A neotaphonomic experiment in pollen oxidation and its implications for archaeopalynology

Oxidation is considered to be a major taphonomic process involved in differential pollen preservation. An experimental protocol has been developed in the laboratory to test the impact of oxidation on pollen concentrations. Seven modern pollen taxa were selected among common trees, shrubs and herbaceous plants from the European flora, with regard to their typical pollen morphology (Pinus, Alnus, deciduous Quercus, Cichorioideae, Caryophyllaceae, Ericaceae and Poaceae). An aqueous solution of potassium permanganate (KMnO₄) was used to oxidise the pollen grains. The impact of oxidation was measured as a function of increasing oxidation intensity and increasing exposure time. For each taxon, the pollen concentration (grains µl⁻¹) was measured following each oxidation stage. The results show that all pollen taxa are affected by oxidation. Both low oxidant concentrations and short oxidation exposure times led to a fast decrease in pollen concentrations. The thickness of the exine and a specific morphology appear to be the deciding factors controlling the ability to withstand oxidation. A simulation of the impact of oxidation was performed on two model pollen spectra simulating a forested and an open environment. Significant differences were recorded between the initial and final pollen rates. The AP/NAP ratio is modified to a greater extent in the spectrum associated with the open environment. However, over-representation of a specific taxon in a pollen spectrum cannot be attributed to the impact of oxidation alone. For instance, when Cichorioideae are recorded with high frequencies in pollen analyses carried out in an archaeological context, oxidation should not be regarded as the only taphonomic process responsible for this over-representation. The differential conservation of pollen is a complex process in which oxidation represents but one of a variety of interacting taphonomic factors (such as pollen transport, bacterial activity, temperature, pH, hygrometry).     

Biflavonoids from the seed testa of cycadales

Biflavonoid patterns from ethanolic extracts of the brightly coloured testa of eight species of Cycadales have been determined. Species from the genus Macrozamia are characterized by the occurrence of cupressuflavone- and amentoflavone-based patterns, while the Cycas species contain only amentoflavone-based patterns. The other species from the genera Encephalartos, Lepidozamia, and Zamia contain a very minor or no detectable biflavonoid component. This is the first report of the occurrence of cupressuflavone in the Cycadales.     

Vegetation reconstruction on the basis of pollen in Late Pleistocene hyena coprolites from San Teodoro Cave (Sicily, Italy)

Vegetation reconstruction based on pollen from coprolites of extinct spotted hyena (Crocuta crocuta spelaea, Goldfuss 1832) recovered from excavations carried out in 1998 at San Teodoro Cave (Sicily, Italy) supports previous indications of pre-Late Glacial conditions. Eight of the twelve coprolites analysed contained well-preserved pollen grains. There is a general similarity between the pollen contents from the coprolites but they show variability. They suggest a main vegetation type dominated by steppic taxa (Poaceae, Artemisia, Ephedra, Chenopodiaceae and Asteraceae) but also including arboreal taxa (Pinus and Cupressaceae). Low percentages of pollen of mesophilous woody taxa (Quercus, Betula, Abies, Alnus, Pistacia, among others) are noticeable, suggesting the existence of nearby refugia for temperate and Mediterranean vegetation. A reconstruction of the landscape, using the coprolite pollen record and other pollen records from Sicily and south Italy, shows the predominance, during the pre-Late Glacial, of a wooded steppe biome, with elements representing a variety of local environmental conditions.     

A comparative study of cycad mucilages

The patterns of monosaccharide distribution of the mucilages of Cycadales are characteristic at the generic level. Arabinose, fucose, galactose, mannose, rhamnose and methylrhamnose were identified in the hydrolysed mucilage of Bowenia, Ceratozamia, Cycas, Dioon, Encephalartos, Lepidozamia, Macrozamia, Microcycas and Zamia. Stangeria contains no rhamnose and methylrhamnose, and Ceratozamia contains galactose only in traces. American genera may easily be distinguished from the others by means of their different monosaccharide composition. Lepidozamia appears to be well separated from Macrozamia.     

