Pollen Vectors Research Articles

Scented at day and night: diel variation in the floral scent chemistry of the threatened tree Amburana cearensis (Leguminosae) and effects of this variation on its pollinators

The reproductive success of most angiosperms depends on pollinators. A combination of floral traits, including olfactory cues, are involved in attracting these animals. The emission and chemical composition of floral volatile organic compounds (VOCs) is often associated with the sensory preferences of the most frequent floral visitors. However, the relationship between VOCs and nocturnal and diurnal pollinators is poorly known in tropical dry forests. Our study describes the dynamics of floral scent chemistry throughout the anthesis of Amburana cearensis (Leguminosae) and its association with floral visitors in the Caatinga dry forest, one of the largest expanses of seasonally dry tropical forest (SDTF) in the world. The species is a threatened tree with high socioeconomic importance in the Caatinga and other SDTFs of South America (exploited for timber and medicinal uses). Its flowers emit an intense, pleasant and sweet fragrance throughout anthesis, starting at ∼16:00 h and ending at ∼15:00 h of the following day (lasting 23 h). We used dynamic headspace sampling and gas chromatography coupled with mass spectrometry (GC-MS) to collect and analyze the floral scent within a natural population. The fragrance of A. cearensis was characterized by the dominant presence of monoterpenes, especially linalool and (Z)-linalool oxide (furanoid) and (Z)-linalool oxide (pyranoid), as well as (E,E)-α-farnesene and an aromatic benzenoid, benzyl alcohol. The relative proportions of floral VOCs emitted by A. cearensis changed during anthesis, with a marked presence of linalool in daytime samples (day: 45% / night: 27%) and furanoid (Z)-linalool oxide at night (day: 12% / night: 29%). The dominance of benzyl alcohol, linalool and its oxides in the floral scent of A. cearensis is possibly related to the attraction of nocturnal and diurnal Lepidoptera as pollen vectors. Indeed, we observed six species of butterflies and seven species of moths pollinating the flowers of A. cearensis in 41 h of observations. However, other terpenoids in the fragrant blend possibly contribute to the attraction of additional diurnal floral visitors, including bees, which are also effective pollinators. The continuous scent production throughout anthesis, and the changes in floral scent with a peak of linalool production during the day, may be related to the wide spectrum of pollinators of A. cearensis. This association between floral visitors and dynamics of VOCs presentation may therefore increase the reproductive success of the species, which only blooms every two years and is strictly self-incompatible.

By land and by tree: Pollinator taxa diversity of terrestrial and epiphytic orchids

There are approximately 30,000 species in the family Orchidaceae, with some species growing terrestrially and others growing as epiphytes. Though the pollination biology of many of these species is not well known, there has been a diversity of taxa recorded as orchid pollinators. Insects, birds, and even a record of a mammal species have been documented as successful pollinators, while some orchids are able to reproduce without the use of a pollen vector. The goal of this review is to provide an overview of orchid pollination tactics, with references to more specific studies of each, and to analyze a large subset of publications to determine differences in pollinator taxa and specificity between epiphytic and terrestrial orchid genera. This review examines pollination data from over 400 orchid species, including 74 epiphytic and 83 terrestrial orchid genera. Two pollinator taxa, Coleoptera and Hymenoptera (Class: Insecta), were found to pollinate significantly more terrestrial than epiphytic orchid genera, while other taxa showed no significant differences. Hymenoptera were the dominant taxa of pollinator in regards to the overall number of species recorded; however, based on species interaction webs that were built, the Lepidoptera (Class: Insecta) have stronger interactions with the orchid species they pollinate, suggesting a more specific relationship between the two.

