Pollen Dispersal Research Articles

Pollinators adjust their behavior to presence of pollinator-transmitted pathogen in plant population

Abstract Interactions between pollinators and plants can be affected by presence of plant pathogens that substitute their infectious propagules for pollen in flowers and rely on pollinators for transmission to new hosts. However, it is largely unknown how pollinators integrate cues from diseased plants such as altered floral rewards and floral traits, and how their behavior changes afterwards. Understanding pollinator responses to diseased plants is crucial for predicting both pathogen transmission and pollen dispersal in diseased plant populations. In this study, we investigated pollinator responses to contact with plants of Dianthus carthusianorum diseased with anther smut (Microbotryum carthusianorum). We combined three approaches: 1) observation of individual pollinators foraging in experimental arrays of pre-grown potted plants; 2) measurements of floral rewards and floral traits of healthy and diseased plants; and 3) quantification of pollen/spore loads of pollinator functional groups. We found that pollinators showed only weak preferences for visiting healthy over diseased plants, but after landing on plants, they probed fewer flowers on the diseased ones. Since diseased flowers offered lower nectar and no pollen rewards, this behavior is consistent with the prediction of optimal foraging models that pollinators should spend less time exploring less rewarding patches or plants. Furthermore, pollen-foraging solitary bees and hoverflies responded to diseased plants more negatively than nectar-feeding butterflies did. Lastly, based on group-specific behavior and typical pollen/spore loads, we suggest that solitary bees and hoverflies contribute to both pollen and pathogen spore dispersal mainly over short distances, while butterfly visits are most important for long-distance dispersal.

A new Early Miocene (Ottnangian) flora of the “Rzehakia Beds” from Brno-Líšeň

The fossil flora from brackish late Burdigalian (Ottnangian) sediments in Brno-Líšeň (the Czech Republic) contributes to our knowledge of floristic evolution and palaeoclimatic changes in the Western Carpathians. The fossil material investigated for this study comprises fragmentary leaf imprints, few fruits/seeds, and dispersed pollen from a single palynomorph-rich sample. Macro remains include 3 ferns (Osmunda parschlugiana, Salvinia reussii, ?Polypodiaceae gen. et sp. indet.) and 17 angiosperms (e.g., Daphnogene polymorpha, “Parrotia” pristina, Leguminophyllum spp., Podocarpium podocarpum, cf. Engelhardia orsbergensis, Ulmus sp., Schoenoplectiella cf. ragozinii). The palynospectrum comprises 106 taxa, including abundant palaeotropical elements of zonal evergreen forest, i.e., Sapotaceae, Palmae, Engelhardia, Platycarya, Fagaceae, Araliaceae and Cornus-Mastixia, accompanied by arctotertiary elements of deciduous zonal forest (Quercus, Carpinus, Fagus, Carya, Juglans, Tilia, Betula, Parrotia) and deciduous azonal (riparian) forest (e.g., Alnus, Salix, Ulmus). Aquatic plants, algae (Prasinophyceae, Botryococcus) and marine dinoflagellates indicate a marine environment with freshwater impact. Plant taxa possibly representing open areas such as Olea, Celtis, Buxus, Ephedra, Rosaceae and Poaceae are sporadic, as well as conifers of extrazonal forest such as Cedrus, Tsuga, Picea. The studied palynospectrum contains abundant thermophilic elements and does not point to a cooling event, as reported by previous authors from the Polish part of the Carpathian Foredeep.

Atmospheric transport reveals grass pollen dispersion distances

Identifying the origin of bioaerosols is of central importance in many biological disciplines, such as human health, agriculture, forestry, aerobiology and conservation. Modelling sources, transportation pathways and sinks can reveal how bioaerosols vary in the atmosphere and their environmental impact. Grass pollen are particularly important due to their widely distributed source areas, relatively high abundance in the atmosphere and high allergenicity. Currently, studies are uncertain regarding sampler representability between distance and sources for grass pollen. Using generalized linear modelling, this study aimed to analyse this relationship further by answering the question of distance-to-source area contribution. Grass pollen concentrations were compared between urban and rural locations, located 6.4 km apart, during two years in Worcestershire, UK. We isolated and refined vegetation areas at 100 m × 100 m using the 2017 CEH Crop Map and conducted atmospheric modelling using HYSPLIT to identify which source areas could contribute pollen. Pollen concentrations were then modelled with source areas and meteorology using generalized linear mixed-models with three temporal variables as random variation. We found that the Seasonal Pollen Integral for grass pollen varied between both years and location, with the urban location having higher levels. Day of year showed higher temporal variation than the diurnal or annual variables. For the urban location, grass source areas within 30 km had positive significant effects in predicting grass pollen concentrations, while source areas within 2–10 km were important for the rural one. The source area differential was likely influenced by an urban-rural gradient that caused differences in the source area contribution. Temperature had positive highly significant effects on both locations while precipitation affected only the rural location. Combining atmospheric modelling, vegetation source maps and generalized linear modelling was found to be a highly accurate tool to identify transportation pathways of bioaerosols in landscape environments.

