Occurrence Of Pollen Research Articles

The age, palaeoclimate, palaeovegetation, coal seam architecture/mire types, paleodepositional environments and thermal maturity of syn-collision paralic coal from Mukah, Sarawak, Malaysia

The Mukah coal accumulated in the Balingian Formation where the time-stratigraphic position is poorly defined by fauna, though a probable Late Miocene age has always been assigned to this formation. Samples collected in the present study that yielded an abundance of Casuarina pollen associated with occurrences of Dacrydium, Stenochlaena palustris, Florschuetzia levipoli and also Stenochlaena areolaris spores, compare closely to zone PR9 of the palynological zonation of the Malay Basin, and can be tied to depositional sequences of Malay Basin Seismic sequences I2000/I3000, indicating an Early Miocene age for the studied coal. The Early Miocene age shows that the Mukah coal was formed during the collision between Luconia Block–Dangerous Grounds with the Borneo that lasted from Late Eocene to late Early Miocene. The rapid increase of deposition base-level caused by the collision is clearly reflected by the architecture of the Mukah coal seams that were generally thin, and also by the reverse order of the paleo-peat bodies.The studied coal samples contained large amounts of detrohuminite without the enrichment of liptinite group macerals, usually explained by the dominance of herbaceous plants in the paleomires. However, the pollen assemblages recovered in the present study provide no support for a ‘herbaceous’ swamp, instead the peats were likely formed mainly from forest vegetation based on the recovery of dominant arboreal pollen assemblages in the present study. Palynomorph assemblages recovered in the present study, with abundance of Casuarina pollen associated with common occurrences of Dacrydium, strongly suggest Kerangas vegetation and Kerapah type peat swamps, indicating a very wet climate. The occurrence of rattan and Pandanus pollens shows that the kerapah type peat swamps were locally bordered by rattan and Pandanus swamps. This shows that the prevailing use of coal petrography to discern the type of vegetation that was present in the peat-forming mires may lead to wrong conclusions. Therefore, a multi-disciplinary approach must be applied for a more accurate and reliable spatial interpretation of the type of vegetation that was present in the peat-forming mires.Consistent with the low sulphur content, evidence from the palynomorph assemblages recovered from the coal seams shows that the coal-forming peat was deposited in freshwater mires with little or no marine influence, despite the fact that the accumulation of the Mukah coal-forming peat took place within a coastal plain setting. Moreover, the fauna present in the host rock formation also suggested a brackish-water environment of deposition.

Genomic relationships between hexaploid Helianthus resinosus and diploid Helianthus annuus (Asteraceae)

Genus Helianthus comprises diploid and polyploid species. An autoallopolyploid origin has been proposed for hexaploid species but the genomic relationships remain unclear. Mitotic and meiotic studies in annual Helianthus annuus (2n = 2x = 34) and perennial Helianthus resinosus (2n = 6x = 102) as well as the F1 hybrids between both species were carried out. Chromosome counting confirmed the hybrid origin of the latter plants and their tetraploid condition. Bivalents in hybrids ranged from 12 to 28 (\( \bar{x} \) = 20.8). Univalents, trivalents and quadrivalents were also observed. Meiotic products comprised dyads, triads and normal tetrads and pollen grains were heterogeneous in size. These observations suggest the occurrence of 2n pollen in addition to the expected n. Genomic in situ hybridization (GISH) of total H. annuus DNA on H. resinosus chromosomes rendered weak but uniform signals; similar hybridization pattern was observed using three other annual species. Hybridization with H. annuus probe performed on root tip cells of F1H. annuus × H. resinosus hybrids revealed 17 chromosomes with a strong hybridization signal. GISH in hybrid meiocytes distinguished chromosomes from parental species and revealed autosyndetic pairing of H. resinosus chromosomes, allosyndetic pairing in bivalents, trivalents and quadrivalents, and the presence of univalents derived from parents, H. annuus and H. resinosus. Results obtained from classical and molecular cytogenetics do not support H. annuus as a direct ancestor of H. resinosus. The occurrence of allosyndetic pairing and the relatively high fertility of the F1 hybrids point to the possibility that useful genes could be transferred from H. resinosus to cultivate sunflower, although the effective rate of recombination has not been evaluated. GISH method proved effective to recognize parental chromosomes in H. annuus × H. resinosus progeny.

