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opencc-zeroNov 2021View details →

Effects of different types of low-intensity management on plant-pollinator interactions in Estonian grasslands

In the face of global pollinator decline, extensively-managed grasslands play an important role in supporting stable pollinator communities. However, different types of extensive management may promote particular plant species and thus particular functional traits. As the functional traits of flowering plant species (e.g. flower size and shape) in a habitat determine the identity and frequency of pollinator visitors, they can also influence the structures of plant-pollinator interaction networks. The aim of this study was to examine how the type of low-intensity traditional management influences plant and pollinator composition, the structure of plant-pollinator interactions, and their mediation by floral and insect functional traits. Specifically, we compared mown wooded meadows to grazed alvar pastures in western Estonia. We found that both management types fostered equal diversity of plants and pollinators, and overlapping, though still distinct, plant and pollinator compositions. Wooded meadows had significantly higher connectance and specialisation, while alvar pastures achieved higher Shannon diversity at a standardised sampling of interactions. Pollinators with small body sizes and short proboscis lengths were more specialised in their preference for particular plant species and the specialisation of individual pollinators was higher in alvar pastures than in wooded meadows. All in all, the two management types promoted diverse plant and pollinator communities, which enabled the development of equally even and nested pollination networks. The same generalist plants and pollinators were important for the pollination networks of both wooded meadows and alvar pastures; however, they were complemented by management-specific species, which accounted for differences in network structure. Therefore, the implementation of both management types in the same landscape helps to maintain high species and interaction diversity.

Figure 3 in Uvariopsis dicaprio (Annonaceae) a new tree species with notes on its pollination biology, and the Critically Endangered narrowly endemic plant species of the Ebo Forest, Cameroon

Figure 3 Uvariopsis dicaprio. (A) habit, cauliflorous inflorescences on trunk; (B) leafy branch, one season's growth; (C) inflorescence, showing pedicel articulations, bracts and bracteoles; (D) flower, with one petal removed to show the staminal dome; (E) detail of sparse hairs on abaxial petal surface; (F) stamen, different views; (G) junction of base of leaf with stem, showing dome-like axillary bud. All drawn from MacKinnon 51 (K) by MEG GRIFFITHS. Full-size DOI: 10.7717/peerj.12614/fig-3

Figure 4 in Uvariopsis dicaprio (Annonaceae) a new tree species with notes on its pollination biology, and the Critically Endangered narrowly endemic plant species of the Ebo Forest, Cameroon

Figure 4 Global distribution of Uvariopsis dicaprio, together with U. korupensis and U. submontana. Full-size DOI: 10.7717/peerj.12614/fig-4

Figure 1 in Uvariopsis dicaprio (Annonaceae) a new tree species with notes on its pollination biology, and the Critically Endangered narrowly endemic plant species of the Ebo Forest, Cameroon

Figure 1 Uvariopsis dicaprio. Cauliflorous inflorescences on trunk. Photo Lorna MacKinnon. Full-size DOI: 10.7717/peerj.12614/fig-1

Figure 2 in Uvariopsis dicaprio (Annonaceae) a new tree species with notes on its pollination biology, and the Critically Endangered narrowly endemic plant species of the Ebo Forest, Cameroon

Figure 2 Uvariopsis dicaprio. Trunk apex with cauliflorous flowers and canopy. Photo Lorna MacKinnon. Full-size DOI: 10.7717/peerj.12614/fig-2

opencc-zeroFeb 2022View details →

Genome-wide sequence data show no evidence of hybridization and introgression among pollinator wasps associated with a community of Panamanian strangler figs