Native bees with floral sonication behaviour can achieve high‐performance pollination of highbush blueberry in Chile

Abstract Blueberry is one of the most relevant buzz‐pollinated crops worldwide and Chile is the most important global producer of fresh blueberries during wintertime in the Northern Hemisphere. Thousands of exotic Bombus terrestris are imported from Europe to pollinate blueberries. However, no study has investigated the performance of the native Chilean fauna to pollinate blueberry or other crops. Therefore, we aimed to compare the performance of native Chilean floral visitors with managed visitors to pollinate highbush blueberry. Per‐visit pollination performance (stigmatic pollen deposition) and floral visitation were measured and the presence of sonication behaviour of flower visitors was evaluated for five cultivars in two blueberry orchards located in southern Chile. Floral visitors showed a preference for one or more blueberry cultivars, instead of visiting all cultivars equally. Floral visits with sonication deposited more conspecific pollen on stigmas than visits without sonication. Some native sonicating bees (Cadeguala and Bombus), especially Cadeguala occidentalis, were efficient pollen vectors of blueberry and better pollinators than honeybees (5.8 times more pollen transferred) similar to that of the managed bee B. terrestris. The results indicate that some Chilean native bee species, especially those with sonication behaviour, can provide pollination service to highbush blueberry crops.

Floral and pollination biology of the critically endangered insular orchid Calanthe amamiana: Implications for in situ conservation

AbstractCalanthe amamiana is a terrestrial orchid that thrives on the shady forest floors of broad‐leaved forests on Amami Island, central Ryukyus, Japan. Here, I report on the floral and pollination biology of this critically endangered orchid based on a 7‐year study conducted in the species' natural habitats. As the nectarless flowers are probably self‐compatible but are unable to autonomously self‐pollinate, they need to attract pollen vectors by deceit for pollination. To advertise themselves, the flowering inflorescences, which comprise a few to dozens of flowers, use whitish floral colors that are comparatively conspicuous against the shaded background. The exclusive pollinator was the long‐horned bee Eucera okinawae, which nests in soils of the forest floor, although bee abundance varied considerably among study years. Natural fruit‐set ratios were generally low but showed interannual variation. The annual fruit‐set ratios were positively correlated with annual bee abundance, thereby suggesting that under natural conditions, the orchid is pollinator‐limited. Given that C. amamiana is dependent exclusively on E. okinawae for pollination and is also probably pollinator‐limited, conservation plans for this orchid should take into consideration the welfare of long‐horned bees. In particular, as nectariferous flowers were unavailable within broad‐leaved forests, to satisfy the foraging requirements of long‐horned bees, conservation managers should be cognizant of conservation values of flowering plants distributed in sun‐lit sites near orchid habitats, and manage those in an appropriate manner.

Self-compatibility provides little reproductive assurance in the summer-flowering Aloe reitzii var. reitzii

Floral adaptations, notably floral design and display, enable plants to govern their mating opportunities through pollinator attraction and pollen dispersal. However, large floral displays, together with multiple simultaneously open flowers in an hermaphroditic plant, increase the potential for geitonogamous self-pollination. Many angiosperms have evolved self-incompatibility that prevents self-fertilization, instead requiring outcrossing by pollen vectors for successful seed set. We investigated the reliance of the summer-flowering Aloe reitzii var. reitzii on pollinators for reproduction and by using controlled hand-pollination experiments to determine whether Aloe reitzii var. reitzii is self-compatible. Contrary to most aloes, Aloe reitzii var. reitzii is shown here to be partially self-compatible, but reliant on pollinators to transfer pollen between flowers within the same raceme or plant, as well as to other plants. Aloe reitzii var. reitzii appears incapable of autonomous self-pollination and pollinator-mediated geitonogamy causes reduced fecundity in Aloe reitzii var. reitzii. However, hand-selfed treatments produced viable seeds capable of germinating, suggesting that the partial self-compatibility in Aloe reitzii var. reitzii does provide some reproductive advantage and may have evolved due to its restricted distribution and increasing population fragmentation – possibly due to anthropogenic change.

