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"Palynology"
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Systematic position of miyakea integrifolia miyabe & tatew. In the infrageneric classification of pulsatilla (ranunculaceae): palynological challenges
Abstract not available.
Bangladesh J. Plant Taxon. 31(1): 187-195, 2024 (June)
Journal Article
Systematic importance of morphological features of pollen grains of species from Erica
The Erica genus has as yet not been investigated satisfactorily in terms of palynology. Its complicated taxonomic system, large number of species, as well as its extensive but disrupted range of occurrence, all contribute to the fact that few researchers have undertaken investigations of this species. It was assumed that the research results would be representative thanks to a complex comparative analysis of all diagnostical, morphological pollen features performed on properly selected plant material, representing the most important distinguished intrageneric taxons at the present time (45 species from all five subgenera and 22 sections), both discriminated pollen dispersal units (tetrads and monads) as well as the main centres of genus occurrence and diversification (species from Europe, the Republic of South Africa (RSA) and Madagascar). The study revealed that the diagnostic features of the pollen grains studied were: pollen dispersal unit, exine ornamentation, P/E ratio, tetrad diameter (D) and length of polar axis (P). On the basis of these traits, 14 Erica species (six creating monads and eight-tetrads) were distinguished which, in the case of pollen features, constitutes a significant number. Other heaths created small groups, usually containing two or three species, but up to seven species. The present study, based on the highest number of Erica species (45) analysed so far, corroborated the view that an examination of palynological features may assist in clarifying classification systems for the large and taxonomically very difficult Erica genus, in particular, at the level of the subgenus and section, but also at species level. The results obtained indicate the need to continue palynological investigations on the Erica genus.
Journal Article
Improving the taxonomy of fossil pollen using convolutional neural networks and superresolution microscopy
Taxonomic resolution is a major challenge in palynology, largely limiting the ecological and evolutionary interpretations possible with deep-time fossil pollen data. We present an approach for fossil pollen analysis that uses optical superresolution microscopy and machine learning to create a quantitative and higher throughput workflow for producing palynological identifications and hypotheses of biological affinity. We developed three convolutional neural network (CNN) classification models: maximum projection (MPM), multislice (MSM), and fused (FM). We trained the models on the pollen of 16 genera of the legume tribe Amherstieae, and then used these models to constrain the biological classifications of 48 fossil Striatopollis specimens from the Paleocene, Eocene, and Miocene of western Africa and northern South America. All models achieved average accuracies of 83 to 90% in the classification of the extant genera, and the majority of fossil identifications (86%) showed consensus among at least two of the three models. Our fossil identifications support the paleobiogeographic hypothesis that Amherstieae originated in Paleocene Africa and dispersed to South America during the Paleocene-Eocene Thermal Maximum (56 Ma). They also raise the possibility that at least three Amherstieae genera (Crudia, Berlinia, and Anthonotha) may have diverged earlier in the Cenozoic than predicted by molecular phylogenies.
Journal Article
Assessment of palynological spectrum of air in Kazan
This article presents the results of a palynological air monitoring study in Kazan during the period of plant dusting from 2019 to 2022. The aeropalynological spectrum was assessed using a Lanzoni pollen trap. The data obtained during the monitoring demonstrates a rich spore-pollen composition in the air. Twenty-five different plant taxa, as well as two fungal taxa, were identified.
Betula
and
Poaceae
have been identified as dominant taxa. The variability in pollen concentrations confirms the need for timely information for the pollen-sensitive population.
Journal Article
Challenges and opportunities in Quaternary palynology
Quaternary palynology plays a pivotal role in investigating global climate change and various other research fields, serving as an essential tool for the quantitative analysis of paleoenvironment changes. However, due to the vast diversity of terrestrial ecosystems and intricate interactions between vegetation, climate, and human activities, further advancements are required in the following aspects within this discipline. (1) The accuracy of classification in pollen morphology and fossil pollen identification needs improvement, particularly at the species level. This represents a significant challenge in present Quaternary palynology. Computer-aided intelligent recognition holds promise as a solution for species identification based on more detail pollen morphology. (2) Most pollen-based vegetation and climate reconstructions overlook the significance of bare ground. Neglecting bare ground can lead to substantial inaccuracies when quantitatively reconstructing past vegetation and climate. (3) While pollen records provide reliable information on paleoclimate changes, current quantitative climate reconstruction models heavily rely on modern pollen datasets derived from present-day vegetation disturbed more or less by human activities. This introduces bias and uncertainties into paleoclimate reconstruction. (4) Although pollen can serve as an indicator of human activities, accurately quantifying the intensity of human influence remains challenging. Improving accurate identification of crop pollen, reconstructing reliable land cover/use data, and integrating multidisciplinary data may enhance the identification and quantification of signals related to human activity in pollen records.