四川螺髻山表土和化石孢粉揭示的环境生态意义

通过四川螺髻山（1984、2017年）表土和化石孢粉与植被的关系分析发现：孢粉组合中木本植物含量（91.0%）占绝对优势,松属、冷杉属、青冈属、常绿栎类、落叶栎类、桤木属、杜鹃花科、禾本科和蒿属为主要花粉类型;人工次生林花粉组合能很好地反映母体植被的群落特征,并可指示优势种的存在和人类活动痕迹;针阔混交林花粉组合能较好地反映群落整体特征,花粉类型能与母体植被中优势种较好地对应;常绿阔叶林、针叶林和灌丛草甸的花粉组合难以反映母体植被的群落特征。DCA表明,花粉谱的百分含量,能较好地区分人工扰动植被和天然植被,但人工次生林、常绿阔叶林和针阔混交林之间以及针叶林和灌丛草甸之间未能区分。30年前后表土孢粉组合变化明显,1984年样品以松属、青冈属和桤木属等花粉为主,而2017年采样分析中松属、桤木属花粉占绝对优势。随着人类活动的加强,部分地区松树和桤木大面积飞播或种植,表土孢粉组合对当地植被指示意义与扰动强度呈负相关关系。现生植被与表土孢粉组合的差异能为恢复古植被和古环境提供参考,但原生植被已经被破坏地区的孢粉图谱,就很难作为重建历史时期植被的根据。本研究可以为亚热带山地利用孢粉学恢复第四纪时期植被与气候,探讨人类活动与环境的关系提供理论依据和实践参考。     

Pollen stratigraphy of coal-bearing deposits in the Neogene Jidong Basin,Heilongjiang Province,NE China: New insights on palaeoenvironment and age

The palaeoenvironment and age of coal-bearing lacustrine deposits in the Jidong Basin, Heilongjiang Province, is poorly understood. New pollen data from the Yongqing Formation and the overlying lower part of the Daqingshan Formation recovered in borehole 91-205 revealed a rich and diverse palynoflora representing approximately 70 taxa at the genus/family level. Of these taxa, Ulmus, Quercus, Carya, Liquidambar, Pinus, Tilia, Fagus, and Alnus are the main woody elements; these occur together with numerous pteridophytes, subordinate herbs, and rare algae and acritarchs. Abundant woody taxa suggest a mixed deciduous/conifer forest in the region in association with local shrubs, herbs and algal communities. Some of the pollen types, especially those of climate sensitive genera such as Ulmus, Carya, Liquidambar and Fagus, vary considerably in relative abundances, suggesting climate variability. The reflected climate shows an overall trend towards cooling or deterioration which is largely in agreement with global climate change during the Neogene.Comparisons of the pollen record with representative datasets from neighbouring areas, together with the appearance of the highly-evolved genus Artemisia, suggest that the Yongqing Formation and the lower part of the Daqingshan Formation are of Miocene age.     

Synchronized inter‐annual fluctuation of flowering intensity affects the exposure to allergenic tree pollen in North Europe

Many anemophilous, early‐flowering tree genera include allergy plants of world‐wide significance. We studied the synchronisation of high and low pollen years in the genera Betula, Alnus, Corylus, Salix and Populus and the cumulative effects that an increasing number of taxa has on the number of days of exposure to different levels of allergenic pollen in North Europe. The proximal causes of the inter‐annual variations of airborne pollen loads were analysed with a multiple regression analysis. The annual fluctuations of airborne pollen sums were compared between genera and found to be positively correlated among all combinations of genera at the three study sites. Most correlations were statistically significant (p<0.05). The comparison between Betula and Alnus is discussed first. Betula pollen was clearly the most abundant airborne pollen type. The presence of Alnus pollen, however, significantly increased the predisposal to allergenic pollen. At all sites, the number of days per year when the Betula and Alnus pollen counts together exceeded 10 and 100?grains m^?3 of air, was found to be greater than the number of days when the Betula pollen counts alone exceeded 10 and 100?m^?3 of air. The difference was statistically significant. In Kuopio, the difference was found to be statistically significant even for grains per 1?000?m^?3 of air of Betula and Alnus together compared with the same count of Betula pollen alone. Betula, Alnus and Corylus belong to the order Fagales and have cross‐reacting main allergens. The flowering of Alder and Corylus culminate at the same time, two to four weeks earlier than that of Betula. Due to synchronization of high and low years and the mostly non‐overlapping flowering seasons, the time of exposure to pollen may be very long during the high years. Furthermore, Alnus and Corylus pollen may prime allergic people before the onset of the Betula season.     