The specificity of pollinator host choice influences opportunities for reproductive isolation in their host plants. Similarly, host plants can influence opportunities for reproductive isolation in their pollinators. For example, in the fig and fig wasp mutualism, offspring of fig pollinator wasps mate inside the inflorescence that the mothers pollinate. Although often host specific, multiple fig pollinator species are sometimes associated with the same fig species, potentially enabling hybridization between wasp species. Here we study the 19 pollinator species (Pegoscapus spp.) associated with an entire community of 16 Panamanian strangler fig species (Ficus subgenus Urostigma, section Americanae) to determine whether the previously documented history of pollinator host switching and current host sharing predicts genetic admixture among the pollinator species, as has been observed in their host figs. Specifically, we use genome-wide ultraconserved element (UCE) loci to estimate phylogenetic relationships and test for hybridization and introgression among the pollinator species. In all cases, we recover well-delimited pollinator species that contain high interspecific divergence. Even among pairs of pollinator species that currently reproduce within syconia of shared host fig species, we found no evidence of hybridization or introgression. This is in contrast to their host figs, where hybridization and introgression have been detected within this community, and more generally, within figs worldwide. Consistent with general patterns recovered among other obligate pollination mutualisms (e.g., yucca moths and yuccas), our results suggest that while hybridization and introgression are processes operating within the host plants, these processes are relatively unimportant within their associated insect pollinators.

opencc-by-4.0Mar 2022View details →

Datasets from Ganuza et al. 2022: Interactive effects of climate and land use on pollinator diversity differ among taxa and scales

Datasets used in Ganuza et al. 2022: Interactive effects of climate and land use on pollinator diversity differ among taxa and scales. Local and regional data are provided in separate files for the environmental variables, plant species composition and the composition of the different pollinator taxa.

Adaptation to lower latitudes and lower elevations precedes the evolution of hummingbird pollination in western North American Penstemon

Premise: A switch in pollinator can occur when a plant lineage enters a new habitat where the ancestral pollinator is less common and a novel pollinator is more common. Since pollinator communities vary according to environmental tolerances and availability of resources, there may be consistent associations between pollination mode and specific regions and habitats. Such associations can be studied in lineages that have experienced multiple pollinator transitions, representing evolutionary replicates. Methods: Our study focused on a large clade of Penstemon wildflower species in western North America that has repeatedly evolved hummingbird-adapted flowers from ancestral bee-adapted flowers. For each species, we estimated geographic ranges from occurrence data and inferred environmental niches from climate, topographical, and soil data. Using a phylogenetic comparative approach, we investigated whether hummingbird-adapted species occupy distinct geographic regions or habitats relative to beeadapted species. Results: Hummingbird-adapted species occur at lower latitudes and lower elevations than bee-adapted species, resulting in a difference in their environmental niche. Hummingbird-adapted species seem to evolve in lineages that previously adapted to lower latitudes and elevations, since bee-adapted species sister to hummingbird-adapted species also occur in these regions and habitats. Sister species pairs – regardless of whether they differ in pollinator – show relatively little geographic range overlap. Conclusions: Adaptation to a novel pollinator may often occur in geographic and ecological isolation from ancestral populations. The ability of a given lineage to adapt to novel pollinators may critically depend on its ability to colonize regions and habitats associated with novel pollinator communities.

Stable species and interactions in plant-pollinator networks deviate from core position in fragmented habitats

Species and their interactions are more dynamic over time and space in fragmented habitats than in continuous habitats. In fragmented habitats, the low nestedness of mutualistic networks may be related to the position change of stable (high persistence over time/space) species and interactions in the networks. Previous studies have shown that stable species and interactions tend to be in the core position of mutualistic networks. However, in fragmented habitats, it remains unknown whether stable species or interactions still tend to be in the core position. To address this gap, here we evaluated the correlation between the position of proximity to the network core and the temporal/spatial stability of species and interactions, using the observation of 42 plant-pollinator networks conducted in a fragmented island landscape over 3 years. We showed that temporally/spatially stable species and interactions deviated from the network core to varying degrees. Temporally stable plants were most likely to deviate from the network core, followed by pollinators and interactions, while only spatially stable pollinators tend to deviate from the network core. When unstable species (present in few time/space points, typically specialists) and interactions occupy the network core, they cannot interact with most species in the network as generalists do, resulting in the decrease of network nestedness. Therefore, from the perspective of position and stability, stable species and interactions deviate from the network core in fragmented habitats, which is an important reason for the decrease of nestedness in mutualistic networks. Our study suggests that protecting plants that occupy the core in large plant-pollinator networks is essential for maintaining the network persistence in fragmented habitats.