Journal Article
Fifty years of Quaternary palynology in the Tibetan Plateau
Quaternary palynology in the Tibetan Plateau (TP) was initiated in the 1960s to meet the needs of economic development in western China. Pollen analysis was conducted for the first time on a 200-m long core of Quaternary lacustrine sediments taken from the main body of the TP in order to study pollen assemblages as well as vegetation and climate changes of glacial (cold)/interglacial (warm) periods. Pollen analysis of alpine snow and ice began at the first scientific expedition to the TP in the 1970s. After the 1980s, a series of international collaborative programs were carried out under Sino-French, Sino-German, Sino-Australian, and Sino-American cooperation, marking the integration of Chinese Quaternary palynology society with the international community. New methods for Quaternary palynology were gradually promoted and applied, changing the vegetational and climatic interpretation of Quaternary palynology from qualitative to quantitative. Since the 1990s, many palynologists have carried out extensive Quaternary palynological studies on fossil pollen sites of more than 60 lakes/sections and alpine glaciers in the TP to discuss the spatiotemporal vegetation changes and climatic and environmental evolution of the TP since the Pleistocene. Over the past half-century, Quaternary palynology in the TP has contributed to the establishment of the Chinese Quaternary pollen database and the study of vegetation and climate evolution since the Last Glacial Maximum (LGM) in the TP. Currently available pollen records revealed the spatial and temporal distribution of vegetation in the TP since the LGM, exhibiting expansions and shrinkages of forest, meadow, grassland and desert in different periods such as the LGM, the last deglaciation, and Holocene optimum period. The paleomonsoon reflected by paleovegetation since the LGM has undergone the changes of weak-strengthening-strong-weakening but still active-shrinking, which is mainly affected by solar insolation.
Journal Article
How deep is the conflict between molecular and fossil evidence on the age of angiosperms?
Summary
The timing of the origin of angiosperms is a hotly debated topic in plant evolution. Molecular dating analyses that consistently retrieve pre‐Cretaceous ages for crown‐group angiosperms have eroded confidence in the fossil record, which indicates a radiation and possibly also origin in the Early Cretaceous. Here, we evaluate paleobotanical evidence on the age of the angiosperms, showing how fossils provide crucial data for clarifying the situation. Pollen floras document a Northern Gondwanan appearance of monosulcate angiosperms in the Valanginian and subsequent poleward spread of monosulcates and tricolpate eudicots, accelerating in the Albian. The sequence of pollen types agrees with molecular phylogenetic inferences on the course of pollen evolution, but it conflicts strongly with Triassic and early Jurassic molecular ages, and the discrepancy is difficult to explain by geographic or taphonomic biases. Critical scrutiny shows that supposed pre‐Cretaceous angiosperms either represent other plant groups or lack features that might confidently assign them to the angiosperms. However, the record may allow the Late Jurassic existence of ecologically restricted angiosperms, like those seen in the basal ANITA grade. Finally, we examine recently recognized biases in molecular dating and argue that a thoughtful integration of fossil and molecular evidence could help resolve these conflicts.
Journal Article
Age and pattern of the southern high-latitude continental end-Permian extinction constrained by multiproxy analysis
Past studies of the end-Permian extinction (EPE), the largest biotic crisis of the Phanerozoic, have not resolved the timing of events in southern high-latitudes. Here we use palynology coupled with high-precision CA-ID-TIMS dating of euhedral zircons from continental sequences of the Sydney Basin, Australia, to show that the collapse of the austral Permian
Glossopteris
flora occurred prior to 252.3 Ma (~370 kyrs before the main marine extinction). Weathering proxies indicate that floristic changes occurred during a brief climate perturbation in a regional alluvial landscape that otherwise experienced insubstantial change in fluvial style, insignificant reorganization of the depositional surface, and no abrupt aridification. Palaeoclimate modelling suggests a moderate shift to warmer summer temperatures and amplified seasonality in temperature across the EPE, and warmer and wetter conditions for all seasons into the Early Triassic. The terrestrial EPE and a succeeding peak in Ni concentration in the Sydney Basin correlate, respectively, to the onset of the primary extrusive and intrusive phases of the Siberian Traps Large Igneous Province.
The continental record of the end Permian mass extinction is limited, especially from high paleolatitudes. Here, Fielding et al. report a multi-proxy Permo-Triassic record from Australia, resolving the timing of local terrestrial plant extinction and the relationship with environmental changes.
Journal Article
Borneo and Indochina are Major Evolutionary Hotspots for Southeast Asian Biodiversity
Tropical Southeast (SE) Asia harbors extraordinary species richness and in its entirety comprises four of the Earth's 34 biodiversity hotspots. Here, we examine the assembly of the SE Asian biota through time and space. We conduct meta-analyses of geological, climatic, and biological (including 61 phylogenetic) data sets to test which areas have been the sources of long-term biological diversity in SE Asia, particularly in the pre-Miocene, Miocene, and Plio-Pleistocene, and whether the respective biota have been dominated by in situ diversification, immigration and/or emigration, or equilibrium dynamics. We identify Borneo and Indochina, in particular, as major \"evolutionary hotspots\" for a diverse range of fauna and flora. Although most of the region's biodiversity is a result of both the accumulation of immigrants and in situ diversification, within-area diversification and subsequent emigration have been the predominant signals characterizing Indochina and Borneo's biota since at least the early Miocene. In contrast, colonization events are comparatively rare from younger volcanically active emergent islands such as Java, which show increased levels of immigration events. Few dispersal events were observed across the major biogeographic barrier of Wallace's Line. Accelerated efforts to conserve Borneo's flora and fauna in particular, currently housing the highest levels of SE Asian plant and mammal species richness, are critically required.
Journal Article