Diurnal patterns of airborne pollen concentration of the selected tree and herb taxa in Gdańsk (northern Poland)

The diurnal variation of airborne pollen concentrations of Alnus, Betula, Pinus, Poaceae, Urtica and Artemisia was examined at the sampling station in Gdańsk, northern Poland. Diurnal patterns of Alnus and Pinus pollen show distinctly lower values and low frequency of diurnal maxima between midnight and late morning and a clear rise of pollen counts at around noon. The rather high values remain during the afternoon and evening. The Betula pollen counts are almost evenly distributed along day and night and diurnal maxima appear in similar frequency at any time of day. Pollen concentrations of Poaceae increase at about 9.00 hours and remain high till late evening. Diurnal patterns of Urtica and Artemisia show very clear variation with high peaks at around 9.00 hours (Artemisia) and 13.00 hours (Urtica). The comparison of the data from Gdańsk with the data from other aerobiological stations shows very similar general features in the diurnal patterns irrespective the region or the local situation.     

Haustorial Role of Pollen Tubes

In angiosperms, the pollen tube is siphonogamous and its mainfunction is to carry the male gametes for double fertilization.In some taxa, as in Cucurbitaceae, the tube branches after enteringthe ovule, prior to fertilization. The tube may even swell andform a bulla. During post-fertilization development of the ovule,a portion of the tube may persist in the micropyle, or in theembryo sac, or in both, sometimes even in the micropyle of themature seed. Haustorial function has been presumed in a numberof taxa. In Grevillea, following fertilization, the pollen tube branchesat the micropyle, and the branches grow intercellularly intothe ovarian tissue where further branching occurs. A haustorialrole of the pollen tube is presumed from circumstantial evidence.In gymnosperms (for example, Cycas, Zamia and Ginkgo) the pollentube is nonsiphonogamous, arises from the distal (upper) poleof pollen grain, and grows laterally in the apical region ofthe nucellus. The tube branches in Cycas and Ginkgo but remainsunbranched in Zamia. These pollen tube branches are enucleate,and are not concerned with the transport of male gametes forfertilization. However, the haustorial role has been well documented.In Podocarpus, the pollen tube is siphonogamous and arises fromthe proximal (lower) pole of pollen grain. After traversingthe nucellus, the tube forms a bulla at the point of contactwith the female gametophyte, and several branches originatefrom the bulla. The pollen tube branches grow along the innersurface of the nucellus and the outer surface of the femalegametophyte. The haustorial role of the pollen tube branchesis uncertain. Procedures for convincingly demonstrating thehaustorial role of pollen tubes are discussed. Angiosperms, gymnosperms, pollen tube, bulla, fertilization, haustorial role     

Pollen calendar for Vigo, North-West Spain (1995)

This is the first data from a pollen survey in Vigo, an Atlantic city in northwest Spain. The pollen calendar for Vigo is presented, as well as the pollination period for the nine most important allergenic plants. Through 1995, 30 083 pollen grains belonging to 52 taxa, were recorded using the Lanzoni VPPS 2000 volumetric spore-trap. The most relevant taxa found were: Urticaceae,Pinus, Poaceae andQuercus (75% of the total pollen),Betula, Castanea, Cupressaceae, Chenopodiaceae, Ericaceae, Myrtaceae,Olea, Plantago, Platanus andRumex (21%), and the final 4% was distributed mainly among pollen types, such as:Corylus, Alnus, Fabaceae, Compositae,Artemisia andCedrus. Of the total annual pollen count, 56% was found in March and April. Another, secondary peak was recorded in June corresponding to the flowering period of herbaceous species. The high pollen total of Urticaceae (7625 grains, 25% of the total) should be highlighted. The percentages ofOlea europaea (565 grains) should be noted as well, taking into account its geographical distribution.     

