Convergence of anti-bee pollination mechanisms in the Neotropical plant genus <Emphasis Type="Italic">Drymonia</Emphasis> (Gesneriaceae)

The neotropical plant genus Drymonia displays a remarkable variety of floral shapes and colors. One feature that is particularly important to coevolution with pollinators involves the variable shapes and widths of corolla tubes. To evaluate the evolutionary context for changes in corolla shape, we constructed a phylogeny of 50 of the 75 species of Drymonia using molecular markers from plastid (trnK-matK) and nuclear regions (ITS and ETS). Mapping tube shapes on the phylogeny supports open, bell-shaped (campanulate) corolla shape as the ancestral character state for Drymonia, with multiple independent origins of constriction in the corolla tube. Corollas with constrictions take one of three tube shapes: a constricted flower opening and throat with a large, expanded pouch on the lower surface (hypocyrtoid); a constricted flower opening and throat lacking an expanded pouch on the lower surface (urceolate); or a constricted opening and throat where the sides of the corolla appear laterally compressed. Fieldwork demonstrates euglossine bees (mostly Euglossa spp. and Epicharis spp.) visit campanulate corollas while hummingbirds visit corollas that are constricted. Results support eight independent origins of constricted corolla tubes from ancestors with campanulate corolla tubes: 3 hypocyrtoid clades, 3 laterally compressed clades, and 3 urceolate clades (one of which represents a shift from a hypocyrtoid ancestor). Constricted corollas are associated with shifts from the ancestral condition of poricidal anther dehiscence, which presents pollen to pollinators in multiple small doses, to the derived condition of longitudinal anther dehiscence, which presents all pollen to pollinators simultaneously. The association of hummingbird pollination with constricted corolla tubes suggests that narrowing evolved as a barrier mechanism that prohibits the visitation of flowers by bees.     

Differential gender selection on flower size in two Neotropical savanna congeneric species

Larger flowers greatly increase among-individual pollen exchange within populations. However, water costs associated to transpirational cooling also increase with increasing flower size. Overall, the interplay between pollen and resource limitation determines the intensity of selection on flower size and this process is mostly dependent on gender and ecological context. To examine how pollinators and water use affect flower size, we determined corolla transpiration, pollen limitation, and selection through male and female fitness in two Kielmeyera species from the Brazilian cerrado flowering at different seasons. Hand-pollination experiments suggested pollen limitation through female fitness in both species, but K. coriacea showed lower limitation levels than K. regalis. For male fitness, the percentage of pollen removal was 1.5-times higher in K. coriacea. Higher air temperature and water deficit during flowering season of K. coriacea resulted in 4-fold higher corolla transpiration rates compared to K. regalis. Selection on flower size through male function was positive and significantly higher than selection through female components in both species. We also detected stabilizing selection in K. coriacea and positive selection in K. regalis on flower size through seed number. Our results suggest that selection on flower size in K. coriacea was mainly limited by water, whereas in K. regalis it was more limited by pollen. We demonstrate that differences in pollen and abiotic resource limitation determine gender-specific selection on flower size.     

Facilitative interactions among co-flowering <Emphasis Type="Italic">Primula</Emphasis> species mediated by pollinator sharing

We investigated flowering phenology, pollinator visitation and visitor community composition in communities of self-incompatible sympatric Primula species in a high-elevation Himalayan ecosystem. Within the tight constraints imposed by short growing seasons in such ecosystems, interactions among co-occurring plants for pollinators may vary from competition to facilitation, depending on the specifics of the system. We found that pollinator community composition changed with elevation in this system: lepidopterans were the dominant visitors at lower elevations (2200–3000 masl), bees (other than bumblebees) dominated at mid-elevations (3000–3800 masl) and bumblebees dominated at higher elevations (3800–4600 masl). However, within an elevation zone, there were no significant differences in pollinators amongst co-occurring Primula species. At a focal study site where multiple Primula species co-occurred, our results showed that even while the overall flowering periods of these species broadly overlapped, the peak flowering periods of different Primula species were temporally segregated. Upon further inferring the nature of interaction amongst co-flowering Primula species, we found that plots with higher Primula diversity (≥?2 species) and density (80–100 individuals) experienced significantly higher pollinator visitation, compared with plots with single species and low flower densities (40–50 individuals). Our results suggest that in this community of sympatric, self-incompatible Primula species, a broadly aggregated, synchronous floral display of multiple species results in pollinator facilitation by attracting a greater number of pollinator visitors. Within this broadly synchronous display, the temporal segregation of peak flowering period of individual species may reduce competition for pollinators and limit heterospecific pollen transfer.     