ENHANCED CLINICAL EFFECTS OF CEDARCURE® TABLETS OF SUBLINGUAL IMMUNOTHERAPY OVER THE YEARS OF TREATMENT AND THE IMPACT OF OUTCOME BY COMBINED USE OF MITE SUBLINGUAL IMMUNOTHERAPY (DUAL SLIT) FOR JAPANESE CEDAR POLLINOSIS

We examined the clinical effects of Cedarcure® tablets for sublingual immunotherapy (SLIT), and examined the enhancement of the effects over the years of treatment. The subjects were 358 patients who treated with SLIT (126 of third year of treatment, 102 of second year, 130 of first year) in a single clinic. The clinical efficacy was evaluated with visual analog scale (VAS) of nose, eye and total symptoms during the peak season of moderate amount of pollen dispersal (2485 grains/cm2/season) in 2022. Concomitant medication scores were calculated by Japanese guidelines. Because many cases of combined use of mite SLIT (dual SLIT) were included in the subjects, we compared cedar SLIT alone and dual SLIT as a secondary analysis. Clinical efficacy improved with the years of treatment, and all assessments of VAS in the 3rd year were significantly better than in the 1st year of treatment (p<0.01). The third year was better with sneezing and nasal discharge than the 2nd year, and the 2nd year was better with itchy eyes than the 1st year (p<0.05). Drug scores were also lower in the 3rd and 2nd years than in the 1st year (p<0.05). Additional mite SLIT did not affect the results. Cedarcure® showed enhancement of the effects over the years of treatment by the analysis up to the third year. Both Cedar SLIT alone and Dual SLIT showed similar efficacy on cedar pollinosis.

Relationship between Large amounts of Cryptomeria Japonica D. Don Pollen Dispersion and Cold Front Passage

Relationship between Large amounts of Cryptomeria Japonica D. Don Pollen Dispersion and Cold Front Passage

Temperature as the main factor affecting the reproductive phenology of the dioecious palm Mauritiella armata (Arecaceae)

Our research focused on the reproductive phenology of Mauritiella armata, a key veredas species in southeastern Brazil, and aspects of its floral and fruit morphology and sexual system. We observed the reproductive phenological patterns of M. armata for 36 months, and examined the relationships between phenophases and environmental variables to describe its phenological patterns in relation to environmental filters, as well as its floral and fruit morphologies, sexual system (to evaluate dioecy), and the biometry of its reproductive parts. Flowering was observed in the dry season and at the beginning of the rainy season, with fruiting occurring during the rainy season. The reproductive phenophases responded to environmental seasonality, principally temperature in the period immediately preceding the expression of the phenophase, as well as to environmental variations that had occurred up to six months earlier. The dioecious sexual system of M. armata was confirmed, with flowering synchronization between the sexes. The population studied did not exhibit apomixis, having xenogamy as its reproductive system. The staminate inflorescences were larger than the pistillate inflorescences and had greater numbers of flowers, although the pistillate flowers were larger. Wind pollen dispersal was not observed, thereby indicating that this species requires biotic pollination for fruit production.

Improved model for the predictions of Japanese cedar pollen dispersion and counts in Fukushima City

Improved model for the predictions of Japanese cedar pollen dispersion and counts in Fukushima City