In situ and Ex situ Investigations on Breeding Systems and Pollination of Sideritis Scardica Griseb. (Lamiaceae) in Bulgaria

Sideritis scardica is a short living perennial herb. This Balkan endemic grows in the higher parts of the mountains of Bulgaria, Albania, Greece, and Republic of North Macedonia. It is an endangered species and medicinally valuable plant. S. scardica has been successfully cultivated lately in Bulgaria and propagated by seed. This study presents preliminary in situ and ex situ data on the factors that control the seed production of S. scardica. Investigations were conducted in six study sites (three in situ and two ex situ) in the Rhodopes and one ex situ study site in the foothills of Pirin Mt in 2008 and 2019. The field experiments with enclosed flowers revealed that spontaneous self-pollination does not occur and insect pollen vectors are necessary. The pollinators of S. scardica were polylectic insects such as bumblebees (both in situ and ex situ) and honeybees (only on the big ex situ cultivated fields). Flowers were visited mostly for nectar as a reward and the pollen baskets were filled mainly by the pollen adhered on the pollinators’ body. The protection of wild populations of this plant species as well as its successful cultivation depends on the protection of its pollinators.

A Continuum of Conspicuousness, Floral Signals, and Pollination Systems in Rhynchospora (Cyperaceae): Evidence of Ambophily and Entomophily in a Mostly Anemophilous Family

Floral colors and odors are evolutionary strategies used by plants to attract pollinating animals and may be absent in mostly anemophilous groups, such as Cyperaceae. However, considering that insects are floral visitors of some Rhynchospora Vahl species, the objective of this study was to characterize the floral traits and pollination systems within this genus. We analyzed 16 Rhynchospora species with regard to flower morphology, colors of floral structures, floral scents, pollen vectors, and pollination systems. We verified factors that can favor abiotic or biotic pollination in a continuum of floral traits in Rhynchospora. The flower morphology of R. dissitispicula T. Koyama, with inconspicuous brown spikelets in open panicles, is interpreted as a complete adaptation to anemophily. Conspicuous floral traits in Rhynchospora were distinguished from the background by bees. Some species also emit floral volatiles, and we made the first record of floral scent chemistry within the genus. Most of the compounds emitted by these species are known as attractants to many floral-visiting insects. Bees, beetles, and flies visited species with conspicuous floral traits and contributed to fruit set. The investigated floral traits form a continuum across the different pollination systems in Rhynchospora, from anemophilous to ambophilous and then to entomophilous representatives.

The pollination of the gynomonoecious Bdallophytum oxylepis (Cytinaceae, Malvales)

AbstractBdallophytum oxylepis is a rare and endemic species belonging to the Cytinaceae family, a root holoparasitic plant in which most resources are allocated to attracting pollinators. This species is gynomonoecious with intraindividual variation in flower size and sex. Moreover, the flowers exhibit sapromyophilous traits, as do other species of Bdallophytum. Firstly, this study aimed to determine whether all floral morphs can form seeds and be pollen donors (in the case of bisexual flowers). Secondly, as this species has floral traits hypothesized to adapt to particular types of pollen vectors (carrion flies), we also studied the pollination of B. oxylepis to confirm whether the syndromes correspond to what occurs in nature. Through pollination treatments, we determined that all floral morphs are functional. By monitoring the inflorescences, we found that pollination is specialized in the studied population. Stingless bees performed pollination, as they have a high visitation rate, frequency, and constancy, and they are unique visitors that deposit pollen on the stigmas. Thus, they appear to be effective pollinators rather than carrion flies, as predicted by the syndrome. As shown here, animal–plant interaction studies can help establish a basis for conserving rare species such as holoparasites. Moreover, knowledge about the reproductive aspects of B. oxylepis reveals essential clues about its life cycle and role in maintaining native pollinators with economic and cultural value, such as stingless bees.