Effects of alien invasion by <Emphasis Type="Italic">Bombus terrestris</Emphasis> L. (Apidae) on the visitation patterns of native bumblebees in coastal plants in northern Japan

When alien pollinator species enter a native community of pollinators in which resource partitioning has been established, the pollination network between plants and pollinators may be modified through the interactions between the pollinators over the use of floral resources. We observed the floral-use patterns of native (Bombus hypocrita and B. deuteronymus) and alien (B. terrestris) bumblebee species in a coastal grassland in northern Japan. We analyzed the factors determining resource partitioning patterns. B. hypocrita tended to visit flowers with shallow or wide open corollas, such as Rosa rugosa, whereas B. deuteronymus visited flowers with complex or deeper corollas, such as Lathyrus japonicus. Given the wider floral preference of B. terrestris, floral use by the alien bumblebees consistently overlapped with that of native bumblebees. The visitation of B. terrestris to R. rugosa flowers was positively correlated with that of B. hypocrita. These bumblebee species frequently used similar floral resources, in part because of the large overlap in the seasonality of their foraging activity. The visitation frequency of B. deuteronymus to L. japonicus flowers was independent of the visitation frequency of other bumblebee species. The major visitation periods of the bumblebees to L. japonicus flowers reciprocally differed between B. deuteronymus and B. terrestris, suggesting phenological resource partitioning between these species. Our study suggests that phenological niche partitioning is more common in specialized flowers (L. japonicus) than in generalized flowers (R. rugosa).     

Bee pollination and evidence of substitutive nectary in <Emphasis Type="Italic">Anadenanthera colubrina</Emphasis> (Leguminosae-Mimosoideae)

Anadenanthera colubrina (Vell.) Brenan (Leguminosae-Mimosoideae) is a widely-distributed tree in seasonally dry tropical forests of South America that was classified previously as lacking nectaries. However, some studies have stated that its flowers produce nectar, while others analyzed the composition of unifloral honey produced from A. colubrina flowers, raising the question about nectar production in the species. We studied the pollination and reproductive biology of A. colubrina var. cebil (Griseb.) Altschul in a natural population in the Caatinga, northeastern Brazil. Reproductive phenology, sexual system, floral biology, resource, and pollinators were investigated. We analyzed the breeding system through controlled pollinations for addressing its dependence on pollen vectors for reproduction. Anadenanthera colubrina flowered in the dry season, flower heads are heteromorphic, with staminate flowers at the base and perfect flowers at the apex of the inflorescence, characterizing andromonoecy. Anthesis is diurnal. We observed small drops of nectar at the apex of the petals of some flowers per inflorescence. Together with observations on flower visitor behavior and histochemical tests, we propose that A. colubrina produces floral nectar at the apex of the corolla, characterizing a substitutive nectary (sensu Vogel). This is the first record of substitutive nectary in the Mimosoideae and the first record of andromonoecy in the genus. Bees were the main pollinators (higher frequency), although other insects such as wasps, butterflies, and small beetles were also observed collecting nectar and/or pollen. The species is self-incompatible, thus depending on insect pollen vectors, mainly bees, for reproduction.     

