Analysis Of Pollen Loads Research Articles

Pollen inventory in urban remnants of Cerrado in midwest Brazil

Studies focusing on plant-pollinator interactions in urban environments aim to understand how the anthropized landscape affects interactions and, consequently, the reproductive success of plants. In these studies, the identification of plant species visited can be performed through focal observations and the analysis of pollen loads carried by vectors. Therefore, pollen inventories are essential for assisting in studies focused on the analysis of pollen grains carried by pollinators and palynological studies, favoring the scientific interpretation of the biodiversity in each area. Data was collected over 12 months in 14 remnants of different physiognomies of the Cerrado domain within the urban perimeter of Campo Grande, Mato Grosso do Sul. In these places, the 118 plant species distributed in 39 families that received visits from pollinating insects had their pollen grains photographed and characterized. The families with the highest number of species were Asteraceae, with 19 species (22.42%); Fabaceae, with 15 species (17.7%), and Malvaceae, with nine species (10.62%). The high representation of Asteraceae can be explained as its being the largest botanical family among Angiosperms, being adapted to various types of environments, and being very common in anthropized areas. This pollen guide can support future studies focused on plant-pollinator interactions, mostly in urban remnants of the Cerrado.

A shift between bee and wasp pollinators explains floral divergence in the Duvernoia clade of Justicia (Acanthaceae)

Abstract Floral divergence among sister taxa can arise from pollinator shifts and play a role in speciation. We investigate a potential case of pollinator-driven divergence in the Duvernoia clade of Justicia (Acanthaceae), which includes two species with markedly divergent floral morphology. Pollinator observations and pollen load analyses showed that Justicia aconitiflora is pollinated by vespid wasps, while its sister taxon Justicia adhatodoides is confirmed to be pollinated exclusively by large carpenter bees. Reciprocal nectar-feeding experiments show that wasps and bees are not deterred by the taste of nectar of non-preferred species. Floral morphology matches body and tongue morphology of these two insect groups, and this phenotypic matching mediates pollen transfer and physical access to nectar. Controlled pollination experiments showed that both species are self-compatible, yet dependent on pollinator visits for fruit-set. Historical reconstruction of pollination system evolution in Justicia indicates that the direction of the shift in the Duvernoia clade was from bee to wasp pollinators. This study provides a compelling example of a transition between bee and wasp pollination, and highlights the effects of floral architecture on specialization in plant pollination systems.

Assessing important floral resources supporting two species of Exomalopsis (Apidae) in agricultural cultivation areas: insights from pollen load analysis

Assessing important floral resources supporting two species of Exomalopsis (Apidae) in agricultural cultivation areas: insights from pollen load analysis

Diurnal versus nocturnal pollination in a subalpine wetland: From network structure to plant reproduction

Diurnal and nocturnal pollinators are fundamental for the functioning of natural ecosystems and food security. However, differences between diurnal and nocturnal pollination networks and the contribution of these pollinators to plant fecundity have not been assessed comprehensively within a community context. In the Dajiuhu subalpine wetland of central China, we supplemented data from an intensive field survey with the analysis of pollen loads carried by diurnal and nocturnal pollinators to compare the structures of diurnal and nocturnal pollination networks using network parameters. Simultaneously, we compared the contribution of diurnal and nocturnal pollinators to plant reproduction of the nine dominant species based on stigma pollen placement. We found that although diurnal and nocturnal pollination networks exhibited a similar structural organisation, the diurnal network displayed greater stability and broader interaction with pollinators and plants compared to the nocturnal network. However, nocturnal pollinator species tended to establish less generalised interactions with the available floral resources. Both diurnal and nocturnal pollinators played a significant role in plant reproduction, and nocturnal pollination can result in greater pollen germination. In terms of stability, the lower redundancy of links within nocturnal networks suggests they may be more vulnerable to the temporary or permanent disappearance of plant resources in the study area. Our findings highlight the differences in the contributions of diurnal and nocturnal pollinators to plant reproduction at the community level, demonstrating that nocturnal pollinators are not redundant in maintaining species diversity in communities. This knowledge should play a pivotal role in preventing future pollination declines and improving pollinator conservation efforts.