Late Quaternary history of a Mediterranean temporary pool from western Morocco, based on sedimentological and palynological evidence

Using sedimentological and pollen analysis, a reconstruction is presented here for the origin and history of a temporary pool from the quartzitic-sandstone Benslimane Plateau (W. Morocco). The pool is one of many that originated from the dismantling of a past hydrographical network, dated to the end of the Lower Pleistocene. Infilling of the pool began only recently between 5000 and 4000cal. BP, and probably was in response to Neolithic-induced degradation of the regional vegetation cover. The almost continuous pollen occurrence of Isoetes velata-type, Myriophyllum alterniflorum and Ranunculus-type throughout the palynological sequence indicates that the organisation of local plant communities in concentric belts (a central aquatic community, an intermediate amphibious one, and a peripheral terrestrial one) has remained unchanged since the Mid-Holocene. The stability of the vegetation structure and composition over more than 4000years confirms the adaptation of the hydrophytic communities to human-induced disturbances (mainly grazing).The long-term pool longevity is attributed to an equilibrium between wind erosion and sedimentation. The sediment accumulation balance that was null or negative during most of the Pleistocene became positive under the influence of Neolithic activities, which may also be linked to unfavourable climatic conditions. These results have important implications for the long-term conservation of biodiversity, as these rare habitats are rapidly declining. Since temporary pools also protect the quartzitic-sandstone plateau from erosion, their disappearance could trigger the reorganisation of the hydrological network and the resumption of soil erosion.

The patterns of Corylus and Alnus pollen seasons and pollination periods in two Polish cities located in different climatic regions.

This study compares phenological observations of Corylus (hazel) and Alnus (alder) flowering with airborne pollen counts of these taxa recorded using volumetric spore traps (2009–2011). The work was carried out in the Polish cities of Szczecin and Rzeszów that are located in different climatic regions. Correlations between pollen concentrations and meteorological data were investigated using Spearman’s rank correlation analysis. The timings of hazel and alder pollination and the occurrence of airborne pollen varied greatly and were significantly influenced by meteorological conditions (p < 0.05). The flowering synchronization of hazel and alder pollination in Szczecin and Rzeszów varied over the study period. Hazel and alder trees flowered notably earlier in stands located in places that were exposed to sunlight (insolated) and sheltered from the wind. On the other hand, a delay in the timing of pollination was observed in quite sunny but very windy sites. In Rzeszów, maximum hazel pollen concentrations did not coincide with the period of full pollination (defined as between 25 % hazel and alder and 75 % of flowers open). Conversely, in Szczecin, the highest hazel pollen concentrations were recorded during phenophases of the full pollination period. The period when the highest alder pollen concentrations were recorded varied between sites, with Rzeszów recording the highest concentrations at the beginning of pollination and Szczecin recording alder pollen throughout the full pollination period. Substantial amounts of hazel and alder pollen grains were recorded in the air of Rzeszów (but not Szczecin) before the onset of the respective pollen seasons.

A new Middle Pleistocene interglacial record from Denmark: Chronostratigraphic correlation, palaeovegetation and fire dynamics

