Pollination of the cycad <Emphasis Type="Italic">Zamia incognita</Emphasis> A. Lindstr. &amp; Idárraga by <Emphasis Type="Italic">Pharaxonotha</Emphasis> beetles in the Magdalena Medio Valley,Colombia: a mutualism dependent on a specific pollinator and its significance for conservation

The genus Zamia (Zamiaceae: Cycadales) exhibits its greatest diversity in Colombia and is highly threatened by habitat loss, extraction for ornamental plant trade, and mining, among other factors. One of the most important considerations for the effective conservation of Zamia is its highly specialized reproductive biology. Despite the importance of pollination for the populations’ viability, no studies have examined the pollination process of cycads in Colombia. Herein, we describe the pollination process of Zamia incognita A. Lindstr. & Idárraga, in a natural population. Exclusion experiments were performed by selectively excluding wind, beetles, both, or neither, which demonstrated that Pharaxonotha beetles are effective pollinators of Zamia incognita and that wind does not play any role as pollen vector. By following beetles marked with fluorescent dyes and directly observing beetle movements on and into female cones and micropyles, we confirmed that Pharaxonotha sp. is the effective pollinator of Z. incognita. The beetles traveled a maximum dispersal distance from a male to female cone of nearly 22 m and a minimum distance of 5 m. We found Pharaxonotha beetles in male cones, where they complete their life cycle. Cones produce heat in a circadian pattern associated with the elongation of the cones and pollen shedding. The increase in cones’ temperature appears to play an important role in beetle attraction. We suggest that pollination droplets on the micropyles would be a reward to pollinators. We also discuss the relationship of this Zamia species with other insects, which have important consequences for the conservation of web interactions.     

Bamboo flowers visited by insects: do insects play a role in the pollination of bamboo flowers?

Relatively little is known about pollination and other aspects of the reproductive biology of bamboos, but wind pollination is assumed to be the rule, at least in woody bamboos. Documenting the reproductive biology of woody bamboos is a complex task due to the long periods of time between flowering cycles, which range from 3 to 120 years. Insects visiting Guadua paniculata and G. inermis flowers were collected in the field. Scanning electron micrographs were taken of the visiting insects. Four species of bees, three from tribe Meliponini (Geotrigona acapulconis, Plebeia frontalis and Trigona fulviventris) and one from tribe Apini (Apis mellifera), along with a syrphid fly (Toxomerus teligera) were found visiting bamboo flowers. Some species of Hemiptera were also found feeding on the flowers, such as Neortholomus jamaicensis (Lygaeidae), or preying on the flower visitors (Apiomerus pictipes (Reduviidae)). Insects visiting bamboo inflorescences may facilitate the release of pollen grains into the air, promoting outcrossing and genetic flow among the individuals of the flowering bamboo populations.     

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.     

Pollen movement by the bat <Emphasis Type="Italic">Artibeus jamaicensis</Emphasis> (Chiroptera) in an agricultural landscape in the Yucatan Peninsula,Mexico

Artibeus jamaicensis is a medium-sized frugivorous microchiropteran bat that complements its diet with nectar and pollen during the dry season. We investigated which species of pollen are carried by A. jamaicensis in order to determine its potential role as a plant pollinator in the northern Yucatan Peninsula. We collected pollen from the fur of 192 individuals throughout the year from April 2004 to March 2005. We recorded pollen from nine plant species of eight families and found five unidentified pollen types, with the highest pollen species richness recorded in June. A. jamaicensis moved pollen of Erythrina standleyana and Mimosa bahamensis, which have not hitherto been reported as visited by this species. The most abundant pollen in the samples was found to be that of three tree species: Ceiba pentandra, C. aesculifolia and Lysiloma latisiliquum. Very few samples contained pollen in the rainy season, when the bats fed mainly on fruits. A. jamaicensis can fly several kilometres among foraging locations and dispersed large amounts of pollen from tree species growing near cenotes as well as those not present at cenotes but occurring in other forest fragments, highlighting its importance as a pollen vector among forest fragments in the largely deforested landscape of the Yucatan Peninsula, helping to reduce the negative effects of forest fragmentation. Ceiba appears to benefit from the role of A. jamaicensis as a pollen vector, and the species play an important ecological role in the Yucatán landscape, supplying shade, nectar and fruit for wildlife.     