Pollen sources of Asian honeybee (Apis cerana Fabricius) in Paschim Medinipur district of West Bengal, India

The Asian honeybee (Apis cerana) occurs across the south, southeast and east Asia. The species is utilised in apicultural practices. But the available documents about their floral resources, especially pollen sources, are limited. However, it is a mandatory requirement in a sustainable honeybee management programme. In the present study, we conducted palynological analyses of pollen loads and field surveys to determine pollen sources for the honeybees in West Bengal, India. The honeybee species is regarded as a generalist forager with significant floral constancy supported by homogenous pollen loads with diverse pollen types (here 58). Important pollen-contributed plants were Acacia auriculiformis, Brassica juncea, Cocos nucifera, Eucalyptus sp., Neolamarckia cadamba, Peltophorum pterocarpum, Sesamum indicum and Tridax procumbens. In the semi-urban area of Midnapore town, honeybees mainly depend on planted trees and weeds for pollen sources. While in rural agricultural belts, they also visited wild trees and several cultivated crops. The bee-visited plants are diverse types regarding plant habits, flowering phenology and floral characteristics. These data will be helpful in the management of Asian honeybees, providing pollination services to cultivated crops and thereby enhancing crop yield.

Environmental variables and species traits as drivers of wild bee pollination in intensive agroecosystems—A metabarcoding approach

AbstractWild bees are known to be efficient pollinators of wild plants and cultivated crops and they are essential ecosystem service providers. However, wild bee populations have been suffering from significant declines in the last decades mainly due to the use of agrochemicals. Within this framework, we aimed to characterize wild bees' pollination spectrum (i.e., the community of pollinated flowering plants) in intensive agroecosystems, and describe the environmental variables and wild bee species traits influencing the pollination. To do this, we conducted metabarcoding analyses of pollen loads from wild bees collected in sunflower crops in the French region of Nouvelle‐Aquitaine. Our study revealed that wild bees visited flowering plants corresponding to 231 different operational taxonomic units, classified into 38 families of which Asteraceae, Brassicaceae, and Apiaceae were the most visited and more than 90% of the visited taxa turned out to be wildflowers. We also analyzed the potential effect of environmental variables and wild bee species traits in governing their choice of pollinated plants. The community composition of pollinated plants varied depending on the flowering stages of the sunflower and the farming system. Our results also show that pollination niche breadth (alpha diversity) varied depending on the flowering stages of the sunflower but was not different between organic and conventional farming systems. Regarding wild bee species traits, the community composition of pollinated plants varied in relation to wild bees' body sizes and sociality levels. Our results are consistent with previous studies, suggesting that solitary bees are more specialist when it comes to flower selection than social bees, which are more generalist. The metabarcoding of pollen loads enabled us to draw a global picture of plant–wild bee interactions in an intensive agroecosystem. Our findings support the hypothesis that a higher diversity of weeds may increase wild bee diversity in intensive agroecosystems.

Composition and Nutrition of Wild Bees in Solanum melongena L. Agroecosystems in Pune, Maharashtra, India

Eggplant, (Solanum melongena L.), also called aubergine or Guinea squash, in the nightshade family (Solanaceae) is an economically important crop in India. We investigated the significance of Solanum melongena pollen in the diet of wild bees found in agroecosystems by examining pollen on the bees using a pollen load analysis and a nutritive analysis. We selected five agricultural sites that cultivate S. melongena near Pune, Maharashtra, India. At each site, over a two-year period, we sampled the wild bees that visited mature flowers. We sampled pollen from mature flowers and also from the bodies of the bee specimens. The pollen grains from the bees were observed under a light microscope and a scanning electron microscope. They were counted using a Neubauer chamber and the pollen probability index for each bee species was calculated. The nutritive value of S. melongena pollen was estimated by extracting and characterising their proteins using liquid chromatography mass-spectrometry. Protein peptides sequences were extracted from the NCBI protein database to examine their essential amino acids. We collected 324 bees representing 11 species in three families involved in S. melongena pollination. Apis florea and A. cerana were the most abundant bees that visited S. melongena flowers. Pollen load size is highly variable ranging between few thousand to 134146 pollen grains per bee. However, the pollen probability index indicated a high degree of specificity to S. melongena pollen. S. melongena has high pollen protein content and a total of 10 different proteins were identified that are important for plant cell activities as well as the nourishment of pollinators. Further proteomic characterization of the indicated that nearly half the essential amino acids played and nutrient role in the bees. This study highlights that nutrititive composition of S. melongena pollen and highlights its potential to play a significant role in wild bee diets.