Previously only three terrestrial interglacial periods were known from southern Scandinavia, all of which could be relatively easily correlated within the central European stratigraphical framework. Here, we present a new interglacial–interstadial pollen, plant macrofossil and charcoal record from Trelde Klint, Denmark, and analyse its biostratigraphy, correlation with other European records, vegetation development, fire dynamics and absolute dating. Except for a slight truncation of the early part of the record, the pollen stratigraphy exhibits a full interglacial succession, including temperate trees (Quercus, Ulmus and Tilia) during its mesocratic stage. Macrofossil analysis allowed identification to species level for Quercus robur, Picea abies and two mosses. Conifers (Pinus and Picea) dominate the pollen record of the interglacial sequence, and the occurrence of Larix pollen in the top part of the interglacial record as well as in the interstadial sediments is especially indicative of this interglacial. The overall diversity of tree genera is rather low. These biostratigraphical features suggest that Trelde Klint is unique among Danish records, but it is similar to records from northern Germany. Numerical analyses (REVEALS and DCA) indicate that forests during the temperate stage were dense and that vegetation openness increased only towards the end of the interglacial, accompanied by increased fire occurrence. A short interstadial sequence with a dominance of Pinus and Betula and the presence of Larix is present above the interglacial deposit. We argue that lack of attention to differences in fire regimes may hamper understanding of between‐site correlations of interglacial pollen records. OSL dating, using a novel feldspar technique, yields an average age of 350±20 ka for the sandy sediments above the interglacial layers at Trelde Klint, suggesting that the whole interglacial–interstadial succession belongs to Marine Isotope Stage 11.

Gamma-induced infraspecific polyploidy via cytomixis-mediated syncyte formation in Papaver somniferum (Papaveraceae)

This is the first report on the phenomenon of syncyte manifestation through cytomictic transmigration in Papaver somniferum L. The occurrence characteristics and cytological depictions of cytomixis in the meiotic course of gamma-irradiated population reveal the mechanism leading to the origin of the cell fusions/syncytes. The event was more frequent in meiosis I and rare in meiosis II, indicating that the process atrophies at the end of the first meiotic division. The degree of occurrence of the phenomenon virtually concurred with the increase in the treatment dose of gamma irradiation. The phenomenon also affected the qualitative composition of postmeiotic products, i.e. tetrads and pollen grains. Heterosized pollen grains ranging from large to small size are also reported. In general, the occurrence of large-sized pollens is associated with unreduced gametes/syncytes and is an indication of the production of 2n pollens. Although occurring in low frequency, syncytes could play a decisive role in plant evolution as they can lead to the production of plants with higher ploidy levels. They may have potential applications in germplasm improvement in the sense of diversity and thus should be given more attention in future studies.

Modern pollen assemblages of surface samples from Cherrapunjee and its adjoining areas, Meghalaya, northeast India

Cherrapunjee, the wettest place on Earth, holds two Guinness Book of World Records for receiving the maximum amount of rainfall in a single year and in a single month. A dataset of 65 surface pollen samples from Cherrapunjee, the gateway of the Indo-Burma hotspot region, was analyzed in order to explore the relationship between the modern pollen assemblage and contemporary vegetation patterns. The study reveals the occurrence of subtropical pine forest along with broad-leaved taxa with scattered patches of Pandanus during the recent past. Due to large scale deforestation and massive soil erosion (wettest area), the flora gradually converted into grassland under a xeric climate. Laitkynsew is enriched with evergreen forest consisting of Lauraceae, Mesua and Schima along with patches of Pandanus and Rhizophoraceae indicating high precipitation under the influence of coastal habitation. However, other areas such as the Duwan Sing Syiem Bridge show primary subtropical pine forest with broad-leaved taxa, which are gradually being replaced by Combretaceae, Ilex and Schima as indicated by their continuous presence in the sediments. Probably, the absence of Pandanus pollen suggests some regional impact. Occurrence of anthropic pollen of cereals, Brassicaceae, and Plantago indicates human activity in and around the study area. The presence of Diplodia, Glomus, Meliola, Pleospora, Xylaria and other fungal hyphae strongly indicates the massive soil erosion. Judging from the present data, long term vegetation and climate shifts induced a xerophytic trend from high altitude to lowland resulting from regional and global climate change. This xerophytic trend as observed through modern palynological records was well corroborated with the present situation.