Pollen analysis from two littoral marshes (Bourdim and Garaat El-Ouez) in the El-Kala wet complex (North-East Algeria). Lateglacial and Holocene history of Algerian vegetation

The study of two pollen sequences from El-Kala marshes allowed the reconstruction of the regional vegetation history supported by eight radiocarbon dates. Pollen assemblages from Bourdim site were dominated by local input of Alnus and Salix, while regional vegetation was characterized by scattered Quercus suber forests with a well-developed Erica arborea matorral. While the vegetation dynamics recorded at Bourdim is recent (Late Holocene), the majority of the pollen diagram from Garaat El-Ouez is contemporaneous to the Late Pleniglacial and is characterized by open woodlands with Pinus, Poaceae and several heliophilous herbs. The significant values of Cedrus pollen identified in this period indicate that the region of El-Kala most probably played the role of a refugium for this tree.     

Regional distribution of Ginkgo biloba-induced c-Fos immunoreactivity

A growing literature supports the notion that Ginkgo biloba has cognitive enhancing and anxiolytic properties; however, its effects on neuronal populations have yet to be characterized. The present study used c-Fos immunoreactivity (Fos-IR) to characterize functional activity in selected brain regions following administration of a standardized Ginkgo biloba extract. Because Ginkgo is typically consumed orally, Exp 1 sought to identify patterns of neural activity induced by oral administration. To ensure that the alterations in functional neural activity observed in Exp 1 were not simply due to novel gustatory experience, Exp 2 characterized patterns of Fos-IR following intraperitoneal administration of Ginkgo. Rats were habituated to handling and experimental conditions. In Exp 1, rats self-administered 150 mg/kg Ginkgo or vehicle alone (strawberry jam) orally. In Exp 2, rats were injected with Ginkgo (2.5 or 25 mg/kg, i.p.) or vehicle (0.3% gum Arabic). Animals were anaesthetized and perfused transcardially. Brains were sectioned, immunostained using a c-Fos antibody, then the number of labelled cells was quantified microscopically in selected brain regions. In both experiments Ginkgo increased Fos-IR in numerous brain regions including the insular cortex and amygdala. Intraperitoneal administration induced Fos-IR in some additional regions including the nucleus accumbens and dentate gyrus. Results provide important preliminary data serving to identify several candidate neural sites involved in the cognitive enhancing and anxiolytic effects of Ginkgo biloba.     

Changes in the Mediterranean pine forest: pollination patterns and annual trends of airborne pollen

In some areas, forests are being affected in diverse aspects such as structure, composition and biodiversity showing an increase or a decrease in the growth rates. Pinus is one of the most dominant genera in the forests of the Northern Hemisphere. This study analyzes the pine pollination patterns in 30 locations of Spain with an average of 21-year dataset. The aim is to evaluate possible changes in flowering intensity as well as in annual pollen production trends, according to the airborne pollen patterns. Annual Pollen Indices show three threshold values: (1) over 4000 grains per year in Catalonia, the Central System Mountains and Ourense (Galicia), (2) between 4000 and 1000 grains in central-south Spain and in the Balearic Islands, and (3) under 1000 in eastern Spain, Cartagena and the Canary Islands. Airborne pollen patterns were also influenced by Pinus species: The species located in the littoral and low land areas pollinated in the first pollination phase, from February to April, and the mountain pine species did in the second one, from April to June. The statistical analyses reveal increasing significant trends in 12 sites and significant decreasing trends in two. The Pinus flowering intensity is showing an earlier start and a delay in the end of the pollination period, thus a longer period of pollen in the air. This study suggests that the aerobiological monitoring is an interesting bio-indicator of changes happening in Pinus landscapes, and therefore explains the vulnerability of this genus in Spain.     