Coleopteran Pollinators of Annonaceae in the Brazilian Cerrado—A Review

The evolutionary trajectories of insects and angiosperms appear to be intimately interconnected. Increases in the diversity of phytophagous beetles and angiosperms co-occur in the Mesozoic fossil record, and there is fossil evidence of pollinivory and pollination by insects, both in flowering plants and in gymnosperms. The oldest records of angiosperm pollination indicate flies as pollen vectors. A basal group of angiosperms, the order Magnoliales, has retained plesiomorphic characters such as dozens of pistils and stamens spiraling around the receptacle. In a family of this order, Annonaceae, over 90% of species are pollinated by beetles. In many Annonaceae species, flowers display wide spaces, referred to as floral chambers, where beetles can find shelter from weather conditions and predators, food in the form of pollen and tissues, and a mating site. Two basic types of floral chambers can be distinguished: small chambers visited by small beetles (Nitidulidae, Staphylinidae, Chrysomelidae, and Curculionidae) with diurnal and/or nocturnal activity and large and thermogenic floral chambers visited by beetles of the tribe Cyclocephalini (Scarabaeoidea, Melolonthidae). In the latter case, the heat that the flowers produce may serve as a resource for the beetles that visit them, resulting in smaller endothermy costs for the scarabs. This study reviewed the literature including PhD and MSc theses on cantharophilous Annonaceae in the Cerrado. In this biome, both types of associations are found, although cantharophilous Annonaceae represent a small portion of the plant species (<5%). Cantharophilous Annonaceae in the Cerrado share attributes according to the beetles that pollinate them: species pollinated by small beetles, for instance, may flower throughout the year, whereas Annonaceae pollinated by Cyclocephalini normally flower in the beginning of the rainy season (October/November), in synchrony with the phenological patterns of their pollinators. Cantharophilous Annonaceae flowers, regardless of their size, tend to have light colors and sweet and fruity odors. In addition to the lack of studies on the attraction of beetles by these floral characters, the taxonomic composition of the beetles that pollinate Annonaceae in the Cerrado is poorly known. This review attempts to discuss, in light of what has already been published, potential fields of investigation concerning pollinating beetles’ behavior and evolution.

Occurrence and Prevention of Delayed Autonomous Selfing in Salvia umbratica (Lamiaceae).

Delayed autonomous selfing (DAS) provides reproductive assurance under conditions of pollinator and/or pollen-limitation. Few plant species have been investigated to determine if DAS is terminated when a flower is sufficiently pollinated by a pollen vector, thereby saving plant resources for other purposes. We examined this possibility in bumblebee-pollinated Salvia umbratica. We first showed that DAS resulting in high fruit set (100%) and seed set (>80%) per flower occurred in the absence of insect pollinators by means of style recurvature and was completed in 94% of flowers 72 h after they opened. In contrast, in flowers pollinated immediately after opening, DAS was prevented by corollas dropping away before styles recurve toward the upper thecae. We next showed that hand-pollination of flowers immediately after they opened resulted in high fruit set (100%) and seed set (>80%) when 5–10 pollen grains or more were deposited on their stigmas, whereas fruit set and seed set were reduced to 45.00 and 22.50%, respectively, when pollen loads were reduced to 1–3 pollen grains. Finally, we showed that on average single pollinator visits deposited 26 pollen grains on stigmas of flowers that had just opened, which is more than enough to ensure high fruit and seed set. Our results indicate that flower longevity is highly correlated with the pollinator environment and female fitness of S. umbratica, with extended flower longevity allowing DAS to occur being advantageous when pollinators are absent, while reduced floral longevity and prevention of DAS being favored when flowers are pollinated by pollinators. Thus, flower longevity in S. umbratica varies so as to optimize reproductive output and resource efforts, and is dependent on the availability and effectiveness of pollinators to pollinate flowers.

Three options are better than two: compensatory nature of different pollination modes in <i>Salix caprea</i> L.