Co-dependency between a specialist <Emphasis Type="Italic">Andrena</Emphasis> bee and its death camas host, <Emphasis Type="Italic">Toxicoscordion paniculatum</Emphasis>

Among associations of plants and their pollinating bees, mutually specialized pairings are rare. Typically, either pollen specialist (oligolectic) bees are joined by polylectic bees in a flowering species’ pollinator guild, or specialized flowers are pollinated by one or more polylectic bees. The bee Andrena astragali is a narrow oligolege, collecting pollen solely from two nearly identical species of death camas (Toxicoscordion, formerly Zigadenus). Neurotoxic alkaloids of these plants are implicated in sheep and honey bee poisoning. In this study, T. paniculatum, T. venenosum and co-flowering forbs were sampled for bees at 15 sites along a 900-km-long east–west transect across the northern Great Basin plus an altitudinal gradient in northern Utah’s Bear River Range. Only A. astragali bees were regularly seen visiting flowering panicles of these Toxicoscordion. In turn, this bee was never among the 170 bee species caught at 17 species of other prevalent co-occurring wildflowers in the same five state region (38,000 plants surveyed). Our field pollination experiments show that T. paniculatum is primarily an outcrosser dependent on pollinator visitation for most capsule and seed set. Thus, both A. astragali and two sister species of Toxicoscordion are narrowly specialized and co-dependent on each other for reproduction, illustrating a rare case of obligate mutual specialization in bee–plant interactions.     

Temporal changes in floral resource availability and flower visitation in a butterfly

Foraging affects survival and reproductive success in animals, including flower-visiting insects. Plant-derived floral food resources (i.e. nectar and pollen) may be rapidly changing in space and time and pollinators may need to quickly switch to new resources. Butterflies are suitable model organisms to investigate foraging behaviour of insect pollinators, because they can be easily monitored under natural conditions. We studied flower visitation patterns in the Clouded Apollo butterfly Parnassius mnemosyne in relation to the abundance of available floral resources. We recorded flower visitation daily in individually marked butterflies, listed flowering species and estimated flower abundance categories every 3 days in a single meadow, during five consecutive flight periods. Butterflies visited 35 nectar plants from the 71 species available. Few nectar plants were frequently visited (visit ratios for the annually most visited species: 37–60%), many were scarcely visited and no visits were observed on several abundant species. Flower abundance and visit ratio varied among years and within flight periods. The number of visits increased with flower abundance in the seven most frequently visited plant species, but not in the occasionally visited ones. Beside their choosiness, Parnassius mnemosyne butterflies were able to adjust foraging behaviour to rapidly changing resource distributions. Diet selectivity in adults might increase the vulnerability of this species. However, visitation plasticity may mitigate the effect of the lack of some nectar plants, as complementary resources can be used as alternatives.     

Association between floral traits and rewards in Erysimum mediohispanicum (Brassicaceae)

Background and Aims

Floral rewards may be associated with certain morphological floral traits and thus act as underlying factors promoting selection on these traits. This study investigates whether some traits that are under pollinator-mediated selection (flower number, stalk height, corolla diameter, corolla tube length and corolla tube width) in the Mediterranean herb E. mediohispanicum (Brassicaceae) are associated with rewards (pollen and nectar).

Methods

During 2005 the phenotypic traits and the visitation rate of the main pollinator functional groups were quantified in 720 plants belonging to eight populations in south-east Spain, and during 2006 the same phenotypic traits and the reward production were quantified in 400 additional plants from the same populations.

Key Results

A significant correlation was found between nectar production rate and corolla tube length, and between pollen production and corolla diameter. Visitation rates of large bees and butterflies were significantly higher in plants exhibiting larger flowers with longer corolla tubes.

Conclusions

The association between reward production and floral traits may be a factor underlying the pattern of visitation rate displayed by some pollinators.Key words: Erysimum, floral traits, nectar, pollen, pollinator visitation rate, reward     

Flowering phenology and potential pollen emission of three <Emphasis Type="Italic">Artemisia</Emphasis> species in relation to airborne pollen data in Poznań (Western Poland)