Relative importance of two bat species as pollinators of Neobuxbaumia tetetzo (Cactaceae): Evidences from morphometric and pollen load analyses

AbstractNeobuxbaumia tetetzo is a columnar cactus whose flowers are visited by the bat species Choeronycteris mexicana and Leptonycteris yerbabuenae. Although both bat species are considered the pollinators of N. tetetzo, the probability of pollination of each bat species has not been estimated. In this study, we determine the relative importance of C. mexicana and L. yerbabuenae as pollinators of N. tetetzo. The probability of pollination was estimated using two different approaches: (i) morphological correspondence between head (linear traits [total head length, snout length, and face height and width]) and cranial traits (shape traits) of bats and flower traits (linear [internal floral tube length including and excluding the nectary, corolla diameter, stamen length, style length, and corolla tube diameter] and shape traits), and (ii) pollen load analyses to estimate the percentage of occurrence (PO) and the pollination probability index (PPI). Our results showed a lack of a significant correspondence between both head and cranial traits of C. mexicana and the flowers of N. tetetzo, and linear morphological correspondence between total head length of L. yerbabuenae and flower length. Pollen loads of C. mexicana were composed by seven different pollen types, its PO and PPI were 41.87 ± 9.53% and 0.29, respectively. Leptonycteris yerbabuenae pollen loads were composed by three pollen types, with a PO of 78.29 ± 13.67% and a PPI of 0.67. Our results suggest that whereas C. mexicana has a low constancy to the flowers of N. tetetzo, L. yerbabuenae has a higher probability of pollination.

Palaearctic Osmia bees of the subgenera Allosmia and Neosmia (Megachilidae, Osmiini): biology, taxonomy and key to species

Osmia (Allosmia) and O. (Neosmia) are two closely related Palaearctic osmiine bee subgenera (Megachilidae, Megachilinae, Osmiini) comprising eleven and ten species, respectively. Analysis of female pollen loads revealed that the representatives of O. (Allosmia) and O. (Neosmia) are pollen generalists collecting pollen on up to 13 and 17 plant families, respectively. The species of both subgenera exclusively nest in empty snail shells and use chewed leaves as main nest building material, often in combination with fragments of mollusc shells and densely packed small particles, such as small stones, earth crumbs or plant fibers, which are used to barricade the nests. The taxonomic revision of the two subgenera revealed the existence of two undescribed species, O. (Allosmia) gemina spec. nov. from the southern Levant and O. (Neosmia) nigrocalcaribus spec. nov. from the Maghreb. Osmia fossoria Pérez, 1890 syn. nov. and O. decorata Morawitz, 1886 syn. nov. are newly synonymized with O. (Allosmia) lhotelleriei Pérez, 1887 and O. (Allosmia) melanura Morawitz, 1871, respectively, whereas the former synonymization of O. (Neosmia) rosea Friese, 1920 with O. scutispina Gribodo, 1894 is rejected. Osmia (Neosmia) purpurata Ducke, 1899 is regarded as a nomen dubium. Osmia (Allosmia) soror Pérez, 1896 and O. (Neosmia) secunda Peters, 1977 are treated as species rather than as subspecies of O. rufohirta Latreille, 1811 and O. tingitana Benoist, 1969, respectively, due to clear morphological gaps and partly sympatric occurrence. Identification keys for all species of the two subgenera are given.