Centromeric and non-centromeric satellite DNA organisation differs in holocentric <Emphasis Type="Italic">Rhynchospora</Emphasis> species

Satellite DNA repeats (or satDNA) are fast-evolving sequences usually associated with condensed heterochromatin. To test whether the chromosomal organisation of centromeric and non-centromeric satDNA differs in species with holocentric chromosomes, we identified and characterised the major satDNA families in the holocentric Cyperaceae species Rhynchospora ciliata (2n = 10), R. globosa (2n = 50) and R. tenuis (2n = 2x = 4 and 2n = 4x = 8). While conserved centromeric repeats (present in R. ciliata and R. tenuis) revealed linear signals at both chromatids, non-centromeric, species-specific satDNAs formed distinct clusters along the chromosomes. Colocalisation of both repeat types resulted in a ladder-like hybridisation pattern at mitotic chromosomes. In interphase, the centromeric satDNA was dispersed while non-centromeric satDNA clustered and partly colocalised to chromocentres. Despite the banding-like hybridisation patterns of the clustered satDNA, the identification of chromosome pairs was impaired due to the irregular hybridisation patterns of the homologues in R. tenuis and R. ciliata. These differences are probably caused by restricted or impaired meiotic recombination as reported for R. tenuis, or alternatively by complex chromosome rearrangements or unequal condensation of homologous metaphase chromosomes. Thus, holocentricity influences the chromosomal organisation leading to differences in the distribution patterns and condensation dynamics of centromeric and non-centromeric satDNA.     

Embryological peculiarities of interspecific hybridization in <Emphasis Type="Italic">Pinus sibirica</Emphasis>

Cytoembryological research of the ovules in experiments with interspecific hybridization of Pinus sibirica (pollination be the pollen of P. koraiensis, P. armandii, P. parviflora, P. strobus, P. hokkaidensis, P. wallichiana, P. monticola, and P. сembra) revealed that the development of megagametophytes occurred in them by the usual scenario and resulted in the formation of mature archegonia. Pollen successfully germinated on the nucellus of ovules. However, disturbances were observed in the process of male gametophyte development, and pollen tubes on the nucellus were not visible by the period of archegonia maturation. Fertilization was usually absent. The development of embryonic channel is determined by egg cell maturity. The only exception was the variant of the controlled pollination of Pinus sibirica × P. сembra, in which the embryo has been formed.     

The floral biology and reproductive system of <Emphasis Type="Italic">Mauritia flexuosa</Emphasis> (Arecaceae) in a restinga environment in northeastern Brazil

Studies of the floral biology of the buriti palm, Mauritia flexuosa, have presented conflicting results with respect to the mechanism of pollination, indicating either cantharophily or anemophily. To resolve this question, the floral biology of M. flexuosa was studied in a coastal restinga environment in northeastern Brazil. The reproductive system was studied experimentally, and floral visitors were collected by bagging inflorescences. In this environment, M. flexuosa, a dioecious species, has several gender-specific floral features that function to attract pollinators, especially beetles. The male flowers produce large amounts of pollen as a reward, and male and female inflorescences produce similar odors that attract pollinators to female flowers, which offer only a nectar secretion as a reward. When feeding on the female flowers, the visitors frequently come into contact with the stigmata. To increase the chances of pollination, the female flowers persist longer than the male ones, and the viability of the pollen grain is very high. A curculionid beetle species of the genus Grasidius was found to be an effective pollinator. We suspect that wind also contributes to the pollination of M. flexuosa in the study area, but in a relatively minor way.     