Mixed pollination systems have been reported for many angiosperms. Here, we report on a dioecious willow, Salix caprea L., which employs three pollination modes, namely pollination by wind, nocturnal moths, and diurnal bees. In four field populations of S. caprea in Germany, we addressed the following questions: (a) How are the pollination modes affected by local mate availability? (b) What is the contribution of each pollination mode to seed set? (c) How does flower opening time affect pollination? We compared seed set among seven pollination treatments (wind pollination, diurnal pollination, nocturnal pollination, natural pollination, apomictic reproduction, daytime/night-time artificial pollination). Pollen limitation was observed across populations. On the other hand, limitations in mate availability affected the pollination modes differently. Insect pollination outperformed wind pollination in situations where nearby males were few or all positioned in the same direction from the females. The contribution of nocturnal moths was lower than that of the other pollen vectors. However, moth pollination worked complementarily with bee pollination in compensating for the lack of wind pollination. Furthermore, we found that the onset of flower anthesis peaked at sunset, and that cold night temperatures had no negative effect on seed set or pollen viability. Thus, nocturnal anthesis and prior pollination by moths may minimize male fitness loss due to pollen collection and grooming by bees. We suggest that S. caprea maximizes its fitness by combining multiple pollination modes that work in different environmental conditions, while optimizing the anthesis so that more pollen would be delivered to stigmas.

Floral attraction and flower visitors of a subcanopy, tropical rainforest tree, Fontainea picrosperma.

Flowering plants in tropical rainforests rely heavily on pollen vectors for successful reproduction. Research into pollination systems in tropical rainforests is dominated by canopy species, while subcanopy plant–pollinator interactions remain under‐represented. The microclimate beneath the rainforest canopy is characterized by low light levels and is markedly different from the canopy environment that receives more light energy.We studied the floral attractants and floral visitors of a dioecious, subcanopy tree, Fontainea picrosperma (Euphorbiaceae), in the Wet Tropics bioregion of northern Queensland, Australia.We found that wind pollination is rare and male and female flowers do not produce nectar. Female flowers are likely pollinated due to their perceptual similarity to pollen‐offering male flowers. Female flowers had the same scent profile as male flowers, and floral scent was an important floral attractant that acted to regulate pollinator behavior. The two most abundant scent compounds present in the floral bouquet were benzyl alcohol and 4‐oxoisophorone. These compounds are ubiquitous in nature and are known to attract a wide variety of insects. Both day‐time and night‐time pollinators contributed to successful pollen deposition on the stigma, and diurnal flower visitors were identified from several orders of insects including beetles, flies, predatory wasps, and thrips. Fontainea picrosperma is therefore likely to be pollinated by a diverse array of small insects.Synthesis. Our data indicate that F. picrosperma has a generalist, entomophilous pollination syndrome. The rainforest subcanopy is a distinctive environment characterized by low light levels, low or turbulent wind speeds, and relatively high humidity. Female flowers of F. picrosperma exhibit cost‐saving strategies by not producing nectar and mimicking the smell of reward‐offering male flowers. Insects opportunistically forage on or inhabit flowers, and pollination occurs from a pool of small insects with low energy requirements that are found beneath the rainforest canopy.

The impact of global warming on the niches and pollinator availability of sexually deceptive orchid with a single pollen vector

Orchidaceae are among the most endangered plants in the world. Considering the sensitive nature of pollinator-plant relationship the most vulnerable are species which are dependent on a single pollen vector. In this paper the future distribution of suitable niches of Australian sexually deceptive orchid Leporella fimbriata and its pollinator (Myrmecia urens) was estimated using three machine learning algorithms. While the potential range of fringed hare orchid depending on modelling method will be larger or slightly reduced than currently observed, the ant will face significant loss of suitable niches. As a result of global warming the overlap of orchid and its only pollen vector will most probably decrease. The unavailability of pollen vector will lead to decreased reproductive success and as a result it will be a great threat for L. fimbriata existence.

