搜索结果：million-year-old

Present-day angiosperm plants produce a plethora of metabolites including pigments that serve for important functions such as photosynthesis, protection against light, attraction of pollinators, and defense against microbes and herbivores. However, little is known about phytochemical constituents of ancient angiosperms, their distribution in the fossil record, their stability in deep time, and diagenesis. Outstanding preservation of ancient angiosperms, including exceptional color preservation, has been reported, but chemical analyses of such valuable specimens are limited by the rarity of the fossil material and the small amounts of potentially preserved metabolites. Here we use highly sensitive targeted liquid chromatography-tandem mass spectrometry in multiple reaction monitoring mode to screen for nanogram quantities of intact ancient phytochemical metabolites and their products in exceptionally well-preserved, about 45-Ma-old leaves from the Eocene Geiseltal fossil Lagerstätte, Germany. We show that diverse chlorophyll derivatives and degradation products as well as polyphenolic pigments are preserved in green to yellow colored angiosperm leaves and the brown coal matrix from Geiseltal. Most interesting is the fossil occurrence of the "unstable" green chlorophyll derivative dihydro-132,173-cyclopheophorbide a-enol, since cyclopheophorbide-enols are otherwise known as unique non-fluorescent chlorophyll catabolites of microorganisms in modern aquatic environments. The monopyrrole hematinic acid is interpreted as a stable product of chlorophyll catabolism via linear tetrapyrroles. Moreover, polyphenolic compounds in the fossil angiosperms are represented by the flavonoid pigments apigenin and luteolin. Our results demonstrate the potential of paleometabolomic-like screening of individual plant fossils to trace the fate of phytochemical constituents and to understand the processes of fossilization at the molecular level.

Mycorrhizal associations between fungi and plants are a fundamental aspect of terrestrial ecosystems. Mycorrhizas occur in c. 85% of extant plants, yet their geological record remains sparse. Rare fossil evidence from early terrestrial environments offers crucial insights into these ancient symbioses, but visualizing fossil fungi at the microscale within plant tissues is challenging. Here, we combine confocal laser scanning microscopy and fluorescence lifetime imaging microscopy (FLIM) to investigate a newly identified fungus and cellular structures of a 407-Myr-old plant from the Windyfield Chert, a stratigraphically distinct fossiliferous unit from Rhynie (Scotland). We also applied Raman spectroscopy to investigate the carbon framework of both fungal and plant tissues. This integrative approach revealed fungal structures in unprecedented detail. The fungus, Rugososporomyces lavoisierae gen. nov., sp. nov., exhibits features resembling extant Glomeromycotina arbuscular mycorrhizal fungi. This is the first record of mycorrhizas from the Windyfield Chert. FLIM further distinguished features at the subcellular level, while Raman spectroscopy showed that fungal arbuscules and vesicles of the plant water-conducting cells underwent geological alterations, resulting in a similar chemical composition. These findings expand our understanding of ancient and extremely rare plant-fungal symbioses and highlight the potential of confocal-FLIM for advancing palaeobotanical research. Les associations mycorhiziennes entre les plantes et les champignons sont omniprésentes dans les écosystèmes terrestres actuels. En effet, elles concernent ~85% des plantes, mais leur histoire évolutive reste peu connue. De rares traces fossiles trouvées dans les premiers environnements terrestres offrent cependant des informations capitales. Il est toutefois très difficile de visualiser ces structures symbiotiques à l’échelle microscopique. Dans cet article nous avons utilisé la microscopie confocale laser associée à la microscopie de temps de vie de fluorescence (FLIM) pour étudier un nouveau champignon et les structures cellulaires d’une plante du chert de Windyfield datant de 407 million d’années. Ce niveau géologique est distinct du chert de Rhynie, l’autre niveau fossilifère situé dans le village de Rhynie en Ecosse. Nous avons aussi utilisé la spectroscopie Raman pour examiner la composition carbonée des tissus du champignon et de la plante. Cette approche intégrée a permis de révéler les structures fongiques avec des détails jamais obtenus jusqu’alors. Le champignon Rugosomycetes lavoisieriae gen. nov., sp. nov. possède des caractères similaires à ceux des champignons mycorhiziens actuels du groupe des Glomeromycotina. C’est la première fois que l’on observe des mycorhizes dans le chert de Windyfield. La technique FLIM a permis d’observer des détails au niveau subcellulaire. La spectroscopie Raman, elle, a montré que les arbuscules fongiques et les vésicules du système conducteur de la plante avaient subi des altérations géologiques, et avaient maintenant la même composition chimique. Ces résultats permettent de mieux comprendre ces symbioses anciennes, et extrêmement rares, entre la plante et le champignon. Ils montrent aussi le potentiel de l’approche combinée Confocal‐FLIM pour les recherches en paléobotanique. Las asociaciones micorrízicas entre hongos y plantas son fundamentales para los ecosistemas terrestres. Aunque las micorrizas están presentes en aproximadamente el 85 % de las plantas existentes, sus registros geológicos siguen siendo escasos. La escasa evidencia fósil existente de los primeros ambientes terrestres ofrece información crucial sobre estas antiguas simbiosis. Sin embargo, es todo un reto visualizar fósiles de hongos dentro de los tejidos vegetales a las pequeñas escalas requeridas. En este estudio se combinan la microscopía confocal láser de barrido y la microscopía de imágenes de tiempo de vida de fluorescencia (FLIM) para investigar la asociación micorrízica entre una nueva especie de hongo y las estructuras celulares en una planta de 407 millones de años de antigüedad. Las muestras proceden del Windyfield Chert, una unidad estratigráfica fosilífera definida situada en Rhynie (Escocia). También se utilizó la espectroscopia Raman para investigar la estructura de carbono de los tejidos fúngicos y vegetales. Este enfoque integrado reveló estructuras fúngicas con un nivel de detalle sin precedentes. El hongo, Rugososporomyces lavoisieriae gen. nov., sp. nov., presenta características similares a las de los hongos micorrízicos arbusculares Glomeromycotina ahora existentes. Este es el primer registro de micorrizas en el Windyfield Chert. La FLIM fue capaz de identificar características a nivel subcelular, mientras que la espectroscopia Raman mostró que los arbúsculos fúngicos y las vesículas de las células conductoras de agua de las plantas fueron alteradas geologicamente, lo que resultó en una composicion química similar de ambas. Estos hallazgos únicos amplían nuestra comprensión de simbiosis entre plantas y hongos my antiguas y muy infrecuentes, a la vez que resaltan el potencial de la combinación de las técnicas Confocal‐FLIM para el avance de la investigación paleobotánica.