Identification,isolation and expression analysis of eight stress-related <Emphasis Type="Italic">R2R3</Emphasis>-<Emphasis Type="Italic">MYB</Emphasis> genes in tartary buckwheat (<Emphasis Type="Italic">Fagopyrum tataricum</Emphasis>)

Key message

Eight R2R3 - MYB genes in tartary buckwheat were identified, and their expression patterns were comprehensively analyzed, which reveals role in plant response to abiotic stresses.

Abstract

The proteins of the R2R3-MYB superfamily play key roles in the growth and development processes as well as defense responses in plants. However, their characteristics and functions have not been fully investigated in tartary buckwheat (Fagopyrum tataricum), a strongly abiotic resistant coarse cereal. In this article, eight tartary buckwheat R2R3-MYB genes were isolated with full-length cDNA and DNA sequences. Phylogenetic analysis of the members of the R2R3-MYB superfamily between Arabidopsis and tartary buckwheat revealed that the assumed functions of the eight tartary buckwheat R2R3-MYB proteins are divided into five Arabidopsis functional subgroups that are involved in abiotic stress. Expression analysis during abiotic stress and exogenous phytohormone treatments identified that the eight R2R3-MYB genes responded to one or more treatments. This study is the first comprehensive analysis of the R2R3-MYB gene family in tartary buckwheat under abiotic stress.

     

Nectar thieves or invited pollinators? A case study of tansy flowers and common house mosquitoes

Mosquitoes are generally considered nectar thieves that do not contribute to the pollination of the flowers they visit. Here we tested the hypothesis that the common house mosquito, Culex pipiens, contributes to the pollination of tansies, Tanacetum vulgare, and possibly the pollination of other members of the Asteraceae (Achillea millefolium, Leucanthemum vulgare, Solidago canadensis). To test this hypothesis, we (1) field-collected mosquitoes probing inflorescences of T. vulgare, A. millefolium, and L. vulgare, and recorded the number and distribution of pollen grains on their bodies, (2) exposed laboratory-reared Cx. pipiens to inflorescences of T. vulgare, A. millefolium, and S. canadensis, and (3) ran pollination experiments with Cx. pipiens and T. vulgare in a greenhouse. We found (1) that 41 of 164 field-collected Cx. pipiens carried pollen, (2) that 48, 34, and 34 % of Cx. pipiens accumulated pollen from T. vulgare, A. millefolium, and S. canadensis, respectively, during floral visits of greenhouse-grown specimens, and (3) that cross-pollination by Cx. pipiens resulted in significant seed set of T. vulgare in pollination experiments. Based on our observations that Cx. pipiens are frequent floral visitors and are able to carry pollen and to induce seed set in T. vulgare, it is clear that Cx. pipiens plays a role in the pollination of T. vulgare, and possibly other members of the Asteraceae.     

Ant pollination of <Emphasis Type="Italic">Syzygium occidentale</Emphasis>, an endemic tree species of tropical rain forests of the Western Ghats,India

Although mutualism between ants and flowering plants is wide spread, ant pollination has not evolved as a major pollination syndrome. So far ant pollination has been reported largely in herbaceous species, growing in warm and dry habitats. While studying pollination ecology of Syzygium species (Myrtaceae), growing in tropical forests of the Western Ghats, India, we observed one of the ant species, Technomyrmex albipes, to be the dominant floral visitor in S. occidentale (Bourd.) Chithra among a range of other insect (species of Xylocopa and Trigona, and Apis cerana) and bird visitors. We studied the role of ant species in pollination when compared to other floral visitors. The fruit set in flowers exclusively visited by T. albipes was significantly higher than those visited by any other visitor. The day and night exclusive pollination experiments allowing only T. albipes indicated diel pollination by T. albipes, which was the only active flower visitor during the night. The breeding system of the species was studied through controlled pollinations. The species is partially self-compatible and exhibits considerable autogamy.     

