cross‐pollen only, but it was unclear whether this effect was a result of ovule discounting or interactions on the stigma. The prevention of self‐pollination by the emasculation of either single flowers or whole inflorescences in wild populations did not affect seed set, suggesting that ovule discounting is not a major natural limitation on seed production. Flowers typically produce one to three large fleshy seeds from approximately 16 available ovules, even when supplementally hand pollinated, suggesting that fecundity is mostly resource limited. The results of this study suggest that Clivia spp. are largely self‐sterile as a result of either a late‐acting self‐incompatibility system or severe early inbreeding depression, but ovule discounting caused by self‐pollination is not a major constraint on fecundity. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 155–168.     

Reproductive biology of the Red List species Polemonium caeruleum (Polemoniaceae)

The majority of flowering plants, including many rare and threatened species, are pollinated by animals, but little is known of pollination and breeding systems of many endangered species. Polemonium caeruleum (Polemoniaceae) is a red‐listed species and is regarded as dichogamous, self‐compatible and bee pollinated. However, some studies show that it is visited by a vast assemblage of anthophilous insects from many taxonomic orders and that breeding systems vary greatly between closely related taxa of this genus. Over a period of 3 years we investigated breeding system, dichogamy, nectar secretion and composition, insect visitations and pollen loads in flowers of P. caeruleum in north‐eastern Poland to determine whether the reproductive biology of the plant explains its rarity. Contrary to published data, our study plants were self‐incompatible and showed a high degree of outcrossing. Our experimental work confirmed the occurrence of protandry in this species, revealed that nectar is sucrose‐dominant and proline‐rich and, for the first time for Polemoniaceae, that nectar secretion and nectar sugar concentration in flowers of P. caeruleum is female‐biased. Although flowers were visited by at least 39 species of insects from five taxonomic orders, overall the plant exhibited many characters associated with bee pollination, and analysis of insect performance showed that bumblebees and honeybees are the key pollinators; occasionally hoverflies and butterflies may also be involved. We conclude that, in terms of pollination system, P. caeruleum demonstrates high apparent generalization, but low realized generalization, and is a functional specialist, as most pollinators belong to a single functional group (guild). Its conservation status, at least in our study population, cannot be explained in terms of the biological properties of its breeding or pollination systems; rather, the present decline of the species is caused by habitat loss. However, if this process and bumblebee decline in Europe continue, P. caeruleum populations may diminish in numbers and density and, owing to the self‐incompatibility of the species, quickly become severely pollen‐limited, thereby accelerating further local extinctions. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 92–107.     

Pollination ecology of the pre-Pyrenean endemic Petrocoptis montsicciana (Caryophyllaceae): effects of population size

Petrocoptis montsicciana (Caryophyllaceae) is a threatened pre‐Pyrenean endemic that grows exclusively on caves and walls of limestone. We studied its pollination ecology by monitoring phenology and by evaluating pollen and nectar production, pollinator activity (frequency and behaviour of visitors), quantity and quality of pollination services, pollen/ovule ratio, and seed set in response to insect exclusion and self‐compatibility tests. We also analysed the effect of population size on reproductive mechanisms by comparing a large and a small population. Flowers of P. montsicciana produced nectar and were visited by Hymenoptera (79.7%), Diptera (11.5%), and Lepidoptera (8.8%). The most frequent pollinators (60.6% of total visits) were long‐tongued bees of the genus Anthophora. Both populations had a similar range of pollinators. We found a correlation between the number of visited flowers and the number of open flowers per census; 88.7% of pollen grains deposited on the stigmas were conspecific and the main competitor was another chasmophyte plant, Antirrhinum molle. Bagged flowers set seeds but significantly less so than hand‐self‐pollinated and control flowers. Thus, although self‐compatible and self‐pollinated, entomophilous pollination of P. montsicciana is required in order to explain c. 10–40% of total seed set, in accordance with P/O ratio estimations. Bagged flowers from the small population set significantly more seeds than the large one. Visitation rates were lower in the small population, but, unexpectedly, showed higher stigmatic pollen loads and similar or higher seed set. These results suggest an increase of spontaneous selfing rates in the small population, probably favoured by a smaller flower size, which can not only assure reproductive success when pollinators are scarce, but also provide additional potential to adapt to climatic changes. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 76 , 79–90.