Pollinator loss causes rapid adaptive evolution of selfing and dramatically reduces genome-wide genetic variability

While selfing populations harbor little genetic variation limiting evolutionary potential, the causes are unclear. We experimentally evolved large, replicate populations of Mimulus guttatus for nine generations in greenhouses with or without pollinating bees and studied DNA polymorphism in descendants. Populations without bees adapted to produce more selfed seed yet exhibited striking reductions in DNA polymorphism despite large population sizes. Importantly, the genome-wide pattern of variation cannot be explained by a simple reduction in effective population size, but instead reflects the complicated interaction between selection, linkage, and inbreeding. Simulations demonstrate that the spread of favored alleles at few loci depresses neutral variation genome-wide in large populations containing fully selfing lineages. It also generates greater heterogeneity among chromosomes than expected with neutral evolution in small populations. Genome-wide deviations from neutrality were documented in populations with bees, suggesting widespread influences of background selection. After applying outlier tests to detect loci under selection, two genome regions were found in populations with bees, yet no adaptive loci were otherwise mapped. Large amounts of stochastic change in selfing populations compromise evolutionary potential and undermine outlier tests for selection. This occurs because genetic draft in highly selfing populations makes even the largest changes in allele frequency unremarkable.

Data: Measuring plant attractiveness to pollinators: methods and considerations

Global pollinator declines have fostered increased public interest in creating pollinator-friendly gardens in human-managed landscapes. Indeed, studies on urban pollinator communities suggest that flower-rich greenspaces can serve as promising sites for conservation. Ornamental flowers, which are readily available at most commercial garden centers, are ubiquitous in these landscapes. These varieties are often non-native and highly bred, and their utility to pollinators is complex. In this study, we used observational data and citizen science to develop a methods framework that will assist stakeholders in the floriculture industry to incorporate metrics of pollinator health into existing breeding and evaluation protocols. The results of this study support how plant attractiveness to pollinators is often dependent on variables such as climate and plant phenology, which should be considered when developing an assessment tool. Furthermore, we found that some cultivars were consistently attractive across all observations while for other cultivars, pollinator visitation was apparently conditional. We determine using multiple statistical tests that 10 min is a sufficient length of time for observation of most plant types to broadly estimate three measures of plant attractiveness: visitor abundance, primary visitors attracted, and cultivar rank attractiveness, without sacrificing efficiency or accuracy. Additionally, we demonstrate that properly trained non-expert observers can collect accurate observational data, and our results suggest that protocols may be designed to maximize consistency across diverse data collectors.

opencc-zeroJun 2022View details →

Data from: Floral evolution and pollinator diversification in Hedychium: revisiting Darwin's predictions using an integrative taxonomic approach

Hedychium J.Koenig (Zingiberaceae) is endemic to the Indo-Malayan Realm and is known for its vibrant and fragrant flowers. Historically, two different pollination syndromes characterize Hedychium: diurnal or bird pollination and nocturnal or moth pollination. In this study we aim to understand the evolution of nocturnal and diurnal flowers, and to test its putative association with lineage diversification in Hedychium. A molecular tree of Hedychium was used as a scaffold upon which we estimated ancestral character-states, phylogenetic signals, and correlations for certain categorical and continuous floral traits. Further, we employed phylomorphospace and trait-dependent diversification rate estimation analyses to understand phenotypic evolution and associated lineage diversification in Hedychium. Although floral color and size lacked any association with specific pollinators, white or pale flowers were most common in the early branching clades, when compared to bright-colored flowers which were more widely represented in the most derived clade IV. Five categorical and two continuous characters were identified to have informative evolutionary patterns which also emphasized that ecology may have played a critical role in the diversification of Hedychium. From our phylogenetic analyses and ecological observations, we conclude that specializations in pollinator interactions are rare in the hyperdiverse clade IV, thus challenging the role of both moth-specialization and bird-specialization as central factors in the diversification of Hedychium. However, our results also suggest that clade III (predominantly island clade) may show specializations, and future studies should investigate ecological and pollinator interactions, along with inclusion of new traits such as floral fragrance and anthesis time.