Intersexual mimicry and flowering phenology facilitate pollination in a dioecious habitat specialist species, <Emphasis Type="Italic">Myristica fatua</Emphasis> (Myristicaceae)

Myristica fatua is a dioecious specialist species restricted to the endangered, freshwater Myristica swamp forests in the Western Ghats, India. Earlier studies have alluded to pollination by deception in members of the Myristica genus, and thus we examined the pollination ecology comprising floral biology, flower production, flower visitors, and reproductive success in M. fatua and inferred the potential strategies that could permit such deception in this habitat specialist tree. Male flowers provide pollen rewards for an extended period of time while female flowers are rewardless and both sexes are visited by generalist insects, mainly by honeybees and stingless bees. Bee visits were significantly more frequent and longer on male than on female flowers as bees collected pollen from male flowers. We found that flower production patterns create a preponderance of males compared to females in the swamp populations. Using a model of honeybee color vision, we found the distance between the color loci of male and female flowers and based on minimum visual angle subtended by these flowers, we suggest that the two floral sexes cannot be discriminated by bees. Bees are likely deceived by the perceptual similarity of rewardless female flowers to pollen-offering male flowers and pollination is the consequence of foraging errors made by pollinators that encounter largely male–rarely female flower mosaics as they forage among clump-distributed M. fatua trees in the swamp habitat.     

First aerobiological study in Mediterranean part of Croatia (Dalmatia): pollen spectrum and seasonal dynamics in the air of Split

The aim of this study was to investigate aerobiological dynamics of pollen in the Mediterranean part of Croatia in the air of the city of Split. Pollen monitoring during the period from 2005 to 2013 was performed using a Hirst volumetric trap. Among the identified pollen of 50 taxa, 21 were allergenic. The average annual pollen index was 33,513. Three pollination seasons were established: early winter season dominated by tree pollen, spring–summer season dominated by herbaceous plants and summer–autumn season with lower amounts of Parietaria and Cupressaceae pollen. According to the abundance, the main taxa were: Cupressaceae, Parietaria/Urtica, Pinus, Quercus, Olea, Carpinus/Ostrya, Poaceae, Platanus and Ambrosia. The annual pollen index together with the daily maximum concentrations showed an upward trend for selected taxa during the study period. The highest monthly pollen index and the highest biodiversity were recorded in April and the lowest during the late autumn and winter months. The pollen calendar created for the city of Split confirmed Mediterranean features of the pollen spectrum. The longest pollen seasons were recorded for Cupressaceae, Parietaria/Urtica and Poaceae pollen types. The correlations between pollen concentrations and meteorological parameters were analyzed. The correlations between pollen concentrations and temperature were positive, while the humidity and the precipitation mostly showed negative influence.     

Pollination-system diversity in <Emphasis Type="Italic">Epipactis</Emphasis> (Orchidaceae): new insights from studies of <Emphasis Type="Italic">E. flava</Emphasis> in Thailand

The rewarding orchid Epipactis flava was studied in NW Thailand. Its flowers were visited by a wide range of insects, most of which served as pollinators. The most frequent pollen bearers were (in decreasing order): the cricket Homoeoxipha lycoides, stingless bees of the Tetragonula testaceitarsis/hirashimai complex, hoverflies of subfam. Syrphinae, the wasp Polybioides gracilis and sweat bees of subfam. Halictinae. We found no evidence of a link between the rheophytic habit of E. flava and its pollinator fauna. Whereas most pollinators visited the flowers to feed on nectar, females of Episyrphus alternans (Syrphidae: Syrphinae) were observed to oviposit despite the absence of prey for their young. Hence, we suggest that dual pollination systems contribute to the opportunist strategy of E. flava, and we discuss, in a phylogenetic framework, how the strategy fits in with those previously reported for Epipactis sect. Arthrochilium. The elastic attachment of the epichile (a universal trait in sect. Arthrochilium) was found to promote outcrossing, and we hypothesize that loss of the elastic hinge has provided a key innovation facilitating recurrent evolution of obligate autogamy in sect. Epipactis (which is nested in sect. Arthrochilium).     