Pollen Dimorphism of Several Members of Nymphaeaceae and Nelumbonaceae: An Index of Geographical and Ecological Variation

Pollen morphology of five Nymphaea (Nymphaeaceae) species, growing in Tripura, India were analysed using Scanning Electron Microscopy. Pollen grains of Nymphaea are dimorphic (ellipsoidal and spheroidal). The exine pattern also varies among the species. The variation as reported in the present study in terms of exine pattern of the studied species suggests the feasibility of applying the data in the identification of the genus of Nymphaea. The difference in exine patterns with the earlier reports may be interpreted as reflections of genetic variations possibly due to mutational changes effected by ecological conditions. The present pollen dimorphism may be attributed by introgression of populations. The variability in pollen morphology, including size variation and morphological differences, is often associated with hybrids among angiosperm groups. The examinations of percentages of aborted grains, generally considered a good indicator of hybridity. The occurrence of monosulcate pollens in Nelumbo nucifera along with dominant tricolpate pollens may be considered as aberrant pollens because of very low percentage of occurrence of monosulcate pollens. The ecological and geographical variations in pollen morphology could be an index of the genetic impact of the environment on the plant. Thus the present difference in terms of exine pattern could be useful to separate them at varietal level.

Palynostratigraphy of the Cretaceous–lower Palaeogene sedimentary succession in the Kangerlussuaq Basin, southern East Greenland

A new palynological event biostratigraphy for the Cretaceous–lower Palaeogene succession in the Kangerlussuaq Basin, onshore southern East Greenland is presented. Sixty-three biostratigraphical marker events are recognised, based on the first and last occurrences of dinoflagellate cysts and pollen from eleven key outcrop sections through the Sorgenfri, Christian IV, Sediment Bjerge and Vandfaldsdalen Formations of the Kangerdlugssuaq and Blosseville Groups. The palynological events are correlated with published event stratigraphies and with palynological zonations from North–East Greenland, West Greenland, North America, the North Sea and the Faroe–Shetland Basin. The palynological records date the Sorgenfri Formation as middle Albian to Coniacian or ?early Santonian, the Christian IV Formation as ?late Campanian to late Maastrichtian and the Sediment Bjerge Formation as late Danian to late Selandian. The biostratigraphic ranges of dinoflagellate cysts, pollen and macrofossils around the lower to upper Maastrichtian boundary are discussed and correlated.The palynological records and recent isotopic dating results (40Ar/39Ar) of volcanic rocks indicate that the youngest sediments of the Vandfaldsdalen Formation are of Thanetian or early Ypresian age. The study documents two major hiatuses in the area: the boundary between the Sorgenfri and Christian IV Formations spans the ?upper Coniacian–Santonian and Campanian, whilst the unconformity between the Christian IV and Sediment Bjerge Formations possibly spans the uppermost Maastrichtian and the lower Danian, indicating that the Cretaceous–Palaeogene boundary is represented by a major unconformity, as recognised widely around the northern North Atlantic.

Nectar feeding by the Cape rock elephant-shrew Elephantulus edwardii (Macroscelidea) — A primarily insectivorous mammal pollinates the parasite Hyobanche atropurpurea (Orobanchaceae)

Cape rock elephant-shrews, Elephantulus edwardii (Macroscelidea) were found to be pollinators of Hyobanche atropurpurea (Orobanchaceae), a member of a holoparasitic plant genus, lacking up to now any detailed pollinator observations. The elephant-shrews were live-trapped near the plants in the Western Cape of South Africa. One animal was released in a terrarium, containing the plants. It licked nectar with its long and slender tongue while being dusted with pollen and touching the stigmas of the flowers with its nose and the fur above the snout. H. atropurpurea pollen was found in swabs of the fur around noses and snouts as well as in the faeces of captured animals. The occurrence of pollen in the faeces of the elephant-shrews is likely a result of grooming their fur as they visited the flowers without eating or damaging them. This is one of the first records of pollinating, nectar-drinking elephant-shrews, contributing to the very scarce knowledge about the behaviour of those primarily insectivorous animals, as well as small mammal pollination.