The pollination seesaw of Rhynchospora cephalotes (L.) Vahl (Cyperaceae): Influence of plant location on the role of wind and insects as pollen vectors

AbstractAmbophily (wind and insect pollination) has been reported for some genera of the typically wind‐pollinated family Cyperaceae, including the genus Rhynchospora. The significance of wind and insect pollination can vary, depending on local microclimatic conditions. Rhynchospora cephalotes is an ambophilous species that can grow under different environmental conditions, either along forest edges or inside forest fragments. This study, therefore, tests the hypothesis that (a) there is greater contribution by wind than insects to fruit set of the individuals at the forest edge and (b) there is greater contribution by insects than wind to fruit set of the individuals inside the forest. Field work was carried out in a fragment of Atlantic Forest in northeastern Brazil. We quantified the number of visits by insects, wind velocity and the reproductive success (fruit set) of R. cephalotes provided by wind and insects through exclusion experiments performed at the edge of and inside the forest. We observed a greater number of visits per day by pollinating bees to individuals inside the forest (36.83 ± 7.46) than to individuals at the edge (16.66 ± 6.53). The wind speed was significantly higher at the edge (1.71 ± 0.46 m/s) than inside the forest (0.97 ± 0.18 m/s). Bees and wind are both pollen vectors of R. cephalotes, but bees were the pollen vector that contributed most to fruit set (63.3%) for individuals inside the forest, whereas wind was the primary vector for individuals at the forest edge (76.6%). This seesaw in importance of each pollen vector in the two different environments guarantees high fruit set in R. cephalotes under different microclimatic conditions.

A case study of insect visitors and pollen vectors in sponge gourd (Luffa cylindrica (Linn.)) during summer and rainy seasons in India

Insect crop visitations do not necessarily always translate to transfer or carriage of pollen. To determine the potential of the various insects visiting summer and rainy seasons sponge gourd (Luffa cylindrica (Linn.)) flowers to facilitate the pollen transfer, the present study examines the diversity of visiting insects to sponge gourd seed crops in relation to the time of day and season, diversity and abundance to its flowers, fruits and seed yield. These visiting insects taxonomically belonged to 8 different insect orders viz. Coleoptera, Diptera, Hymenoptera, Hemiptera, Neuroptera, Lepidoptera, Odonata and Orthoptera/Dictyoptera. Rainy season sponge gourd crops had higher numbers of insect visitors and higher diversity (0.80 of Simpson’s Diversity Index and 1.71 of Shannon–Weaver Index of diversity as compared to summer season crop (0.72 and 1.51, respectively). The summer crop had the highest number of visiting insects belonged to the order Coleoptera followed by Hemiptera and Hymenoptera and their reciprocal form of Berger Parker’s dominance indices were 2.21, 5.05 and 6.17, respectively. In summer crop, honeybees were the main pollinators comprising 57.69% of total pollinators in sponge gourds. All the four honeybee species viz., Apis cerana indica, A. dorsata, A. florea and A. mellifera were found to visit in sponge gourd. However, the dominant species was A. florea with 39% of total honeybee share. In rainy season crop, in contrary, honeybees comprised only 16.32% share on total visiting pollinators in sponge gourd. Rice skipper, Pelopidas mathias (46.84% share) was found almost thorough out the day with higher visitation during evening hours. Other pollinators were stingless bees (11.58% share), butterflies and moths. Consequently, we suggest optimizing pollinators’ management including honeybees and thereby improving the attraction of sponge gourd lines to these pollinators to improve pollination rates for sponge gourd seed crops.