<Emphasis Type="Italic">Cannabis</Emphasis> is indigenous to Europe and cultivation began during the Copper or Bronze age: a probabilistic synthesis of fossil pollen studies

Conventional wisdom states Cannabis sativa originated in Asia and its dispersal to Europe depended upon human transport. Various Neolithic or Bronze age groups have been named as pioneer cultivators. These theses were tested by examining fossil pollen studies (FPSs), obtained from the European Pollen Database. Many FPSs report Cannabis or Humulus (C/H) with collective names (e.g. Cannabis/Humulus or Cannabaceae). To dissect these aggregate data, we used ecological proxies to differentiate C/H pollen, as follows: unknown C/H pollen that appeared in a pollen assemblage suggestive of steppe (Poaceae, Artemisia, Chenopodiaceae) we interpreted as wild-type Cannabis. C/H pollen in a mesophytic forest assemblage (Alnus, Salix, Populus) we interpreted as Humulus. C/H pollen curves that upsurged and appeared de novo alongside crop pollen grains we interpreted as cultivated hemp. FPSs were mapped and compared to the territories of archaeological cultures. We analysed 479 FPSs from the Holocene/Late Glacial, plus 36 FPSs from older strata. The results showed C/H pollen consistent with wild-type C. sativa in steppe and dry tundra landscapes throughout Europe during the early Holocene, Late Glacial, and previous glaciations. During the warm and wet Holocene Climactic Optimum, forests replaced steppe, and Humulus dominated. Cannabis retreated to steppe refugia. C/H pollen consistent with cultivated hemp first appeared in the Pontic-Caspian steppe refugium. GIS mapping linked cultivation with the Copper age Varna/Gumelni?a culture, and the Bronze age Yamnaya and Terramara cultures. An Iron age steppe culture, the Scythians, likely introduced hemp cultivation to Celtic and Proto-Slavic cultures.     

Floral divergence and temporal pollinator partitioning in two synchronopatric species of <Emphasis Type="Italic">Vigna</Emphasis> (Leguminosae-Papilionoideae)

Exclusivity of pollinators, temporal partitioning of shared pollinators and divergence in pollen placement on the shared pollinators’ bodies are mechanisms that prevent interspecific pollen flow and minimize competitive interactions in synchronopatric plant species. We investigated the floral biology, flower visitors, pollinator effectiveness and seasonal flower availability of two syntopic legume species of the genus Vigna, V. longifolia and V. luteola, in ‘restinga’ vegetation of an island in southern Brazil. Our goal was to identify the strategies that might mitigate negative consequences of their synchronous flowering. Vigna longifolia and V. luteola were self-compatible, but depended on pollinators to set seeds. Only medium to large bees were able to trigger the ‘brush type’ pollination mechanism. Vigna longifolia, with its asymmetrical corolla and hugging mechanism, showed a more restrictive pollination system, with precise sites of pollen deposition/removal on the bee’s body, compared to V. luteola, with its zygomorphic corolla and cymbiform keel. There was a daily temporal substitution in flower visitation by the main pollinators. Vigna longifolia and V. luteola had overlapping flowering phenology but the densities of their flowers fluctuated, resulting in a seasonal partitioning of flower visitation. The differences in corolla symmetry and mainly the temporal partitioning among pollinators throughout the day and the flowering season proved to be important factors in maintaining the synchronopatry of V. longifolia and V. luteola.     

Specialized pollination by fungus gnats in the introduced population of <Emphasis Type="Italic">Aspidistra elatior</Emphasis>