Methods Employed in the Determining Nectar and Pollen Sources for Bees: A Review of the Global Scenario

Abstract Flowering plants and pollinators are in a mutualistic association, where pollinators collect floral resources and plants receive pollination services. Bees and other pollinators are declining in many parts of the world, and their loss affects the functional composition of fauna, flora, and habitats. Different strategies are being deployed to improve pollinator services, including the management of bees. Sustainable management of a bee species strongly depends on floral resource availability. Therefore, beekeepers need to have adequate knowledge about the surrounding vegetation (especially nectar and pollen sources for the bee species). Diverse methodologies are used around the world to determine floral resources for bees. Field surveys and pollen analysis of honey, corbicular/scopal pollen loads, residual pollens in brood cells, forager’s body surface pollen content, and internal organs (gut, intestine, crop, etc.) were used by the researchers. For pollen identification, most researchers carried out microscopy-based methods. However, pollen DNA-based methods were also used by researchers in recent years. Regarding the morphology-based identification, most researchers processed pollen samples according to Erdtman’s acetolysis method to increase the visibility of diagnostic characteristics of the pollen grains. The method specified by the International Commission for Bee Botany was used to conduct qualitative and quantitative pollen analysis on honey samples. For quantitative pollen load analysis, researchers used numerous techniques that may have been the most effective. Our discussion about the different techniques utilized to determine floral resources of a bee species will be helpful for researchers in selecting a suitable protocol and may assist in developing superior methodologies.

Papilio butterfly vs. hawkmoth pollination explains floral syndrome dichotomy in a clade of Lilium

Abstract Pollination niche shifts can drive remarkable floral divergence between closely related plant species. The Leucolirion clade of Lilium contains species with either tepal-recurved or trumpet-shaped flowers. The tepal-recurved flowers are bright orange and might be pollinated by butterflies and/or birds. The trumpet-shaped flowers are mostly pale and strongly fragrant and might permit visitation by a variety of hawkmoths. Lilium leucanthum has trumpet-shaped flowers, and some populations of this species show dark coloration on the floral outer surface, suggesting pollination by mammals. We identified pollinators and examined the dependence of reproduction on pollinators by floral visitor observations, pollen load analysis and pollination experiments. We also analysed floral traits to contrast the two floral syndromes involving different lepidopteran groups. The tepal-recurved lilies are specialized on a group of Papilio butterflies for pollination with pollen predominantly attached to the hindwings. The trumpet-shaped flowers are almost exclusively pollinated by hawkmoths, including diverse species with proboscises of different lengths. No mammal visitation was found to the populations of L. leucanthum with dark outer surfaces of flowers. Self-incompatibility prevails throughout the clade, including the populations in which pollinators were scarce. The butterfly- and hawkmoth-pollinated species display contrasting floral syndromes. Our findings confirmed that the dichotomy in floral syndrome in the Leucolirion clade is associated with Papilio butterfly vs. hawkmoth pollination, whereas intraspecific variation in colour of the floral outer surface of L. leucanthum many need a non-pollinator explanation.

Are floral traits good predictors of effective pollinators? A test of pollination syndromes

AbstractPollination syndromes have been widely used to predict the groups of pollinators of plants. Their predictability has been demonstrated for plant species pollinated by bees, birds, and bats. However, the importance of other aspects on the predictability of pollination syndromes still remain unknown. For instance, plant life cycle has not been considered in evaluations of the pollination syndrome predictability. The goal of this study was to evaluate the predictability of pollination syndromes in nine species with contrasting life cycles. Pollination syndromes were inferred based on floral traits of each plant species, whereas pollinator effectiveness of each group of floral visitors was established through pollen load analysis. Predictability of pollination syndromes was tested through the association between floral traits and the abundance of the most‐effective pollinators. Bees, flies, birds, beetles, and butterflies were the primary and secondary pollinators inferred from floral traits of each species. Although six out of the nine plant species studied were visited by effective pollinators; only four species were effectively pollinated by the groups of primary or secondary pollinators predicted from floral traits. However,Dahlia coccineaandTigridia pavoniawere the only species in which the predicted pollinator group was both effective and showed an association with floral traits. Pollination syndromes were not predictive of pollinators for any of the annual and perennial plant species. Although pollination syndromes are useful to understand some aspects of the reproductive biology of plant species, several other factors might have a role on their predictability.