Pollination ecology and breeding systems of Cypripedium kentuckiense (Orchidaceae) in Tennessee1

The orchid Cypripedium kentuckiense is listed as imperiled in Tennessee and Oklahoma and critically imperiled in seven other states. We followed individuals' vegetative and floral traits over two seasons. Patterns of floral senescence were found to vary over two seasons and might be related to April temperatures when buds develop. Mechanical self-pollination was uncommon but perhaps “leaky.” Frequencies of insect-mediated pollination were surprisingly high (62%) for a Cypripedium species with large flowers but conversion of flowers into fruit was low (7% and 14%), suggesting that cryptic factors lower reproductive success, not inadequate pollinator visits. Hand-pollinations suggest flowers are self-compatible. As in other Cypripedium species, floral architecture relates to pollinator dimensions but at this site, only two bee species, Anthophora abrupta and A. bomboides, were primary pollinators. Male A. abrupta were common visitors although male bees are uncommon pollen vectors of Cypripedium species. For the first time, exit patterns of bees inside Cypripedium flowers were recorded based on bee species and gender. This behavior varied and was somewhat atypical of previous studies on other bee-pollinated species in the clade and genus. Specifically, Anthophora species within labella chewed on the epidermis lingering within the interior and exit canals. Consequently, C. kentuckiense might not be a trap.

Co-pollination, constancy, and efficiency over time: small beetles and the reproductive success of Acrocomia aculeata (Arecaceae) in the Colombian Orinoquia

ABSTRACT Acrocomia aculeata is under accelerated domestication due to the high yield and quality of the oils obtained from the fruits. Key details about its reproduction and fruit production, notably its dependence on cross-pollination, have not been thoroughly assessed. In the course of three successive reproductive seasons, we investigated the phenology, floral biology, pollination ecology, and reproductive efficiency of a natural population of A. aculeata in the department of Casanare, Colombian Orinoquia. We determined the effective pollinators among floral visitors based on their abundance, pollen carrying capacity, and constancy in association with receptive female-phase inflorescences. The studied population of A. aculeata exhibited a seasonal reproductive cycle, producing inflorescences during the drier months of December to April (peaking in March) and mature fruits from October to March. Each individual produces six to ten protogynous inflorescences, with a female phase that lasts ca. 12 h and a male phase extending for four to five days. A total of 48 insect species were observed in association with A. aculeata, averaging over 3500 visitors per anthetic female-phase inflorescence. Flower weevils (Andranthobius spp.; Derelomini) and small sap beetles (Mystrops sp.; Mystropini) were the most abundant visiting species and main pollinators, accounting for 90–95% of effective pollination services. Their high efficiency as pollen vectors was evident, as fructification rates reached on average 65.5% during the three years of study. Our findings support the assumption that co-pollination in A. aculeata evolved as a specialized strategy to maintain a high and temporally stable reproductive efficiency over time.

Significant habitat loss of the black vanilla orchid (Nigritella nigra s.l., Orchidaceae) and shifts in its pollinators availability as results of global warming

The black vanilla orchid (Nigritella nigra s.l.) is a perennial plant found in the main European mountain ranges. It occurs in large numbers in the Alps, but it has become a rare and endangered species in Scandinavia. Two subspecies of N. nigra s.l are recognized by most authors – the nominal subspecies which is restricted in its distribution to Scandinavia and N. nigra subsp. austriaca which is found in the alpine region. Some taxonomists postulated that these two taxa should be considered as separated species. The N. nigra s.l. is pollinated mostly by Lepidoptera. As a mainly montane species it is especially fragile to global warming, however, some previously published reports indicated that the climate changes will not significantly affect northern populations of this species. The aim of this study was to evaluate the differences in the climatic niche preferences between Scandinavian and central European populations of the black vanilla orchid and to estimate the impact of global warming on the distribution of this species using (ENM). Additionally, the predicted future location and extent of suitable climatic niches of insects pollinating studied orchid was modeled in order to estimate the availability of pollinators for this montane plant. This approach was applied as the persistence of an orchid population depends on pollination and subsequent seed production. Our analyses showed that the northern and southern populations differ in bioclimatic preferences and geographical distribution of these orchids together with variations in their chromosomes number and morphological discrepancies, suggest that N. nigra in not homogenous taxon as postulated by some authors and this approach should be also applied in assessing conservation priorities in Europe. Both, northern and southern population of N. nigra, will face significant habitat loss as a result of the global warming. In the best case scenario (rcp2.6) only 31.7% and 60.5% of the currently suitable niches will be still available for N. nigra respectively. The most damaging rcp8.5 scenario will cause the extreme decline of the coverage of orchid and just 2.3% of the habitats will be still suitable for N. nigra in the North and 18% for N. nigra in the South. Within the future potential range of N. nigra and N. nigra subsp. austriaca some pollinators will be still available for orchids, mostly for the latter taxon. Considering that the flowering time of the orchid seems to overlap with the activity of pollinators for the last 70 years we not expect significant desynchronization of these events which could prevent pollen transfer. Noteworthy as the Scandinavian populations N. nigra is characterized by lower genetic diversity than in the alpine region of central Europe, species seems to be more endangered in the North (Moen and Øien, 2002) and the future loss of habitats predicted in our study together with limited availability of pollinators can led to loss of the unique gene pool of this orchid. In our opinion this fact should be considered in the establishment of nature protection projects and the conservation efforts should focus on areas which in the future will be still suitable for occurrence of this species and its pollen vectors.