Artemisia pollen is an important allergen in Europe. In Poznań (Western Poland), three Artemisia species, A. vulgaris, A. campestris and A. absinthium, are widely distributed. However, the contributions of these species to the total airborne pollen are unknown. The aim of the study was to determine the flowering phenology and pollen production of the three abovementioned species and to construct a model of potential Artemisia pollen emission in the study area. Phenological observations were conducted in 2012 at six sites in Poznań using a BBCH phenological scale. Pollen production was estimated by counting the pollen grains per flower and recalculating the totals per inflorescence, plant and population in the study area. Airborne pollen concentrations were obtained using a Hirst-type volumetric trap located in the study area. Artemisia vulgaris began to flower the earliest, followed by A. absinthium and then A. campestris. The flowering of A. vulgaris corresponded to the first peak in the airborne pollen level, and the flowering of A. campestris coincided with the second pollen peak. The highest amounts of pollen per single plant were produced by A. vulgaris and A. absinthium. A. campestris produced considerably less pollen, however, due to its common occurrence, it contributed markedly (30 %) to the summation of total of recorded pollen. A. vulgaris is the most important pollen source in Poznań, but the roles of two other Artemisia species cannot be ignored. In particular, A. campestris should be considered as an important pollen contributor and likely might be one of the main causes of allergic reactions during late summer.     

<Emphasis Type="Italic">Apis mellifera</Emphasis> and <Emphasis Type="Italic">Osmia cornuta</Emphasis> as carriers for the secondary spread of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> on apple flowers

The efficiency of two pollinators, Apis mellifera L. (Hymenoptera: Apidae) and the mason bee Osmia cornuta (Latreille) (Hymenoptera: Megachilidae), as carriers of biocontrol agents (BCA) from flower to flower (secondary colonisation) was investigated on apple cv ‘Golden Delicious’. The BCA tested was Bacillus subtilis, strain BD170 (Biopro®) developed for the control of the ‘fire blight’ caused by Erwinia amylovora (Burril) Winslow et al. The two insect species were studied as secondary BCA carriers on apple plants in pots under net screened tunnels. Their behaviour and capacity to deposit the BCA in the most receptive flower parts were compared both by washing, diluting and plating the flower organs on a recovery medium and by means of PCR analyses based on a molecular marker. O. cornuta showed better performances with respect to A. mellifera. For the field trials, pollinators were introduced in four apple orchards. During apple’s flowering, the BD170 (100 g hl^?l) was sprayed once in two fields, and twice in the others. The pollinators’ efficacy in carrying the BCA from sprayed flowers to the stigmas of newly opened ones at different times after the spray treatment was evaluated. The detection of the BCA was performed by PCR analysis. The percentages of positive PCR flower samples were higher in the internal treated areas of the fields with respect to the external untreated ones, but the high colonisation level found in the latter and in the flowers opened in both areas several days after the treatment(s) demonstrated that pollinators can play an important role as secondary carriers.     

Low interspecific pollen transfer between invasive aquatic <Emphasis Type="Italic">Ludwigia grandiflora</Emphasis> and native co-flowering plants

Showy invasive alien plants are often integrated in the diet of generalist pollinators and because of the lack of co-evolvement with the native plant community, a high amount of interspecific pollen transfer (IPT) can be expected. We investigated pollinator switching and magnitude plus distance of IPT between the alien aquatic Ludwigia grandiflora and the native Lythrum salicaria in both directions in uninvaded and invaded sites with a different relative abundance of L. grandiflora (% cover of the alien plant: no cover; low cover: <5%; high cover: 50–75%). A field experiment was conducted to include both pollinator interspecific movements and tracking of IPT, using fluorescent dye as a pollen analogue. Despite a substantial overlap in pollinators between L. grandiflora and the native L. salicaria, less than 10% of the observed flights were interspecific. Similar results were found in dye transfer patterns. The proportions of stigmas with conspecific dye were always higher than the proportions of stigmas with heterospecific dye for L grandiflora and L. salicaria. There were no differences in conspecific dye loads for L. salicaria between uninvaded and invaded sites. Conspecific pollen loss (native CPL) and heterospecific pollen deposition (alien HPD) were in general low and species-specific. The distance of HPD ranged respectively from 1.7 to 39 m and from 0.3 to 54.8 m in the low cover and high cover sites while CPL ranged respectively from 6.40 to 68.02 m and from 0.60 to 40.18 m in the low cover and high cover sites. We can conclude that, in this system, CPL and HPD will play a minor role in pollinator-mediated interaction. Furthermore, interspecific competition for pollinators will cover a larger distance than just neighboring individuals. Our results suggest the necessity to consider the combined effect of insect visitation, pollen deposition, relative alien abundance, distance and seed set when investigating pollinator-mediated interactions of invasive plants.     