Pollination efficiency and pollen limitation in bistaminate vs tetrastaminate Lamiaceae

AbstractThe evolution of bilabiate flowers in Lamiaceae has several times led to a reduction in stamen number. It is generally assumed that stamen reduction goes along with decreasing pollen production. One should, therefore, expect that bistaminate flowers have either a more efficient pollen transfer mechanism or a higher selfíng rate than tetrastaminate species to adapt to the stamen reduction. We tested this hypothesis in a community of Lamiaceae including three bistaminate and three tetrastaminate species. The results of selfing experiments, extra‐pollination, counting pollen number, and stigmatic pollen load analysis were used to calculate the autonomous selfing index, the pollen limitation index, and the pollination efficiency index. The results indicate a significantly lower pollen number in bistaminate flowers than in tetrastaminate flowers of similar anther size. Bistaminate species shared a higher selfing rate which was related to their structural adaptation to delayed selfing. In Ziziphora clinopodioides, the delayed selfing was accompanied by low pollination efficiency, and plants suffered from pollen limitation at the location studied. However, in Salvia sclarea and Salvia hypoleuca, which benefited from a relatively high pollination efficiency, no pollen limitation was observed. Our results reveal a close association between adaptive mechanisms such as increasing precision of pollen transfer and evolution of delayed selfing with stamen reduction in bistaminate Lamiaceae.

Novel pollen analogue technique shows bumblebees display low floral constancy and prefer sites with high floral diversity

ContextThere have been dramatic global declines in pollinating insects. A common land management intervention to support wild pollinators is to plant non-crop flowering plants (‘pollinator planting’). However, there are limited data on which species or spatial arrangement of planting provide maximum benefit to wild pollinators.ObjectivesHere we investigate which flowering species and locations are visited by free-foraging Bombus terrestris (buff-tailed bumblebees) in species-rich semi-natural grassland and woodland.MethodsTwo study nests of buff-tailed bumblebees were established in Wytham Woods, UK. Pollen analogue pigments were sprayed on open flowers in the study area over a period of two months, with unique colours used to identify separate sections of the study area. Pollen load analysis was used to identify forage species and foraging locations.ResultsBumblebees showed low flower constancy, visiting five flower species per trip on average, and as a group the sampled bumblebees visited 36 of the 49 plant species identified in study area surveys. Many individuals foraged in multiple, spatially-discrete locations during single trips.ConclusionsThe positive relationship between floral diversity and pollen load species diversity, and the positive relationship between site floral diversity and frequency of visitation, suggest behavioural strategies that maximize the diversity of flower species visited, in line with the energetic costs and benefits hypothesis. This supports recommendations for pollinator plantings with high species diversity, potentially spread across many small forage areas across the landscape.

Moths pollinate four crops of Cucurbitaceae in Asia

AbstractPollination ecology of many crops is not fully known, especially in tropical and subtropical regions. Non‐bee pollinators may contribute substantially to crop yield, even if they do not receive much attention. Although moth pollination has fascinated ecologists and evolutionary biologists since Darwin, crop pollination by moths has not been well investigated and experimentally examined. Hence, we explored the pollination ecology of four cucurbit crops with crepuscular or nocturnal flowers. Lagenaria siceraria (Molina) Standl., Luffa acutangula (L.) Roxb., Trichosanthes anguina L., and Trichosanthes kirilowii Maxim. all display floral traits suggestive of moth pollination, such as opening around dusk or in evenings and secreting ample dilute nectar. We demonstrated that these crops’ flowers attracted a wide range of moth species, especially hawkmoths. The assemblage of flower‐visiting moths varied according to location and season. Pollination treatments and pollen load analysis confirmed the pollination of the four crops by moths, especially hawkmoths. Our results provide evidence for the value as wild pollinators for the four crops, for which domesticated bees cannot provide reliable pollination services in practice. This study lends support to the proposal to pay more attention to the value of non‐bee pollinators and to leave some areas unexploited in rural landscapes for the conservation of wild pollinators, including moths.

