Examining the Role of Buzzing Time and Acoustics on Pollen Extraction of Solanum elaeagnifolium

Buzz pollination is a specialized pollination syndrome that requires vibrational energy to extract concealed pollen grains from poricidal anthers. Although a large body of work has examined the ecology of buzz pollination, whether acoustic properties of buzz pollinators affect pollen extraction is less understood, especially in weeds and invasive species. We examined the pollination biology of Silverleaf nightshade (Solanum elaeagnifolium), a worldwide invasive weed, in its native range in the Lower Rio Grande Valley (LRGV) in south Texas. Over two years, we documented the floral visitors on S. elaeagnifolium, their acoustic parameters (buzzing amplitude, frequency, and duration of buzzing) and estimated the effects of the latter two factors on pollen extraction. We found five major bee genera: Exomalopsis, Halictus, Megachile, Bombus, and Xylocopa, as the most common floral visitors on S. elaeagnifolium in the LRGV. Bee genera varied in their duration of total buzzing time, duration of each visit, and mass. While we did not find any significant differences in buzzing frequency among different genera, an artificial pollen collection experiment using an electric toothbrush showed that the amount of pollen extracted is significantly affected by the duration of buzzing. We conclude that regardless of buzzing frequency, buzzing duration is the most critical factor in pollen removal in this species.

The many elusive pollinators in the genus Amorphophallus

The genus Amorphophallus encompasses some 230 species and is one of the largest genera of the Araceae family. Most species release scents, smelling of carrion, faeces, dung and similar nauseating odours for pollinator attraction and are therefore considered to have evolved a deceptive pollination syndrome. Some of the most iconic members of the genus, such as the A. titanum and A. gigas, are considered to be carrion mimics. Copro-necrophagous insects, beetles and flies in particular, are attracted by these scents and are therefore assumed to act as pollinators. However, many reports and observations on Amorphophallus pollinators are anecdotal in nature or do not distinguish between legitimate pollinators and non-pollinating visitors. Moreover, some published observations are not readily accessible as they are many decades old. Therefore, the available data and information about insect visitors and/or pollinators in the genus Amorphophallus is compiled, reviewed and discussed.

Reproductive Biology and Pollination Ecology of Berberis lycium Royle: A Highly Valued Shrub of Immense Medicinal Significance

Study of reproductive biology and pollination ecology helps in understanding the life history patterns of species. Such a study brings to light the bottlenecks, if any, on account of which the individuals of the species are not able to reproduce in nature and ultimately helps in planning appropriate conservation strategies for the species under threat. The present study was aimed at examining the morphological and reproductive variance in Berberis lycium, a threatened ecological specialist growing within shrubberies and open hillsides of the North-Western Himalayas in India. B. lycium displays three different variants. Flowering period ranges from February to September. Pollen viability as reported on fluorescein diacetate and acetocarmine treatments was highest for variant I, while maximum pollen output was obtained for variant III. Pollen pistil interaction is brought by the movement of anther towards stigma. Fluorescence microscopy of hand pollinated club shaped stigma shows that the germinating pollen form a ring over the receptive adaxial surface. Pollination syndrome is entomophily. Variant II attracts a significantly large number of pollinators from diverse insect families. Breeding experiments reflect that plants are self-compatible and cross fertile. Reproductive output (% fruit set) was highest for variant II followed by III and I, respectively. This investigation helped to understand the effect of different biotic and abiotic constraints on the phenology and reproductive biology of the plant. The information generated so will enable conservationists to design appropriate strategies for its long-term survival and sustenance in nature.

The modern pollen–vegetation relationship in Jammu, India: a comparative appraisal

An understanding of the relationship between modern pollen and vegetation is a prerequisite for reconstruction of vegetation and climate change from fossil pollen records. We conducted palynological studies of thirty-five surface soil samples from the Jammu region of India, which revealed that Pinus, among the conifers (regional needle-leaved taxa), is over-represented in the pollen assemblage due to its high production and effective dispersal of pollen. Other coniferous and broadleaved (regional and/or extra-regional) taxa have comparatively lower values in the pollen assemblages, similar to the representation of subtropical deciduous forest elements (regional), as well as shrubby (regional and/or extra-regional) taxa. This inconsistency in the pollen assemblage could be due to long-distance transport of the former by wind and/or water from the higher reaches of the Himalayas, and also because the latter have an entomogamous pollination syndrome and are not high pollen producers. The recovered pollen assemblage presents a distorted picture of the extant vegetation; hence, caution should be exercised in interpreting fossil pollen records from the study area. Principal component analysis (PCA) shows variability in the distribution of pollen from different sites in the Jammu region, perhaps the result of transport (by wind and/ or water), altitude and/or edaphic factors of the Himalayan terrain. The study should improve our understanding of the modern pollen-vegetation relationship and aid further calibration and interpretation of fossil pollen records.