The monocot genus Aspidistra comprises rhizomatous perennials that are distributed in tropical to warm temperate regions of Asia. Little is known about the pollinators of almost all the species, probably due to the inconspicuous nature of Aspidistra flowers. Nevertheless, the unusual floral morphology suggests biotic pollination, since pollen grains are hidden under each flower’s stigma. Aspidistra elatior has been suspected to have a very peculiar pollination ecology. So far, pollination by mollusks, crustaceans, or collembolans has been suspected. However, a recent study showed that A. elatior is mainly pollinated by species of fungus gnats in Kuroshima Island, southern Japan, which is its natural habitat. Here, we investigated the pollination ecology of A. elatior in Shiga Prefecture, central Japan, which is the introduced population, to reveal whether fungus gnats are also the main pollinator in the introduced population. Our study confirmed fungus gnats pollination in the investigated pollination. Furthermore, the main pollinators (i.e., Cordyla sixi and Bradysia sp.) are the same in both Kuroshima and Shiga Prefecture. Therefore, A. elatior mainly depends on a narrow taxonomic group of fungus gnats for pollination. In contrast, we failed to document any terrestrial amphipods visiting the A. elatior flowers, in spite of a relatively high fruit set in natural conditions. This fact will refute the amphipod pollination hypothesis proposed by previous studies. We consider that A. elatior is pollinated by fungus gnats through fungal mimicry, due to its superficial similarity to mushroom fruiting bodies and strong, musky floral scent.     

Ants as floral visitors of <Emphasis Type="Italic">Blutaparon portulacoides</Emphasis> (A. St-Hil.) Mears (Amaranthaceae): an ant pollination system in the Atlantic Rainforest

Ant pollination is a debated topic that requires more attention in order to clarify the role of ants as potential pollinators. Although many authors consider ants as mere nectar robbers, there are studies proving that ants may act as pollinators and that some plants even have flower traits acting as ant attractors. In this study, we evaluated the role of the ants in pollination of Blutaparon portulacoides inflorescences. This plant species has most of the traits favorable for ant pollination, such as short and aggregated inflorescences, and synchronized blooming as well as growing in an environment where ant pollination is likely to occur. Our results show that ants are the most abundant visitors throughout the day and that there is no effect of ant integument on pollen germination. Furthermore, the flower visitor exclusion experiment showed that ants have a role in the pollination of B. portulacoides by promoting seed formation. Ants can have an important part in the pollination of B. portulacoides in a scenario where winged insects are absent or scarce.     

Role of insect vectors in epidemiology and invasion risk of <Emphasis Type="Italic">Fusarium circinatum</Emphasis>, and risk assessment of biological control of invasive <Emphasis Type="Italic">Pinus contorta</Emphasis>

Pitch canker, caused by the pathogen Fusarium circinatum, is a serious disease of pines, Pinus species. It is a threat to natural and planted pine forests, and to date it has invaded countries across five continents. Pine-feeding insects can play a key role in the epidemiology of the disease, as wounding agents allowing pathogen access or as vectors transmitting the pathogen from infected to healthy trees. We reviewed the role of insects in the epidemiology of pitch canker worldwide and assessed which insects are present in New Zealand that may act as wounding agents or vectors to determine whether pathogen invasion could adversely affect Pinus radiata plantation forests and urban trees. We also evaluated whether cone or seed insects of pines could be introduced as biological control agents of invasive Pinus contorta and how this may affect the impact of a potential F. circinatum invasion. As there are no native pines or other Pinaceae in New Zealand, there are only a few pine insects, mainly accidental introductions. None of the insects recorded on pines in New Zealand is likely to be a vector, suggesting low disease risk. Of six potentially suitable biocontrol candidates, the European pine cone weevil Pissodes validirostris is the most promising regarding host specificity and impact on seed production, but there is uncertainty about its ability to act as a vector of F. circinatum. Our methodology to review and evaluate the vector potential of pine associates can be used as a generic framework to assess the potential impacts of F. circinatum invasion.     

Specific features of pollination in the Manchurian birthwort, <Emphasis Type="Italic">Aristolochia manshuriensis</Emphasis>

An analysis of pollination system in Aristolochia manshuriensis has shown that flower structure in this species is strictly adapted to cross-pollination, but the possibility of an autogamous or geitonogamous type of self-pollination with the involvement of insects is not excluded. The flowers of A. manshuriensis are most frequently visited by flies of the family Anthomyiidae, which markedly contribute to their pollination. Males account for 65% of pollinator insects collected from the flowers.