Pollination effectiveness of European honeybee, Apis mellifera (Hymenoptera: Apidae), in an Oriental persimmon, Diospyros kaki (Ericales: Ebenaceae), orchard

Most common cultivars of Oriental (or Japanese) persimmon, Diospyros kaki Thunb. (Ericales: Ebenaceae), set mostly female flowers and require pollen from male flowers of other cultivars for pollination. Growers often introduce the European honeybee, Apis mellifera L. (Hymenoptera: Apidae), into their orchards to promote pollination. Here, we investigated the pollination effectiveness of A. mellifera for D. kaki ‘Saijo,’ by monitoring flower visitors, analyzing pollen grains on bees’ body surfaces, and comparing the number of mature seeds in fruits among years with different pollinator availabilities. Apis mellifera and the bumblebee Bombus ardens ardens Smith (Hymenoptera: Apidae) were the major visitors for 3 years, although their dominance varied among years. The number of mature seeds was positively correlated with the number of B. ardens ​ardens visiting D. kaki flowers, but not with that of A. mellifera. Apis mellifera might be less efficient because visitors to female flowers carried significantly fewer pollen grains on their body surfaces than those of B. ardens ​ardens. Analysis of pollen loads of honeybees captured at their nest entrance suggested their preference for red clover, Trifolium pratense L. (Fabales: Fabaceae), and Toxicodendron spp. (Sapindales: Anacardiaceae), over D. kaki as a pollen source in our study site. The effectiveness of A. mellifera on D. kaki pollination should be carefully evaluated considering the effects of coexisting floral and pollinator species.

Pollen Loads of Flower Visitors to Açaí Palm (Euterpe oleracea) and Implications for Management of Pollination Services.

Understanding the functional roles of different pollinator species is crucial to the development of sustainable farming practices in pollinator-dependent crops. However, this can be challenging for crop plants in tropical regions with hyper-diverse pollinator communities. Here, we assess pollen loads of different insect visitors to inflorescences of açaí palm (Euterpe oleracea), the most important native crop in the Amazon estuary region. Flower-visiting insects were collected from pistillate (female) inflorescences at eight sites, including four managed floodplain forests and four plantations. Pollinator Importance Value Index (PIVI) and Relative Importance (RI) scores were calculated for common visitor taxa (≥ 10 individuals) using sum visit frequencies and median pollen loads. Pollen load analyses revealed that over seventy insect taxa, including bees, flies, beetles, wasps and ants, were effective vectors of E. oleracea pollen. Native bees, including both solitary and eusocial taxa, were the most efficient pollen vectors, with median pollen loads at least eight times higher than those of the next best insect group (flies). Insect pollen loads were at their highest between 0800 and 1300 hours, and four insect taxa had RI scores > 0.05, including two meliponine bees belonging to the Trigona genus (Trigona branneri Cockerell and Trigona pallens Fabricius) and two halictid bee genera (Augochloropsis and Dialictus). Our results suggest that native bees play an important role in açaí pollination and should be the primary focus of pollinator management in açaí production systems.

Palaearctic Osmia bees of the subgenera Hemiosmia, Tergosmia and Erythrosmia (Megachilidae, Osmiini): biology, taxonomy and key to species