Comparative pollinator limitation of two non-native shrubs: do mutualisms influence invasions?

While interactions between invaders and resident species have received a great deal of attention recently, the role of mutualists in facilitating or constraining invasions is rarely considered. We investigated the reproductive ecology of two closely related, woody legumes, Cytisus scoparius (Scotch broom) and Genista monspessulana (French broom), invading the same sites. Both species are considered noxious non-native weeds in California, and are considered to be ecologically similar, but Genista has much smaller flowers than Cytisus. Neither species showed appreciable levels of autogamous selfing. When experimentally self-pollinated, Genista demonstrated less depression of fruit set and seed set relative to outcrossed flowers than did Cytisus. At two sites on the Marin peninsula, Calif., Genista flowers were consistently less likely to be pollinated than Cytisus flowers. Genista was significantly pollen limited at both sites, while Cytisus was pollen limited at only the site with lower visitation rates. In the three populations with demonstrable pollen limitation, we found a significant relationship between fruit production and natural pollinator visitation at the level of the individual plant. However, we did not find that overall patterns of fecundity were strongly predicted by differences in pollen limitation between species or between sites. While a previous study found a tight link between patterns of pollinator visitation and patterns of reproduction in Cytisus in Washington State, we conclude that a more complex and variable environment (in terms of resources, herbivores, and florivores) on the Marin Peninsula de-coupled the relationship between pollinators and fruit production in these invaders. Our results suggest that the role of mutualisms in promoting or constraining invasions is likely to vary considerably among invaded communities.     

Floral micromorphology of the Australian carnivorous bladderwort <Emphasis Type="Italic">Utricularia dunlopii</Emphasis>, a putative pseudocopulatory species

Flowers of sexually deceptive taxa generally possess a set of morphological and physiological characters that mimic their insect pollinators. These characters often include a specific insect-like floral configuration, together with scent glands (osmophores) that produce fragrances which chemically resemble insect sex pheromones. Furthermore, these flowers tend not to produce pollinator food rewards. According to some authors, flowers of the Australian bladderwort Utricularia dunlopii (and species of the Utricularia capilliflora complex) resemble insects, and pollination perhaps occurs by pseudocopulation. The aims of this paper are to compare the structure and distribution of floral glandular trichomes in the Australian carnivorous plant U. dunlopii with those of closely related species assigned to the same section and to discuss their putative function. Floral tissues of U. dunlopii P. Taylor, Utricularia paulinae Lowrie, Utricularia dichotoma Labill. and Utricularia uniflora R.Br. (section Pleiochasia) were investigated using light microscopy, scanning electron microscopy, transmission electron microscopy and histochemistry. In U. dunlopii, two long, erect, filiform appendages arising from the upper lip of the corolla, together with three arising from the lower lip, bear numerous glandular trichomes that may function as osmophores. In other species, such as U. uniflora and U. paulinae, glandular papillae on the corolla palate may also function as osmophores. The floral anatomical and morphological organisation of U. dunlopii differs from that of the other investigated species, indicating that its insect pollinators are also likely to differ. Morphological and ultrastructural observations, while generally contributing to our understanding of the flower of U. dunlopii, do not refute the possibility that pollination here may occur by pseudocopulation. Further field-based investigations, however, are now necessary to test this hypothesis.     