Exploring pollen percentage threshold values as an indication for the regional presence of major European trees

The aim of this investigation was to delimit pollen percentage threshold values of the major European trees as an indication of regional presence. These values can then be applied to mapping the palaeodistribution of these trees at coarse regional scales. A brief review of the most commonly applied thresholds in the published literature demonstrates the complexity of the problem and the need for this kind of study. Pollen threshold values are proposed for the presence of each of the 20 tree taxa investigated by comparing modern pollen data (2195 samples collected from a network of sites across Europe) with two sources of plant species distribution information: the modified Atlas Florae Europeae (AFE) and the map of potential natural vegetation (PNV). For 17 taxa, the modern samples frequently contain small proportions of its pollen (0.1–0.5%) regardless of the sample location with respect to the species distribution of that taxon. The best agreement between the presence of pollen and the distribution information from both AFE and the PNV map was found for Quercus, Pinus, Picea and Fagus. 12 taxa agree with AFE in as few as 9 or as many as 57% of the samples, depending upon taxon, while 13 taxa agree with the PNV map in as few as 2 or as many as 52% of the samples. Most of the pollen types reflect the AFE distribution of the parent trees better than the PNV distribution. The occurrence of pollen of Fagus, Abies, Picea and Quercus, however, relates to the tree distribution information from the PNV map as well or even better than it does to the AFE information. Based on this dataset we suggest new threshold values that minimise the presence of pollen outside the distribution, without a large reduction of the number of rightly assigned samples. We also emphasise that in heterogeneous data-sets a pollen threshold of 0.5% is a better criterion for regional presence of a tree than the often chosen continuous pollen curve.

Plant subsistence and environment at the Mesolithic site Tågerup, southern Sweden: new insights on the “Nut Age”

Pollen was analysed from a sediment sequence collected in the close vicinity of the Mesolithic settlement Tagerup, southern Sweden. Macroremains were also retrieved from numerous samples taken at the site of the archaeological excavations of Kongemose and Ertebolle settlement phases, 6700–6000 b.c. and 5500–4900 b.c. respectively. Plants and other organic remains were well preserved in the refuse layers from the settlements embedded in the gyttja. The pollen record includes no clear indications of human impact on the vegetation during the Mesolithic. The occurrence of charcoal particles and pollen of grass and herbs associated with nutrient-rich soils are contemporaneous with the Kongemose settlement. The Ertebolle settlement phase, although characterised by considerable dwelling activities less than a hundred metres from the pollen sampling site, is scarcely seen in the pollen data. Numerous finds of crushed dogwood stones from the Kongemose phase, often partly carbonised, suggest that these stones were used for the extraction of oil. Other plants found in the Kongemose refuse layers that may have been used are apples, cherries, raspberries, acorns and rowan-berries. Based on the abundance of hazelnut shells found at the studied site and in other studies of Mesolithic sites in southern Scandinavia it is proposed that these remains may testify to an important food supply rather than just use as a supplement to animal protein. It is also hypothesised that a regional decrease in hazel populations and thus hazelnut availability at the end of the Mesolithic may have motivated the adoption of Neolithic subsistence.

Surface pollen assemblages as indicators of human impact in the warm temperate hilly areas of eastern China

Investigation of 78 surface pollen samples from warm temperate hilly areas of eastern China shows that pollen assemblages in areas of different land use are significantly different. Pollen concentrations in wastelands are higher than in plantations; these, in turn, are higher than in farmlands; implying that pollen concentration decreases with increasing human impact. Arboreal pollen dominated by Pinus and Quercus is common in all samples. Herbaceous pollen percentages are higher while shrub pollen, fern spores and fern allies are lower in farmlands than in wastelands. Crop pollen is only detectable in and near farmlands; its percentages and concentrations decrease in wastelands. Cereal and Cruciferae pollen percentages average 16.7% and 6.7% in farmland respectively, but Cereal reduces to less than 3% and Cruciferae to less than 0.5% in nearby wastelands. Principle coordinates analysis and clustering analysis indicate that pollen assemblages from farmlands are distinguishable from those under other vegetation types. Occurrence of Poaceae, Chenopodiaceae, Artemisia, and Compositae pollen and Selaginella sinensis spores are closely related to human activities, and their types and frequencies indicate intensity of human impact. The spatial distribution of crops, Chenopodiaceae, and Artemisia reflects changes in both natural environments and human activities. Percentages of cereal and Cruciferae pollen, for example, increase with decreasing altitude, but decrease with increasing latitude. Understanding pollen assemblages under artificial and human-disturbed vegetation in hilly areas may aid understanding of human impacts on the plains during the early-middle Holocene.