Osmia (Hemiosmia), O. (Tergosmia) and O. (Erythrosmia) are three related Palaearctic osmiine bee subgenera (Megachilidae, Megachilinae, Osmiini) comprising eight, seven and four species, respectively. Analysis of female pollen loads and field observations revealed that the species of both O. (Hemiosmia) and O. (Tergosmia) have a distinct or even exclusive preference for Fabaceae as pollen hosts. Species of O. (Erythrosmia) also collect pollen on Fabaceae, but additionally frequently visit nototribic flowers of Lamiaceae and Antirrhineae (Plantaginaceae), which they exploit by rubbing a specialized facial pilosity over the raised anthers. The representatives of O. (Hemiosmia) and the basal members of O. (Tergosmia) build their brood cells in self-excavated burrows in the ground, whereas the more derived O. (Tergosmia) species as well as the O. (Erythrosmia) species place them in preexisting cavities above-ground, which are empty snail shells hidden under prominences of rocks or under stones in the latter subgenus. In O. (Hemiosmia) and O. (Tergosmia), the brood cells are entirely constructed from foreign material and either consist of chewed leaves ("leaf pulp") in the former subgenus or are distinctly three-layered with a thin layer of mud sandwiched between two layers of large pieces of petals in the latter subgenus. In O. (Erythrosmia), the brood cells within the shell whorls are delimited by one-layered partitions of leaf pulp and the nests are closed by a barricade of densely packed small particles followed by a double wall of leaf pulp at the shell opening. The taxonomic revision of the three subgenera revealed the existence of an undescribed species, O. (Hemiosmia) spinicoxa spec. nov., which occurs in southwestern Morocco. The subgenus O. (Ozbekosmia) Zanden, 1994 syn. nov. is newly put into synonymy with O. (Tergosmia) Warncke, 1988. Osmia (Tergosmia) rhodoensis arquata Warncke, 1988 syn. nov. and O. (Tergosmia) tergestensis ononidis Ferton, 1897 syn. nov. are no longer accepted as valid subspecies of O. (Tergosmia) rhodoensis (Zanden, 1983) and O. (Tergosmia) tergestensis Ducke, 1897, respectively. Identification keys for all species of the three subgenera are given.

Specialisation in pollen collection, pollination interactions and phenotypic variation of the oil-collecting bee Chalepogenus cocuccii

Bee pollen gathering from a few related plant species is a specialisation known as oligolecty. Although it is an extended phenomenon, it has been scarcely explored in oil-collecting bees. At the geographic level, there is little information about oligolecty persistence and also about phenotypic variation of bees related with abiotic factors. We studied the pollen collection specialisation of the oil-collecting bee Chalepogenus cocuccii, its pollination interactions and phenotypic variation across its distribution range, by analyses of pollen loads, field observations and morphometric measurements. Observations and pollen analyses showed that across its distribution range, C. cocuccii preferred Nierembergia flowers not only for oil but also for pollen. We found two bee-morphotypes, though phenotypic variation was not related to abiotic variables. We postulate that C. cocuccii is a narrowly oligolectic species, phenotypically and ecologically specialised in Nierembergia.

Flower orientation in Gloriosa superba (Colchicaceae) promotes cross-pollination via butterfly wings.

Complex modifications of angiosperm flowers often function for precise pollen placement on pollinators and to promote cross-pollination. We explore the functional significance of the unusually elaborate morphology of Gloriosa superba flowers, which are divided into one hermaphrodite meranthium and five male meranthia (functional pollination units of a single flower). We used controlled pollination experiments, floral measurements, pollen load analyses and visitor observations in four populations of G. superba in South Africa to determine the breeding system, mechanism of pollination and role of flower in the promotion of cross-pollination. We established that G. superba is self-compatible, but reliant on pollinators for seed production. Butterflies, in particular the pierid Eronia cleodora, were the primary pollinators (>90 % of visitors). Butterflies brush against the anthers and stigma during nectar feeding and pollen is carried on their ventral wing surfaces. Butterfly scales were positively correlated with the number of pollen grains on stigmas. We demonstrate that the styles were orientated towards clearings in the vegetation and we confirm that the highest proportion of initial visits was to hermaphrodite meranthia pointing towards clearings. The flower morphology of G. superba results in effective pollen transfer on the wings of butterfly visitors. The style-bearing hermaphrodite meranthium of the flowers orientates towards open spaces in the vegetation, thus increasing the probability that butterflies land first on the hermaphrodite meranthium. This novel aspect of flower orientation is interpreted as a mechanism that promotes cross-pollination.