Micromorphological and histochemical attributes of flowers and floral reward in <Emphasis Type="Italic">Linaria vulgaris</Emphasis> (Plantaginaceae)

The self-incompatible flowers of Linaria vulgaris have developed a range of mechanisms for attraction of insect visitors/pollinators and deterrence of ineffective pollinators and herbivores. These adaptive traits include the flower size and symmetry, the presence of a spur as a “secondary nectar presenter,” olfactory (secondary metabolites) and sensual (scent, flower color, nectar guide—contrasting palate) signals, and floral rewards, i.e. pollen and nectar. Histochemical tests revealed that the floral glandular trichomes produced essential oils and flavonoids, and pollen grains contained flavonoids, terpenoids, and steroids, which play a role of olfactory attractants/repellents. The nectary gland is disc-shaped and located at the base of the ovary. Nectar is secreted through numerous modified stomata. Nectar secretion began in the bud stage and lasted to the end of anthesis. The amount of produced nectar depended on the flower age and ranged from 0.21 to 3.95 mg/flower (mean?=?1.51 mg). The concentration of sugars in the nectar reached up to 57.0%. Both the nectar amount and sugar concentration demonstrated a significant year and population effect. Pollen production was variable between the years of the study. On average, a single flower of L. vulgaris produced 0.31 mg of pollen. The spectrum of insect visitors in the flowers of L. vulgaris differed significantly between populations. In the urban site, Bombus terrestris and Apis mellifera were the most common visitors, while a considerable number of visits of wasps and syrphid flies were noted in the rural site.     

Investigating the floral and reproductive biology of the endangered microendemic cactus <Emphasis Type="Italic">Uebelmannia buiningii</Emphasis> Donald (Minas Gerais,Brazil)

The Cactaceae are known to be amongst the most endangered plant families of the world due to reduction of their habitats and activities of collectors. As the species of the family are dependent on animals to perform cross pollination, and hence seed production, their population performance may be further negatively affected by interrupted biotic interactions. For efficient conservation of rare species, knowledge on reproductive biology and pollinators is of prime importance. In our study we focused on Uebelmannia buiningii Donald, a microendemic cactus from the Serra Negra State Park, Minas Gerais state, Brazil. During four field expeditions to three localities of the species between September 2012 and September 2013, we measured flowers, detected nectar-guides and osmophores and performed pollen viability tests. We studied the reproductive system of the species using manual self- and cross-pollination tests and observed pollinators. Our results revealed that the flowering period takes place during the dry season, between April and October, and that the diurnal flowers open between 7:00 a.m. and 5 p.m. The flowers are shortly tubular with yellow perianth-segments. We found neither nectar nor nectar-guides, and osmophores appeared as glands within the flower tube. Whereas pollen viability was 90.25%, manual cross-pollination tests have shown cross-pollination with gametophytic incompatibility. We observed two bee species visiting the flowers and acting as effective pollinators: Dialictus opacus and Plebeia sp. The combination of low reproductive activity with gametophytic incompatibility, together with the reduced number of individuals in a population and low number of populations, makes the endemic cactus U. buiningii a critically endangered species.     

Effects of insecticide application on parasitism rates of pollen beetle larvae (<Emphasis Type="Italic">Brassicogethes aeneus</Emphasis> (Fabricius)) by tersilochine parasitoids

Larval parasitoids can substantially reduce the population density of the pollen beetle [Brassicogethes aeneus (Fabricius), syn. Meligethes aeneus (Fabricius)]. The most abundant tersilochine parasitoids of pollen beetle are Tersilochus heterocerus, Phradis interstitialis and P. morionellus. The main activity of these parasitoids was observed in the period shortly before flowering to full flowering of oilseed rape. Insecticide applications during this period may have negative effects on parasitoids. In the present study, the effects of the insecticides Biscaya (a.i. thiacloprid), Mavrik (a.i. tau-fluvalinate) and Karate Zeon (a.i. lambda-cyhalothrin) applied during the bud or flowering stage of winter oilseed rape on parasitization of pollen beetle larvae by T. heterocerus were studied in 12 field trials at different locations in Germany in 2013–2015. The effects on parasitism by Phradis spp. were assessed in 2015. Parasitism of pollen beetle larvae by T. heterocerus was found in all field trials in all experimental years, but in most trials not before full flowering. Maximum percentage of parasitized larvae at different locations ranged between 3.4 and 16.8% in 2013, 8.3 and 22.4% in 2014 and from 11.1 to 29.1% in 2015. Levels of parasitism were not significantly different between the untreated control and insecticide treatments within each location. In contrast to T. heterocerus, Phradis spp. was not detected at all locations and not before flowering declining. In field trials at Lucklum and Puch, the maximum level of parasitism by Phradis spp. was 9.4 and 18.3%, respectively. No significant effect of insecticide application on parasitism by Phradis spp. was observed between the treatments. The results of this study showed that the insecticides used in the field trials did not affect parasitization of pollen beetle larvae by T. heterocerus and Phradis spp., regardless whether applied at the bud stage, at the beginning of flowering or full flowering.     