Records of land use and medieval settlement history in Vuonninen, Dvina Karelia, Northwest Russia

AbstractAlthough the documented history of Dvina Karelia (northern Russian Karelia) does not begin until the second half of the 16th century, individual finds of prehistoric artifacts point to earlier human occupation. The present paleoecological study of the Vuonninen area is the first of its kind concerning prehistoric land use in Dvina Karelia, a large region extending from Finland to the White Sea. It is based on the pollen analysis of sediments from Lake Ylä‐Kuittijärvi near the old Karelian village of Vuonninen. In its general features, the picture of the early stages of cultivation and human activity in the village of Vuonninen is comparable to results from East Finland, the Karelian Isthmus, and the northern shores of Lake Ladoga. The first, minor indications of human influence appear in the sediments of the 4th–6th centuries A.D. in Lake Kuittijärvi. Distinct and unambiguous signs of human activity appear in the pollen record in the 12th century. This is particularly evident in the decreasing proportion of Picea, caused by the clearance of spruce forest. The beginning of cultivation is dated according to Secale pollen to the beginning of the 15th century. Intensive arable farming emerges in the early 19th century in the form of regular occurrences of Secale and Hordeum pollen. © 2010 Wiley Periodicals, Inc.

The occurrence of Ambrosia pollen in Rzeszów, Kraków and Poznań, Poland: investigation of trends and possible transport of Ambrosia pollen from Ukraine

Previous studies have shown that ragweed pollen arrives in Poland from sources in the south, in Slovakia, the Czech Republic, Hungary and Austria. It is likely that ragweed pollen also arrives from sources in the southeast (e.g. Ukraine). This hypothesis was investigated using 13 years of pollen data and back-trajectory analysis. Ambrosia pollen data were collected at three sites in Poland, Rzeszów, Kraków and Poznań. The amount of ragweed pollen recorded at Rzeszów was significantly higher than in Poznań and Kraków. This can be related to either a higher abundance of local populations of Ambrosia in south-east Poland or the proximity of Rzeszów to foreign sources of ragweed pollen. The combined results of pollen measurements and air mass trajectory calculations identified plumes of Ambrosia pollen that were recorded at Rzeszów, Kraków and Poznań on 4 and 5 September 1999 and 3 September 2002. These plumes arrived at the pollen-monitoring sites from an easterly direction, indicating sources of Ambrosia pollen in eastern Poland or Ukraine. This identifies Ukraine as a possible new source of ragweed pollen for Poland and therefore an important source area of Ambrosia pollen on the European Continent.

Palaeoecological studies at the Kaliakra area, northeastern Bulgarian Black Sea coast: 6000 years of natural and anthropogenic change