Data Mining Methods to Detect Airborne Pollen of Spring Flowering Arboreal Taxa

Variations in the airborne pollen load are among the current and expected impacts on plant pollination driven by climate change. Due to the potential risk for pollen-allergy sufferers, this study aimed to analyze the trends of the three most abundant spring-tree pollen types, Pinus, Platanus and Quercus, and to evaluate the possible influence of meteorological conditions. An aerobiological study was performed during the 1993–2020 period in the Ourense city (NW Spain) by means of a Hirst-type volumetric sampler. Meteorological data were obtained from the ‘Ourense’ meteorological station of METEOGALICIA. We found statistically significant trends for the Total Pollen in all cases. The positive slope values indicated an increase in pollen grains over the pollen season along the studied years, ranging from an increase of 107 to 442 pollen grains. The resulting C5.0 Decision Trees and Rule-Based Models coincided with the Spearman’s correlations since both statistical analyses showed a strong and positive influence of temperature and sunlight on pollen release and dispersal, as well as a negative influence of rainfall due to washout processes. Specifically, we found that slight rainfall and moderate temperatures promote the presence of Pinus pollen in the atmosphere and a marked effect of the daily thermal amplitude on the presence of high Platanus pollen levels. The percentage of successful predictions of the C5.0 models ranged between 62.23–74.28%. The analysis of long-term datasets of pollen and meteorological information provides valuable models that can be used as an indicator of potential allergy risk in the short term by feeding the obtained models with weather prognostics.

Context matters: the landscape matrix determines the population genetic structure of temperate forest herbs across Europe

ContextPlant populations in agricultural landscapes are mostly fragmented and their functional connectivity often depends on seed and pollen dispersal by animals. However, little is known about how the interactions of seed and pollen dispersers with the agricultural matrix translate into gene flow among plant populations.ObjectivesWe aimed to identify effects of the landscape structure on the genetic diversity within, and the genetic differentiation among, spatially isolated populations of three temperate forest herbs. We asked, whether different arable crops have different effects, and whether the orientation of linear landscape elements relative to the gene dispersal direction matters.MethodsWe analysed the species’ population genetic structures in seven agricultural landscapes across temperate Europe using microsatellite markers. These were modelled as a function of landscape composition and configuration, which we quantified in buffer zones around, and in rectangular landscape strips between, plant populations.ResultsLandscape effects were diverse and often contrasting between species, reflecting their association with different pollen- or seed dispersal vectors. Differentiating crop types rather than lumping them together yielded higher proportions of explained variation. Some linear landscape elements had both a channelling and hampering effect on gene flow, depending on their orientation.ConclusionsLandscape structure is a more important determinant of the species’ population genetic structure than habitat loss and fragmentation per se. Landscape planning with the aim to enhance the functional connectivity among spatially isolated plant populations should consider that even species of the same ecological guild might show distinct responses to the landscape structure.

Dosing intact birch pollen grains at the air-liquid interface (ALI) to the immortalized human bronchial epithelial cell line BEAS-2B.

In real life, humans are exposed to whole pollen grains at the air epithelial barrier. We developed a system for in vitro dosing of whole pollen grains at the Air-Liquid Interface (ALI) and studied their effect on the immortalized human bronchial epithelial cell line BEAS-2B. Pollen are sticky and large particles. Dosing pollen needs resuspension of single particles rather than clusters, and subsequent transportation to the cells with little loss to the walls of the instrumentation i.e. in a straight line. To avoid high speed impacting insults to cells we chose sedimentation by gravity as a delivery step. Pollen was resuspended into single particles by pressured air. A pollen dispersion unit including PTFE coating of the walls and reduced air pressure limited impaction loss to the walls. The loss of pollen to the system was still about 40%. A linear dose effect curve resulted in 327-2834 pollen/cm2 (± 6.1%), the latter concentration being calculated as the amount deposited on epithelial cells on high pollen days. After whole pollen exposure, the largest differential gene expression at the transcriptomic level was late, about 7 hours after exposure. Inflammatory and response to stimulus related genes were up-regulated. We developed a whole pollen exposure air-liquid interface system (Pollen-ALI), in which cells can be gently and reliably dosed.

Establishment of local adaptation in partly self-fertilizing populations.

Populations often inhabit multiple ecological patches and thus experience divergent selection, which can lead to local adaptation if migration is not strong enough to swamp locally adapted alleles. Conditions for the establishment of a locally advantageous allele have been studied in randomly mating populations. However, many species reproduce, at least partially, through self-fertilization, and how selfing affects local adaptation remains unclear and debated. Using a two-patch branching process formalism, we obtained a closed-form approximation under weak selection for the probability of establishment of a locally advantageous allele (P) for arbitrary selfing rate and dominance level, where selection is allowed to act on viability or fecundity, and migration can occur via seed or pollen dispersal. This solution is compared to diffusion approximation and used to investigate the consequences of a shift in a mating system on P, and the establishment of protected polymorphism. We find that selfing can either increase or decrease P, depending on the patterns of dominance in the two patches, and has conflicting effects on local adaptation. Globally, selfing favors local adaptation when locally advantageous alleles are (partially) recessive, when selection between patches is asymmetrical and when migration occurs through pollen rather than seed dispersal. These results establish a rigorous theoretical background to study heterogeneous selection and local adaptation in partially selfing species.