opencc-by-4.0Jul 2022View details →

Transcriptomic analysis of deceptively pollinated Arum maculatum (Araceae) reveals association between terpene synthase expression in floral trap chamber and species-specific pollinator attraction

A compressed folder containing the R script and input files required to replicate the results in our manuscript entitled "Transcriptomic analysis of deceptively pollinated Arum maculatum (Araceae) reveals association between terpene synthase expression in floral trap chamber and species-specific pollinator attraction". Note: Raw Illumina sequencing files associated with this study have been uploaded to NCBI SRA, under the BioProject accession PRJNA856436. ABSTRACT Deceptive pollination often involves volatile organic compound (VOC) emissions that mislead insects into performing non-rewarding pollination. Among deceptively pollinated plants, Arum maculatum is particularly well-known for its potent dung-like VOC emissions and specialized floral chamber, which traps pollinators – mainly Psychoda phalaenoidesand P. grisescens – overnight. However, little is known about the genes underlying the production of many A. maculatumVOCs, and their influence on variation in pollinator attraction rates. Therefore, we performed de novo transcriptome sequencing of A. maculatum appendix and male floret tissue collected during- and post-anthesis, from ten natural populations across Europe. These RNA-seq data were paired with GC-MS analyses of floral scent composition and pollinator data collected from the same inflorescences. Differential expression analyses revealed candidate transcripts in appendix tissue linked to malodourous VOCs including indole, p-cresol, and 2-heptanone. Additionally, we found that terpene synthase expression in male floret tissue during anthesis significantly covaried with sex- and species-specific attraction of Psychoda phalaenoides and P. grisescens. Taken together, our results provide the first insights into molecular mechanisms underlying pollinator attraction patterns in A. maculatum, and highlight floral chamber sesquiterpene (e.g.bicyclogermacrene) synthases as interesting candidate genes for further study.

opencc-zeroDec 2021View details →

Floral phenology of an Andean bellflower and pollination by Buff-tailed Sicklebill

The Andean bellflowers comprise an explosive radiation correlated with shifts to specialized pollination. One diverse clade has evolved with extremely curved floral tubes and are predicted to be pollinated exclusively by one of two parapatric species of Sicklebill hummingbirds (Eutoxeres). In this study we focused on the floral biology of Centropogon granulosus, a bellflower thought to be specialized for pollination by E. condamini, in a montane cloud forest site in southeastern Peru. Using camera traps and a pollination exclusion experiment, we documented E. condamini as the sole pollinator of C.granulosus. Visitation by E. condamini was necessary for fruit development. Flowering rates were unequivocally linear and conformed to the 'steady state' phenological type. Over the course of >1800 hours of monitoring we recorded 12 E. condamini visits totaling 42 seconds, indicating traplining behaviour. As predicted by its curved flowers, C. granulosus is exclusively pollinated by Buff-tailed Sicklebill within our study area. We present evidence for the congruence of phenology and visitation as a driver of specialization in this highly diverse clade of Andean bellflowers.