A 7.5 m sediment core from Lake Bolata, a small former coastal liman lake in northeastern Bulgaria, was analyzed for pollen and plant macrofossil content in attempt to trace the changes in the vegetation, human impact and the influence of the Black Sea during the last ca. 6,000 years. Lake Bolata started its existence when the rising Black Sea level reached the elevation of the bottom of the depression. By that time nearly all tree species were already present in this area with the exception of Carpinus orientalis. The comparison of the arrival time of oriental hornbeam at different sites along the Bulgarian Black Sea confirmed the reliability of the local radiocarbon chronology. For the period under study the vegetation of the region around the site can be described as a forest-steppe due to NAP values higher than 40% of the pollen sum. Forests on the slopes of the river canyon consisted of Quercus spp., Acer, Carpinus orientalis, Fraxinus ornus, Fagus and possibly Tilia. Riverine forests formed stands composed of Salix, Alnus, Ulmus, Fraxinus, Carpinus betulus and Vitis as a liana. The vegetation on the Cape Kaliakra plateau, bordering the canyon, was dominated by diverse herbs and most of these could be considered xerophytes. The oldest occupation period belongs to the Eneolithic, documented by the occurrences of Triticum-type pollen at 5570–5170 cal b.p. (3620–3220 b.c.). The next period of higher continuous Cerealia-type values corresponds to 3450–1830 cal b.p. (1500 b.c.–a.d. 120). The macrofossil record chiefly provides evidence about plant communities of aquatics and helophytes.

Early Cretaceous angiosperm pollen from a low-latitude succession (Araripe Basin, NE Brazil)

The radiation of flowering plants during the Cretaceous represents a marked evolutionary turnover from gymnosperm- to angiosperm-dominated ecosystems within a time span of about 30 Ma. Despite the importance of this profound ecological transformation, many aspects regarding the timing, floral composition and spatial distribution of early angiosperms are poorly documented. Here, we present a record of early angiosperm pollen from the Brazilian Araripe Basin from the late Aptian to early Albian time interval. For this study, 17 samples from 5 sedimentary sections, spanning a total of ∼ 150 m, have been investigated for their palynological content with particular attention on the occurrence of angiosperm pollen. Our results show a relatively high angiosperm pollen diversity of 70 different taxa, including numerous undescribed forms. Across the succession, angiosperm pollen accounts on average for 7% of the total palynoflora, with maximum abundances reaching 18%. Dominant taxa include monocolpate pollen of “magnoliid” or monocotyledon origin (e.g. Stellatopollis, Retimonocolpites, Pennipollis, Dichastopollenites, and Trisectoris) as well as pollen with eudicotyledon affinities (e.g. triaperturate forms like Rousea, Tricolpites, and Striatopollis). Judging from the existing evidence it appears that the diversity of the late Aptian–early Albian angiosperm palynoflora from the Araripe Basin has been underestimated. In addition, the composition of the total palynoflora shows congruent shifts in the abundance of hygrophilic ferns, Afropollis spp. and angiosperm pollen. The co-occurrence of moisture-loving ferns and early angiosperm pollen may support the hypothesis that early angiosperms evolved and diversified in moist and shady disturbed habitats near the palaeoequator.

Distribution of Microtubular Cytoskeletons and Organelle Nucleoids During Microsporogenesis in a 2n Pollen Producer of Hybrid Populus

AbstractThe distribution of microtubular cytoskeletons and organelle nucleoids during microsporogenesis in Populus simonii Carr. x P. nigra L. ‘Tongliao’ was studied by indirect immunofluorescence and 4’,6-diamidino-2- phenylindole (DAPI) staining. Our purpose was to reveal the relationship between changes in microtubule and chromosome behavior and cytokinesis and to explain the mechanism of 2n pollen production. We observed stable frequencies of 2n pollen production, ranging from 1.56% to 2.29%, between 2006 and 2008. Moreover, conjoined pollen grains were also observed. Meiotic abnormalities, including univalents, lagging chromosomes and micronuclei, were observed during microsporogenesis. Triads and dyads were also detected in meiotic products. Parallel spindles in metaphase II were unable to fuse, owing to the existence of an organelle band. Regularly, in telophase II, primary phragmoplasts were organized between sister nuclei, and secondary phragmoplasts formed between non-sister nuclei. Cell plates were initiated by centrifugal expansion of phragmoplasts and cytoplasmic infurrowing started at the junctions between the microsporocyte wall and the expanded phragmoplasts. However, a secondary phragmoplast was absent in some microsporocytes. These observations suggest that the occurrence of 2n pollen may result from the partial failure of cytokinesis caused by the absence of secondary phragmoplasts in this hybrid.