Long distance pollen dispersal and intrapopulation genetic structure determined by clonal diversity in Hymenaea stigonocarpa populations of the Brazilian savanna

Long distance pollen dispersal and intrapopulation genetic structure determined by clonal diversity in Hymenaea stigonocarpa populations of the Brazilian savanna

Variations in airborne pollen and spores in urban Guangzhou and their relationships with meteorological variables

Airborne pollen causes various types of allergies in humans, and the extent of allergic infection is related to the presence of different types of sporo–pollen and existing meteorological conditions in a certain area. Therefore, an aeropalynological study of 72 airborne samples with a hydrofluoric acid (HF) treatment was conducted in the Haizhu district of Guangzhou, China, in 2016, to identify the temporal variations in airborne sporo–pollen and the relationship between airborne sporo–pollen concentrations and different meteorological variables in Guangzhou, China. Forty-five types of airborne pollen, seven types of airborne spores, and some undetermined sporo–pollen taxa were identified with two separate plant habitats occurring during this period (from January to December 2016): arboreal pollen (tree-based) and non-arboreal pollen (herb, shrub, aquatic, liane, etc.). Furthermore, the daily records of four key meteorological variables (temperature, precipitation, relative humidity, and wind speed) were acquired to distinguish the pollen seasons and correlated with Spearman's rho test to establish a pollen-weather data book with the seasonal variations. The two leading seasons were identified based on pollen abundance: spring and autumn. Among them, the primary dominant sporo–pollen families during the spring season were Poaceae, Pinaceae, Euphorbiaceae, Moraceae, Microlepia sp., and Polypodiaceae. Conversely, Artemisia sp., Asteraceae, Cyperaceae, Poaceae, Alnus sp., Corylus sp., Myrtaceae, and Rosaceae were the dominant pollen species during autumn. However, few pollen grains were identified in January, May–July, and December. The statistical analysis revealed that temperature had both positive and negative correlations with sporo–pollen concentrations. However, precipitation and relative humidity had a strong impact on the sporo–pollen dispersion and exhibited a negative correlation with the sporo–pollen concentrations. The wind speed had a positive but strong correlation with the sporo–pollen concentration during the study period. Some inconsistent results were found due to environmental variations, vegetation type, and climate change around the study area. This study will facilitate the identification of pollen seasons to prevent the occurrence of pollen-related allergies in the Guangzhou city area.

Development of highly polymorphic microsatellite markers for Campanula glomerata L. (Campanulaceae).

Campanula glomerata L. (Campanulaceae) is a self-incompatible, insect-pollinated herb occurring in calcareous grasslands, and is declining and (critically) endangered in many parts of its European distribution range. It often exists as small and isolated populations. A recovery plan of C. glomerata has been implemented in southern Belgium, involving plant translocations. We developed microsatellite markers using an enriched genomic library and characterized 16 loci in 111 individuals from eight populations. These 16 loci were highly polymorphic, with 11 to 31 alleles per locus for a total of 329 alleles, and expected heterozygosity (He) ranging from 0.470 to 0.938. These highly polymorphic loci constitute a promising tool for detailed genetic analyses: assigning individuals to distinct multilocus genotypes will allow quantifying pollen dispersal, clonal propagation and sexual recruitment and identifying admixed seed progeny and their pollen donors. Evaluating the genetic status of existing populations and a genetic monitoring of the translocated populations will contribute to optimize success in restoring viable and evolutionary resilient populations.

Genotypic variability of Sorbus domestica in Central Europe revealed by the SSR markers

The service tree (Sorbus domestica) is a rare tree species with a scarce distribution across Europe. In Central Europe, where it occurs at northern distribution limits, it is confined to several areas with a very scattered distribution affected by the human impact on the landscape. In this study, we aimed to understand the genetic diversity of its Central European population in a fragmented landscape and its relationship to the origin of different populations. We used 5 microsatellite loci to analyse 189 individuals from 13 populations, mainly from Central Europe with additional sampling from other parts of Europe and Asia. Standard population genetic characteristics and investigation on population structure revealed relatively high genetic diversity within populations, suggesting long-distance pollen dispersal and/or dispersion influenced by humans. All populations showed weak to moderate genetic differentiation, revealing that the marginal Central European population forms clusters that are linked to other Pannonian or Mediterranean populations, whereas Bohemian ones are linked to German populations, suggesting different origins for the populations in the eastern vs. western parts of Central Europe. Genetic variation suggests a natural continuum with neighbouring populations; however, relatively high genetic variation, the character of localities and population structure suggest an anthropogenic origin.