opencc-zeroJul 2022View details →

Data from: Integrating effects of neighbor interactions for pollination

Animal-pollinated plants interact with neighbors for both abiotic resources and pollination, with consequences for reproduction and yield. Yet few studies have compared the relative magnitude of these effects, particularly in agroecosystems. In vertically stratified communities, such as agroforests, neighbor effects may be stratum-dependent. Understanding the net effects of neighbors on crop yield is important for managing multifunctional agroecosystems to simultaneously support production and biodiversity. This study evaluated the effects of neighboring plants on pollen deposition, fertilization, and yield in Coffea arabica in a shaded organic coffee farm with high non-crop plant abundance and diversity in Chiapas, Mexico. We assessed the impact of 1) floral resources at three vertical strata (herbs, coffee bushes, and canopy trees) on stigma pollen load (a measure of interaction for pollination), and 2) floral density and canopy cover (proxies for competition for abiotic resources) on yield (final fruit set and per-fruit weight), using structural equation modeling to evaluate the relative effect of each interaction type. Coffee competed for pollination with neighbors (conspecifics and heterospecifics) across strata. Pollen load influenced final fruit set, but the effect of neighbor competition for pollination was weaker than effects mediated by interaction for abiotic resources. Effects of interactions for abiotic resources were heterogeneous across strata, with negligible effects of herb-layer or coffee flower density but net positive effects of canopy trees on final fruit set. Overall effects of neighbors on coffee yield were weak, suggesting that coffee agroecosystems can be managed to maintain high plant density and diversity without sacrificing yield.

opencc-zeroJul 2022View details →

Rare and declining bee species are key to consistent pollination of wildflowers and crops across large spatial scales

Biodiversity promotes ecosystem function in experiments, but it remains uncertain how biodiversity loss affects function in larger-scale natural ecosystems, where rare and declining species which are likely to be lost and function needs to be maintained across space and time. Here we explore the importance of rare and declining bee species to the pollination of three wildflowers and three crops using large-scale (72 sites across 5,000 km2), multi-year datasets. Half (82/164) bee species were rare or declining, but these species provided ~15% of overall pollination. To determine the number of species important to ecosystem function, we used two methods of 'scaling up', both of which have previously been used for biodiversity-function analysis. First, we summed bee species' contributions to pollination across space and time and then found the minimum set of species needed to provide a threshold level of function across all sites; according to this method, effectively no rare and declining bee species were important to pollination. Second, we account for the "insurance value" of biodiversity by finding the minimum set of bee species needed to simultaneously provide a threshold level of function at each site in each year. The second method leads to the conclusion that 25 rare and eight declining bee species (36% and 53% of all rare and declining bee species, respectively) are important. Our findings provide some of the strongest evidence yet for the importance of rare and declining species, thereby providing a more direct link between real-world biodiversity loss and ecosystem function.

opencc-zeroJul 2022View details →

Long-term experimental drought alters floral scent and pollinator visits in a Mediterranean plant community despite overall limited impacts on plant phenotype and reproduction

Pollinators are declining globally, with climate change implicated as an important driver. Climate change can induce phenological shifts and reduce floral resources for pollinators, but little is known about its effects on floral attractiveness and how this might cascade to affect pollinators, pollination functions and plant fitness. We used an in situ long-term drought experiment to investigate multiple impacts of reduced precipitation in a natural Mediterranean shrubland, a habitat where climate change is predicted to increase the frequency and intensity of droughts. Focusing on three insect-pollinated plant species that provide abundant rewards and support a diversity of pollinators (Cistus albidus, Salvia rosmarinus and Thymus vulgaris), we investigated the effects of drought on a suite of floral traits including nectar production and floral scent. We also measured the impact of reduced rainfall on pollinator visits, fruit set and germination in S. rosmarinus and C. albidus. Drought altered floral emissions of all three plant species qualitatively, and reduced nectar production in T. vulgaris only. Apis mellifera and Bombus gr. terrestris visited more flowers in control plots than drought plots, while small wild bees visited more flowers in drought plots than control plots. Pollinator species richness did not differ significantly between treatments. Fruit set and seed set in S. rosmarinus and C. albidus did not differ significantly between control and drought plots, but seeds from drought plots had slower germination for S. rosmarinus and marginally lower germination success in C. albidus. Synthesis. Overall, we found limited but consistent impacts of a moderate experimental drought on floral phenotype, plant reproduction and pollinator visits. Increased aridity under climate change is predicted to be stronger than the level assessed in the present study. Drought impacts will likely be stronger and this could profoundly affect the structure and functioning of plant-pollinator networks in Mediterranean ecosystems.

opencc-zeroAug 2022View details →

The FloRes Database: A floral resources trait database for pollinator habitat-assessment generated by a multistep workflow