Rational Design of a Novel Hawkmoth Pollinator Interaction in Mimulus Section Erythranthe

Diversification of the ca. 275,000 extant flowering plant species has been driven in large part by coevolution with animal pollinators. A recurring pattern of pollinator shifts from hummingbird to hawkmoth pollination has characterized plant speciation in many western North American plant taxa, but in the genus Mimulus (monkeyflowers) section Erythranthe the evolution of hawkmoth pollination from hummingbird-pollinated ancestors has not occurred. We manipulated two flower color loci and tested the attractiveness of the resulting four color phenotypes (red, yellow, pink, and white) to naïve hawkmoths (Manduca sexta). Hawkmoths strongly prefer derived colors (yellow, pink, white) over the ancestral red when choosing an initial flower to visit, and generally preferred derived colors when total visits and total visit time were considered, with no hawkmoth preferring ancestral red over derived colors. The simple flower color genetics underlying this innate pollinator preference suggests a potential path for speciation into an unfilled hawkmoth-pollinated niche in Mimulus section Erythranthe, and the deliberate design of a hawkmoth-pollinated flower demonstrates a new, predictive method for studying pollination syndrome evolution.

Native and invasive ants affect floral visits of pollinating honey bees in pumpkin flowers (Cucurbita maxima)

Global pollinator decline is a major concern. Several factors—climate change, land-use change, the reduction of flowers, pesticide use, and invasive species—have been suggested as the reasons. Despite being a potential reason, the effect of ants on flowers received less attention. The consequences of ants being attracted to nectar sources in plants vary depending upon factors like the nectar source's position, ants' identity, and other mutualists interacting with the plants. We studied the interaction between flower-visiting ants and pollinators in Cucurbita maxima and compared the competition exerted by native and invasive ants on its pollinators to examine the hypothesis that the invasive ants exacerbate more interference competition to pollinators than the native ants. We assessed the pollinator's choice, visitation rate, and time spent/visit on the flowers. Regardless of species and nativity, ants negatively influenced all the pollinator visitation traits, such as visitation rate and duration spent on flowers. The invasive ants exerted a higher interference competition on the pollinators than the native ants did. Despite performing pollination in flowers with generalist pollination syndrome, ants can threaten plant-pollinator mutualism in specialist plants like monoecious plants. A better understanding of factors influencing pollination will help in implementing better management practices.

Ancient and recent introgression shape the evolutionary history of pollinator adaptation and speciation in a model monkeyflower radiation (Mimulus section Erythranthe)

Inferences about past processes of adaptation and speciation require a gene-scale and genome-wide understanding of the evolutionary history of diverging taxa. In this study, we use genome-wide capture of nuclear gene sequences, plus skimming of organellar sequences, to investigate the phylogenomics of monkeyflowers in Mimulus section Erythranthe (27 accessions from seven species). Taxa within Erythranthe, particularly the parapatric and putatively sister species M. lewisii (bee-pollinated) and M. cardinalis (hummingbird-pollinated), have been a model system for investigating the ecological genetics of speciation and adaptation for over five decades. Across >8000 nuclear loci, multiple methods resolve a predominant species tree in which M. cardinalis groups with other hummingbird-pollinated taxa (37% of gene trees), rather than being sister to M. lewisii (32% of gene trees). We independently corroborate a single evolution of hummingbird pollination syndrome in Erythranthe by demonstrating functional redundancy in genetic complementation tests of floral traits in hybrids; together, these analyses overturn a textbook case of pollination-syndrome convergence. Strong asymmetries in allele-sharing (Patterson’s D-statistic and related tests) indicate that gene-tree discordance reflects ancient and recent introgression rather than incomplete lineage sorting. Consistent with abundant introgression blurring the history of divergence, low-recombination and adaptation-associated regions support the new species tree, while high-recombination regions generate phylogenetic evidence for sister status for M. lewisii and M. cardinalis. Population-level sampling of core taxa also revealed two instances of chloroplast capture, with Sierran M. lewisii and Southern Californian M. parishii each carrying organelle genomes nested within respective sympatric M. cardinalis clades. A recent organellar transfer from M. cardinalis, an outcrosser where selfish cytonuclear dynamics are more likely, may account for the unexpected cytoplasmic male sterility effects of selfer M. parishii organelles in hybrids with M. lewisii. Overall, our phylogenomic results reveal extensive reticulation throughout the evolutionary history of a classic monkeyflower radiation, suggesting that natural selection (re-)assembles and maintains species-diagnostic traits and barriers in the face of gene flow. Our findings further underline the challenges, even in reproductively isolated species, in distinguishing re-use of adaptive alleles from true convergence and emphasize the value of a phylogenomic framework for reconstructing the evolutionary genetics of adaptation and speciation.