Pollen productivity estimates strongly depend on assumed pollen dispersal II: Extending the ERV model

Pollen productivity estimates (PPEs) are a key parameter for quantitative land-cover reconstructions from pollen data. PPEs are commonly estimated using modern pollen-vegetation data sets and the extended R-value (ERV) model. Prominent discrepancies in the existing studies question the reliability of the approach. We here propose an implementation of the ERV model in the R environment for statistical computing, which allows for simplified application and testing. Using simulated pollen-vegetation data sets, we explore sensitivity of ERV application to (1) number of sites, (2) vegetation structure, (3) basin size, (4) noise in the data, and (5) dispersal model selection. The simulations show that noise in the (pollen) data and dispersal model selection are critical factors in ERV application. Pollen count errors imply prominent PPE errors mainly for taxa with low counts, usually low pollen producers. Applied with an unsuited dispersal model, ERV tends to produce wrong PPEs for additional taxa. In a comparison of the still widely applied Prentice model and a Lagrangian stochastic model (LSM), errors are highest for taxa with high and low fall speed of pollen. The errors reflect the too high influence of fall speed in the Prentice model. ERV studies often use local scale pollen data from for example, moss polsters. Describing pollen dispersal on his local scale is particularly complex due to a range of disturbing factors, including differential release height. Considering the importance of the dispersal model in the approach, and the very large uncertainties in dispersal on short distance, we advise to carry out ERV studies with pollen data from open areas or basins that lack local pollen deposition of the taxa of interest.

High population density of bee pollinators increasing Camelina sativa (L.) Crantz seed yield: Implications on the potential risk for insect-mediated gene flow

New Camelina sativa genotypes have been genetically engineered (GE) to produce unique high-value chemical compounds and biofuel products. However, baseline information on predictive environmental risk assessment on this plant is urgently needed to establish guidelines for commercial large-scale production. Pollinating insects such as bees could facilitate the spread of transgenes into the ecosystem and raises ecological concerns on insect-mediated gene flow. Thus determination of the potential impact of pollinating insects on C. sativa pollination and gene flow becomes important. A 4-year experiment conducted in Connecticut, USA (2017) and Yangzhou, China (2019–2021) was carried out to determine the pollination effect of different densities of honey bees (Apis mellifera L.) populations on C. sativa seed yield and assess their involvement on C. sativa pollen dispersal. Insect cages experiments with presence or absence of honey bees showed that C. sativa seed yield was not affected by a relatively low population density of honey bees (20 honey bees m−2). However, at a higher density of honey bee population, Camelina sativa seed yield (0.23 g plant-1 and 73.3 g m−2) was statistically greater than those of the uncaged control (0.21 g plant-1 and 68.9 g m−2), caged C. sativa plants without honey bees (0.20 g plant-1 and 66.3 g m−2) or with 20 honey bees m−2 (0.21 g plant-1 and 66.9 g m−2), although C. sativa is commonly assumed to be self-pollinated. Principle coordinate analysis (PCoA) made from SSR markers revealed that honey bee and bumble bee are able to transfer C. sativa pollen from pollen source to adjacent flowers of other species (e.g., Brassica juncea, Brassica napus) up to 10−15 m beyond the field edge, raising ecological concerns on insect-mediated gene flow between adjacent C. sativa fields particularly if GE C. sativa cultivars are involved. The new information in this study will help to better understand C. sativa pollination biology, environmental risks associated with insect-mediated gene flow, and develop management strategies to reduce gene flow and facilitate coexistence between GE and non-GE C. sativa under natural agroecosystem.