Background The decline of pollinating insects in agricultural landscapes proceeds due to intensive land use and the associated loss of habitat and food sources. The feeding of those insects depends on the spatial and temporal distribution of nectar and pollen as food resources. Hence, to protect insect biodiversity a spatio-temporal assessment of food quantity of their habitats is necessary. Therefore, sufficient data on traits of floral resources are required. New information Because floral resources' traits of plants are important to quantify food availability, we present two databases, the FloRes Database (Floral Resources Database) and the raw database, where FloRes was derived from. Both databases contain the plant traits (1) flowering period, (2) floral-unit density per day, (3) nectar volume per floral unit per day, (4) sugar content per floral unit, (5) sugar concentration in nectar, (6) pollen mass or volume per floral unit and per day, (7) protein content of pollen and (8) corolla depth. All traits are sampled from literature and online databases. The raw database consists of 702 specified plant species, 138 unspecified species 37 species (spec., sp), 22 species pluralis (spp) and for 79 only the genus was identified) and two species complexes (agg.). Those 842 taxa belong to 488 genera and 102 families. Finally, only 27 taxa have a complete set of traits, too less for a sufficient assessment of spatio-temporal availability of floral food resources. Because information of floral resources is scattered throughout many publications with different units, we also present our multistep workflow implemented in five consecutive R-scripts. The multistep workflow standardizes the trait units of the raw database to comparable entities with identical units and aggregates them on a reasonable taxonomic level into the second application database, the FloRes Database. Finally, the FloRes Database contains aggregated information of traits for 42 taxa and, when corolla depth is excluded, for 70 taxa. This is the first attempt to gather these eight traits from different literature sources in one database with a multistep workflow. The publication of the multistep workflow enables the users to extend the FloRes Database on their own demands with other literature data or newly gathered data to improve the quantification of food resources. Especially, the combination of pollen, nectar, and open flowers per square meter is, as far as we know, a novelty. The FloRes Database can be used to evaluate the quantity of food-resource habitats available for pollinators, e.g., to compare seed mixtures of agri-environmental measures, such as flower strips, considering flower phenology on a daily basis.

opencc-zeroDec 2021View details →

Pollination deficits and contributions of pollinators in apple production: a global meta-analysis

1. Apple is one of the most widely cultivated fruit crops worldwide, and apple yield benefits from pollination by insects. The global decline in wild pollinator populations raises concern about the adequacy of pollination services in apple production. 2. Here, we present a global meta-analysis of pollination in apple. We assembled from the literature a dataset comprising results of 48 studies across five continents on fruit set and seed set in apple with insect pollination, artificial pollination and pollinator exclusion, and analysed the effects of explanatory factors such as variety and continent. 3. Fruit set was on average 41% lower with open pollination than with artificial pollination, while seed set was 20% lower. These pollination deficits varied across continents and cultivars. Pollination deficits for fruit set were greatest in Asia (63%) followed by Europe (30%), whereas pollination deficits for seed set were greatest in Asia (47%) and South America (40%). Important differences in pollination deficit were also identified between cultivars but these differences were confounded with continent effects. 4. Fruit set and seed set were 71% and 62% higher, respectively, when insects had open access to flowers than when they were artificially excluded, while results varied among cultivars. 5. Synthesis and Applications. Globally, there are substantial contributions of pollinators to fruit set and seed set in apple, as well as considerable limitations in apple pollination services, particularly in Asia, Europe and South America. Several management strategies could be applied to reduce the pollination deficits in apple production: (1) conserving wild bees and enhancing their abundance and diversity, (2) using managed bees for pollination, (3) using varieties with low pollinator dependency, and/or (4) artificial pollination. These strategies should be tailored to the regional situation, considering the potential of landscapes for restoring wild pollinators, the acceptability of cultivated varieties for available pollinators, the acceptance in the market of self-compatible varieties, and the costs of management, such as artificial pollination, pollinator conservation, beekeeping and planting self-compatible varieties. Conservation of wild pollinators is preferred in regions with sufficient potential for wild pollinators as it contributes to biodiversity conservation and improves pollination in both crops and wild plants.