The significance of pollen signal in present-day marine terrigenous sediments: The example of the Gulf of Lions (western Mediterranean Sea)

Terrigenous marine and continental sediments constitute pollen reservoirs able to fulfil the lack of Pleistocene data extracted from autochtonous lacustrine sediments for palaeovegetation reconstructions. Nevertheless, it is essential to constrain the signification of the pollen signal in such still under-exploited sediments. This article introduces a study carried out on the shelf of the Gulf of Lions. It aims at (1) highlighting the transport of pollen grains and the signification of the record in that area as well as at (2) discussing the pollen transport in various sedimentary contexts. The present study was carried out on surface water of the Rhone River, sea water and surface sediments of the shelf of the Gulf of Lions. The pollen content of the Rhone River and of its plume is in agreement with the season of sampling. On the contrary, the other samples of sea water did not contain any pollen grain. The samples from the surface sediments of the shelf are very rich in pollen grains and evidence the absence of sorting by currents except for Pinus. Indeed, its relative abundance increases when the fluvial impact decreases. The pollen signal (except Pinus) records the phytogeographic changes linked to the different drainage basins. The riparian woodland is over-represented at the Rhone River mouth. In front of the Pyreneo-languedocian rivers, Mediterranean xerophytes pollen grains are more abundant. From these results and from others taken in the literature, a model of pollen transport is built: all thin terrigenous sediments contain pollen grains essentially transported by rivers while autochthonous sediments (i.e., found in closed lakes or marine pelagic sediments) contain pollen grains brought by wind. Small closed lakes (or peat bogs) pollen spectra document local floras while those from pelagic marine sediments document floras from several hundred square kilometres.     

Comparison of Alnus,Corylus, Betula pollen seasons in Riga,Moscow and Vilnius

Research characterizes differences and similarities of the seasonal behaviour of Alnus, Betula, Corylus pollen in Riga, Moscow and Vilnius. An important uniting factor dealing with the research is that on the selected territories in spring there are abundance of Alnus, Corylus and Betula airborne pollen. The study is based on the 2004–2011 atmospheric pollen records. Differences and similarities of the analysed territories include the following: (1) the beginning of the Alnus and Corylus pollen season usually coincided in Riga and Vilnius, whereas significantly differed between Riga and Moscow; (2) no significant differences among separate stations have been estimated concerning the beginning of the Betula pollen season; (3) Moscow differed by the shortest period of pollen season, independently of the pollen type; (4) the biennial cycle of Betula pollen is characteristic to Riga only; (5) in the spectrum of spring plants’ pollen, Corylus pollen was found in the least amount (10–23 pgm^?3 per day on the average); (6) average concentration of Betula pollen per day significantly differed in all locations of the survey, in Moscow, the concentration (853 pgm^?3) was twice higher that in Riga and Vilnius; (7) Alnus, Corylus and Betula pollen seasons overlap each other in all locations surveyed, thus creating additional load of pollen; (8) in each of the stations, there were 13–15 days when concentration of Betula pollen exceeded 100 pgm^?3.     

Palynological record of climate change during the last deglaciation from the Song Hong (Red River) delta, Vietnam

The palynological sequence from core ND-1 on the Song Hong delta in the northern Vietnam reveals the climate change during the last deglaciation. The identified pollen in the core is dominated by Castanopsis (Lithocarpus), Elaeocarpus, Ficus, Piperaceae and Quercus. High percentages of temperate taxa including the conifers Dacrydium, Podocarpus, Pinus, Cupressaceae, Txodiaceae and Cryptomeria, and broad-leaved taxa of Carpinus, Alnus, Juglans, Carya, Ulmus, Fagus, Ilex, Castanea, Quercus, which have a mainly upland distribution, is possibly associated with a lowering of the montane vegetation boundary. On the other hand, intensified river influence can also result in an increase in the temperate allochthonous taxa. After analyzing the magnitude of river influence on pollen assemblages during the sedimentary environment evolution, we extracted the climate information and used this to reconstruct climate change during the last deglaciation. A cooler climate during 14.5-10.9 cal. kyr BP than at present is indicated by higher percentage of temperate types than at present under a similar river influence on the floodplain. The Younger Dryas cooling event is recognized by widely developed grasslands between 12.9 and 11.6 cal. kyr BP, adding to the evidences for this period from both terrestrial and marine records in regions influenced by the East Asian monsoon. Two other cooling periods, 9.4-9.0 cal. kyr BP and 6.5-5.2 cal. kyr BP, are indicated by increases of temperate pollen taxa such as Cryptomeria, Alnus, Quercus, and Castanea.     