Comparison of reproductive organs structure in various genotypes of Phaseolus vulgaris grown under the same conditions in Mersin, Turkey

The common bean (Phaseolus vulgaris) is a plant having hermaphroditic flowers, which are self-fertilizing. Common bean is a important commercial crop and one of Turkey’s most valuable grain legumes for human consumption. Genetic variation exists within and between bean populations. These variations can have an impact on the plants morphology, including reproductive organs. Variations in size and length of reproductive organs may cause different cell numbers and various fertilization successes. In this study, the response of four determinate common bean genotypes (Akman, Bitlis 117, Göksun, and Karacaşehir) to reproductive organ structure was studied. Plants were grown at 21/16 °C (day/night) and 12 h photoperiod in a greenhouse in Mersin, Turkey. Besides focusing mainly on pollen development, fertilization success factors such as pod and seed set were also assessed. Pod and seed set were evaluated numerically for each genotype. For pollen morphology, flower buds of the equal growth stage of all four bean genotypes were collected, and these samples were analyzed by scanning electron microscopy. The species have distinct morphological characteristics concerning pollen size, ornamentation patterns of the exine, and endoaperture type. It is also crucial to examine pollen dispersion in the pollinated flowers, as it may influence reproductive success. However, pollen wall architecture was similar in all genotypes tested. Despite general morphological similarity, differences in pollen viability and pod and seed number were observed. Although Akman genotype had the largest flowers, the Karacaşehir genotype was found to be the most productive one. The findings presented here can be helpful for researchers studying bean breeding and those investigating the morphological variation in different Phaseolus genotypes.

Expansion of the rare Eucalyptus risdonii under climate change through hybridization with a closely related species despite hybrid inferiority.

Hybridization is increasingly recognized as an integral part of the dynamics of species range expansion and contraction. Thus, it is important to understand the reproductive barriers between co-occurring species. Extending previous studies that argued that the rare Eucalyptus risdonii was expanding into the range of the surrounding E. amygdalina by both seed and pollen dispersal, we here investigate the long-term fitness of both species and their hybrids and whether expansion is continuing. We assessed the survival of phenotypes representing a continuum between the two pure species in a natural hybrid swarm after 29 years, along with seedling recruitment. The performance of pure species as well as of artificial and natural hybrids was also assessed over 28 years in a common garden trial. In the hybrid zone, E. amygdalina adults showed greater mortality than E. risdonii, and the current seedling cohort is still dominated by E. risdonii phenotypes. Morphologically intermediate individuals appeared to be the least fit. Similar results were observed after growing artificial first-generation and natural hybrids alongside pure species families in a common garden trial. Here, the survival, reproduction, health and growth of the intermediate hybrids were significantly less than those of either pure species, consistent with hybrid inferiority, although this did not manifest until later reproductive ages. Among the variable progeny of natural intermediate hybrids, the most E. risdonii-like phenotypes were the most fit. This study contributes to the increasing number of reports of hybrid inferiority in Eucalyptus, suggesting that post-zygotic barriers contribute to the maintenance of species integrity even between closely related species. However, with fitness rapidly recovered following backcrossing, it is argued that hybridization can still be an important evolutionary process, in the present case appearing to contribute to the range expansion of the rare E. risdonii in response to climate change.

New Fagaceous pollen taxa from the Miocene Søby flora of Denmark and their biogeographic implications.

The Fagaceae comprise around 1000 tree species in the Northern Hemisphere. Despite an extensive fossil pollen record, reconstructing biogeographic patterns is hampered because it is difficult to achieve good taxonomic resolution with light microscopy alone. We investigate dispersed pollen of Fagaceae from the Miocene Søby flora, Denmark. We explore the latitudinal gradient in Fagaceae distribution during the Miocene Climatic Optimum (MCO) in Europe and the Northern Hemisphere to compare it with the Eocene Warmhouse and the present. We investigated dispersed pollen using light and scanning electron microscopy. We assessed biogeographic patterns in Fagaceae during two warm periods in Earth history (MCO, Eocene) and the present. Eight species of Fagaceae were recognized in the Søby flora. Of these, Fagus had a continuous Mediterranean to subarctic distribution during MCO; Quercus sect. Cerris and castaneoids had northern limits in Denmark, and evergreen Quercus sect. Ilex in Central Europe. In a northern hemispheric context, Fagus and sections of Quercus had more northerly distribution limits during Eocene and MCO with maximum northward extensions during Eocene (Fagus, castaneoids) or Oligo-Miocene (Quercus sects. Cerris and Ilex). The known distribution of the extinct Tricolporopollenites theacoides during MCO included Central Europe and East China, while this taxon thrived in South China during Eocene. More northerly distributions during MCO and Eocene probably were determined by temperature. In contrast, fossil occurrences in areas that are arid or semi-humid today were determined by maritime conditions in these areas (western North America, Central Asia) during the Cenozoic.