Pollen load diversity and foraging niche overlap in a pollinator community of the rare <Emphasis Type="Italic">Dictamnus albus</Emphasis> L.

Bees collect pollen as an important resource for offspring development while acting as pollen vectors for the plants visited. Foraging preferences of pollinators together with plant species availability shape the web of interactions at the local scale. In this study, we focused on the bee pollinator community of a population of the rare protected perennial herb Dictamnus albus, with the aim to characterise the pollen preferences and the foraging niche overlap among species through time. Bees were sampled during four consecutive years in a natural population of D. albus, throughout the blooming period of the plant species. We performed an analysis of insect pollen loads to investigate the interactions with the study species and the co-flowering plants in the area, and to evaluate the degree of foraging overlap among pollinators. Over the study years, all bee species showed a high fidelity to D. albus (60–80%), even if some taxa preferentially collected pollen from other flowering species. The foraging niche overlap in the pollinator community decreased together with an increased diversity of co-flowering plant species. The results obtained indicate that bees preferentially forage on D. albus in the studied area, but that co-flowering species contribute to complement their diet and likely reduce competition for foraging resources. It appears therefore important to maintain a high diversity of co-flowering plants to preserve the diversity in the studied pollinator community of D. albus.     

A new <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> deletion mutant <Emphasis Type="Italic">apetala1-20</Emphasis>

A new deletion allele of the APETALA1 (AP1) gene encoding a type II MADS-box protein with the key role in the initiation of flowering and development of perianth organs has been identified in A. thaliana. The deletion of seven amino acids in the conserved region of the K domain in the ap1-20 mutant considerably delayed flowering and led to a less pronounced abnormality in the corolla development compared to the weak ap1-3 and intermediate ap1-6 alleles. At the same time, a considerable stamen reduction has been revealed in ap1-20 as distinct from ap1-3 and ap1-6 alleles. These data indicate that the K domain of AP1 can be crucial for the initiation of flowering and expression regulation of B-class genes controlling stamen development.     

Nectar production,reproductive success and the evolution of generalised pollination within a specialised pollen-rewarding plant family: a case study using <Emphasis Type="Italic">Miconia theizans</Emphasis>

Generalist plant–pollinator interactions are prevalent in nature. Here, we untangle the role of nectar production in the visitation and pollen release/deposition in Miconia theizans, a nectar-rewarding plant within the specialised pollen-rewarding plant family Melastomataceae. We described the visitation rate, nectar dynamics and pollen release from the poricidal anthers and deposition onto stigmas during flower anthesis. Afterwards, we used a linear mixed model selection approach to understand the relationship between pollen and nectar availability and insect visitation rate and the relationship between visitation rate and reproductive success. Miconia theizans was visited by 86 insect species, including buzzing and non-buzzing bees, wasps, flies, hoverflies, ants, beetles, hemipterans, cockroaches and butterflies. The nectar produced explained the visitation rate, and the pollen release from the anthers was best explained by the visitation rate of pollinivorous species. However, the visitation rates could not predict pollen deposition onto stigmas. Nectar production may explain the high insect diversity and led to an increase in reproductive success, even with unpredictable pollen deposition, indicating the adaptive value of a generalised pollination system.