Disentangling the ecological basis of floral trait variation in NeotropicalPiperspecies

AbstractIn generalist pollination systems, it has been assumed that pollinators play a minor role in the diversification of floral traits, but recent studies have pointed to a different scenario. Although pollination in Piper is considered generalist, there are flower and inflorescence variations among subclades that may be associated with different pollinator functional groups. Based on this, we aimed to test whether pollinators influenced the evolution of floral traits in a clade of generalist plants, by studying 17 co-occurring Piper spp. Sixteen species were insect-pollinated (46 species: bees, beetles and flies). We found no evidence of anemophily. Eight species were dependent on pollen vectors for sexual reproduction, but no correlation between floral and pollinator traits was recorded. None of the floral traits presented phylogenetic signal, and the evolution of these traits was not correlated. Nine species were independent of pollen vectors for sexual reproduction. We did not find any evidence of pollinator-driven floral diversification of Piper spp.; we suggest a possible role of abiotic factors as agents of selection on floral diversification. As self-pollination seems to be a common feature in the genus, the flexibility of mating systems could be another important factor related to the maintenance of floral phenotypic variation.

Scent chemistry and pollinators in the holoparasitic plant Cynomorium songaricum (Cynomoriaceae).

Holoparasitic plants are interesting heterotrophic angiosperms. However, carrion- or faeces-mimicking is rarely described for such plants. There is no information on the pollination biology of Cynomoriaceae, despite the fact that these plants are rare and vulnerable. This is the first study to reveal pollination in a member of this family, Cynomorium songaricum, a root holoparasite with a distinctive and putrid floral odour. From 2016 to 2018, we studied the floral volatiles, floral visitors and pollinators, behavioural responses of visitors to floral volatiles, breeding system, flowering phenology and floral biology of two wild populations of C. songaricum in Alxa, Inner Mongolia, China. A total of 42 volatiles were identified in inflorescences of C. songaricum. Among these volatiles are compounds known as typical carrion scents, such as p-cresol, indole, dimethyl disulphide and 1-octen-3-ol. C. songaricum is pollinated by various Diptera, such as Musca domestica, M. stabulans (Muscidae), Delia setigera, D. platura (Anthomyiidae), Lucilia sericata, L. caesar (Calliphoridae), Wohlfahrtia indigens, Sarcophaga noverca, S. crassipalpis and Sarcophila meridionalis (Sarcophagidae). The inflorescence scent of C. songaricum attracted these pollinators. The plants significantly benefit from insect pollination, although wind can be a pollen vector in the absence of pollinators. C. songaricum is a cross-pollinated, self-incompatible plant. Our findings suggest that C. songaricum releases malodorous volatiles to attract Diptera to achieve pollination. This new example lays the foundation for further comparative studies in other members of this plant group and contributes to a better understanding of fly-pollinated, carrion mimicking plants.