Floral biology of Salvia stachydifolia, a species visited by bees and birds: connecting sexual phases, nectar dynamics and breeding system to visitors’ behaviour

Aims Adaptive convergence in floral phenotype among plants sharing a pollinator guild has been acknowledged in the concept of pollination syndrome. However, many plants display traits associated with a given syndrome, but are visited by multiple pollinators. This situation may indicate the beginning of a pollinator shift or may result in a stable situation with adaptations to different pollinators. In Salvia stachydifolia, a previous study suggested that flower shape is optimized to maximize the contribution to pollination of bees and hummingbirds. Here, we studied three additional aspects of its floral biology: sexual phases, nectar dynamics and breeding system, and examined their connection with pollinators’ behavior to explore the presence of adaptations to bee and/or hummingbird pollination. Methods Using a greenhouse population, we applied five pollination treatments to characterize breeding system. To determine sexual phases, we recorded flower opening, anther dehiscence, corolla fall and stigma receptivity. Additionally, we characterized nectar volume and concentration dynamics along the day. Finally, to determine pollinator assemblage and visitation patterns, we performed field observations and recorded pollinators’ behavior. Important findings Salvia stachydifolia was partially protandrous and self-compatible, but open-pollinated plants attained the highest reproductive success, suggesting that reproduction is mainly dependent on pollinator activity. Bombus opifex bumblebees were the most frequent visitors, but Sappho sparganura hummingbirds dominated visits early in the morning and at dusk. Nectar was typical of bumblebee-pollination. We suggest that the bee-hummingbird mixed visitation constitutes an unstable evolutionary situation, making S. stachydifolia an ideal system to understand the ecological circumstances in which pollination shifts occur.

Wild bees as floral visitors to Salvia assurgens (Lamiaceae): a contribution to the pollination ecology of a white-flowered endemic Mexican sage

Background and Aims: Salvia assurgens (a white-flowered sage) is considered to be a melittophilous species due to its floral architecture. However, there are no current empirical data supporting its assignment to this pollination syndrome. The present study aimed to record the diurnal floral visitors of S. assurgens to confirm its characterization as melittophilous and to evaluate which species of bees are potential pollinators. Methods: We collected wild bee visitors to the flowers of one population of S. assurgens in northeastern Michoacán, Mexico, during the summers of 2018 and 2019. We analyzed the pollen loads of each bee species and body area. In addition, we recorded the behavior of some wild bees when visiting flowers of S. assurgens. Key results: Seventeen bee species from three families (Apidae, Halictidae, and Megachilidae) were recorded as floral visitors of S. assurgens. Ninety percent of pollen carried by the examined bees belonged to S. assurgens. Four species of wild bees were the most frequent visitors, with S. assurgens accounting for 94.2% of the pollen on their bodies. Notably, these species presented clear differences in the distribution of pollen on their body parts: two of them, Bombus pennsylvanicus sonorus and Megachile sp. 1 accumulated up to 90% of the pollen on the frons and dorsal area of their thorax. It is most likely that pollen is transferred from these body areas to the stigma of S. assurgens. Conclusions: The present study provides evidence of the melittophilous pollination syndrome of S. assurgens. The wild bee richness recorded in this study is as high as that previously reported in studies on floral visitors to Neotropical sages. Finally, our results highlight the usefulness of considering pollen loads to increase our knowledge of Salvia pollination ecology.