Environmental and climatic conditions at a potential Glacial refugial site of tree species near the Southern Alpine glaciers. New insights from multiproxy sedimentary studies at Lago della Costa (Euganean Hills, Northeastern Italy)

It has been hypothesized that refugia of thermophilous tree species were located in Northern Italy very close to the Alps, though, this hypothesis has yet to be tested thoroughly. In contrast to Central and Southern Italy with its relative wealth of data, only a few fragmentary records are currently available from Northern Italy for the last Glacial (Würm, Weichselian). Our new study site Lago della Costa lies adjacent to the catchment of the megafans of the Alpine forelands and the braided rivers of the Northeastern Po Plain that have so far inhibited the recovery of continuous Glacial and Late-Glacial records. We analyze pollen, plant macrofossils, charcoal and ostracods to reconstruct the vegetation, fire and lake history for the period 33,000–16,000 cal. BP. We compare our data with Glacial records from Southern Europe to discuss similarities and dissimilarities between these potential refugial areas. A comparison with independent paleoclimatic proxies allows to assess potential linkages between environmental and climatic variability. New macrofossil and pollen data at Lago della Costa unambiguously document the local persistence of boreal tree taxa such as Larix decidua and Betula tree species around the study site during the last Glacial. The regular occurrence of pollen of temperate trees in the organic lake sediments (fine-detritus calcareous gyttja) suggests that temperate taxa such as Corylus avellana, Quercus deciduous, Tilia, Ulmus, Fraxinus excelsior, Carpinus, Abies alba and Fagus sylvatica, most likely survived the Last Glacial Maximum (LGM) at favorable sites in the Euganean Hills. The percentage values of temperate trees are comparable with those from Southern Europe (e.g. Monticchio in Southern Italy). We conclude that the Euganean Hills were one of the northernmost refugial areas of temperate taxa in Europe. However, the relative and absolute abundances of pollen of temperate trees are highly variable. Pollen-inferred declines of temperate tree communities (e.g. Quercetum mixtum) and low ostracod-inferred water levels at Lago della Costa correspond to the cold Heinrich events H-2 (LGM; 23,000–19,000 cal. BP) and H-3 (around 28,000 cal. BP), as recorded in the marine sediments of the North Atlantic. Similar patterns of significant temperate tree population collapses during cold Heinrich events are recorded at southern Mediterranean sites (e.g. Monticchio and the Alboran Sea). These findings suggest close linkages between Northern Atlantic and South-Central European climates during the past Glacial.

Scanning Electron Microscopy and Synchrotron Radiation X-Ray Tomographic Microscopy of 330 Million Year Old Charcoalified Seed Fern Fertile Organs

Abundant charcoalified seed fern (pteridosperm) pollen organs and ovules have been recovered from Late Viséan (Mississippian 330 Ma) limestones from Kingswood, Fife, Scotland. To overcome limitations of data collection from these tiny, sometimes unique, fossils, we have combined low vacuum scanning electron microscopy on uncoated specimens with backscatter detector and synchrotron radiation X-ray tomographic microscopy utilizing the Materials Science and TOMCAT beamlines at the Swiss Light Source of the Paul Scherrer Institut. In combination these techniques improve upon traditional cellulose acetate peel sectioning because they enable study of external morphology and internal anatomy in multiple planes of section on a single specimen that is retained intact. The pollen organ Melissiotheca shows a basal parenchymatous cushion bearing more than 100 sporangia on the distal face. Digital sections show the occurrence of pollen in some sporangia. The described ovule is new and has eight integumentary lobes that are covered in spirally arranged glandular hairs. Virtual longitudinal sections reveal the lobes are free above the pollen chamber. Results are applied in taxonomy and will subsequently contribute to our understanding of the former diversity and evolution of ovules, seeds, and pollen organs in the seed ferns, the first seed-bearing plants to conquer the land.