Phylogeny of the cycads based on multiple single-copy nuclear genes: congruence of concatenated parsimony,likelihood and species tree inference methods

Background and aims

Despite a recent new classification, a stable phylogeny for the cycads has been elusive, particularly regarding resolution of Bowenia, Stangeria and Dioon. In this study, five single-copy nuclear genes (SCNGs) are applied to the phylogeny of the order Cycadales. The specific aim is to evaluate several gene tree–species tree reconciliation approaches for developing an accurate phylogeny of the order, to contrast them with concatenated parsimony analysis and to resolve the erstwhile problematic phylogenetic position of these three genera.

Methods

DNA sequences of five SCNGs were obtained for 20 cycad species representing all ten genera of Cycadales. These were analysed with parsimony, maximum likelihood (ML) and three Bayesian methods of gene tree–species tree reconciliation, using Cycas as the outgroup. A calibrated date estimation was developed with Bayesian methods, and biogeographic analysis was also conducted.

Key Results

Concatenated parsimony, ML and three species tree inference methods resolve exactly the same tree topology with high support at most nodes. Dioon and Bowenia are the first and second branches of Cycadales after Cycas, respectively, followed by an encephalartoid clade (Macrozamia–Lepidozamia–Encephalartos), which is sister to a zamioid clade, of which Ceratozamia is the first branch, and in which Stangeria is sister to Microcycas and Zamia.

Conclusions

A single, well-supported phylogenetic hypothesis of the generic relationships of the Cycadales is presented. However, massive extinction events inferred from the fossil record that eliminated broader ancestral distributions within Zamiaceae compromise accurate optimization of ancestral biogeographical areas for that hypothesis. While major lineages of Cycadales are ancient, crown ages of all modern genera are no older than 12 million years, supporting a recent hypothesis of mostly Miocene radiations. This phylogeny can contribute to an accurate infrafamilial classification of Zamiaceae.     

Enzymic oxidation of linolenate by Ginkgo leaves: Fractionation and characterization of active fractions

An aqueous extract of defatted, macerated leaves of Ginkgo biloba L. catalysed the oxidation of linolenate. Extracts prepared from quickly frozen Ginkgo leaves had almost the same activity as the extract from fresh leaves but no trans-2-hexenal was formed. The activity was surprisingly stable at 100° and to acids. However, at pH 12 a marked loss of activity was observed, particularly when the soln was heated, and Pronase, also destroyed most of the activity.     

Flowering phenology and airborne pollen grains of chosen tree taxa in Rzeszów (SE Poland)

The aim of the study was to compare the courseof flowering and the occurrence of Alnus,Corylus and Betula pollen grains inthe air in 1999–2001. In 2000 and 2001 birchesflowered in a typical way – the floweringperiod was short and intense and that periodhad the highest concentration of pollen. Bothyears had no rainfall then and the temperaturewas high, which caused intense flowering ofbirches over a large area. In 1999 and 2000most of the Alnus and Coryluspollen was recorded at the end or after theirflowering period. At that time the weather wasunstable (as is usual in February and March).Pollen must have been transported fromelsewhere. Wind analysis showed that the mainsources of Corylus pollen must have beenin the south, and of Alnus in the southand west. In the southern margin of Poland thevegetative period begins later due to a colderclimate.