Marine sediments are a large reservoir of recalcitrant organic matter and host microbes at subsurface depths exceeding 2.4 kilometers and temperatures up to 120°C, yet the mechanisms supplying bioavailable substrates remain unclear. Here, we investigated 7.8-million-year-old sediment from IODP Site C0012 off the Nankai Trough, Japan, through incubations at 20°, 35°, 55°, and 85°C to simulate burial temperatures. Using 3D fluorescence spectroscopy and ultrahigh-resolution mass spectrometry, we tracked changes in dissolved organic matter (DOM). At 35°C, humic-like DOM was released alongside metal ions, exhibiting low bioavailability. At 55°C, abiotic decomposition of humic compounds generated smaller, more bioavailable DOM, promoting fermentation. At 85°C, large nitrogen-containing humic compounds decomposed, producing labile H2 and acetate mainly through abiotic processes, bypassing fermentation. Our findings show how abiotic thermal processes activate the refractory organic matter pool, advancing our understanding of long-term carbon sequestration in marine sediments and its implications for global carbon cycling.

Here, we report fossil isopods preserved in laminated oil-shale mudstone (dysodile) from the Lower Cretaceous of Lebanon (Lower Barremian, 125 Ma, Grès du Liban Alloformation, Jezzine District). Based on a variety of proxies, their palaeoenvironments are determined to have been a shallow freshwater lake. The fossil isopods were studied using modern imaging techniques, such as multispectral imaging and photometric stereo, allowing for a detailed comparison of these specimens with comparable extant and fossil taxa. The conspecific fossils are herein recognized as remains of a new species-†Dysopodus gezei gen. et sp. nov.-of uncertain affinity within Cymothoida and bearing a strong resemblance to its non-parasitic lineages (Cirolanidae). A conspicuous pleotelson and uropod morphology set it apart from most species, with the notable exception of †Pseudoplakolana chiapaneca gen. nov. et comb. nov. from the Cretaceous of Mexico, originally attributed to an Australasian lineage (herein disputed). So far, the biogeographical distribution of the peri-Mediterranean underground fauna has predominantly been explained through a passive isolation process of former marine species, driven by regressing coastlines. Stemming from a freshwater lake environment, the 125 million-year-old fossils from Lebanon provide an unconventional perspective on the evolutionary origin of extant cave- and groundwater-dwelling cymothoidans.

Species are a fundamental unit of biodiversity. Yet, the existence of clear species boundaries among bacteria has long been a subject of debate. Here, we studied species boundaries in the context of the phylogenetic history of Nostoc, a widespread genus of photoautotrophic and nitrogen-fixing cyanobacteria that includes many lineages that form symbiotic associations with plants (e.g. cycads and bryophytes) and fungi (e.g. cyanolichens). We found that the evolution of Nostoc was characterized by eight rapid radiations, many of which were associated with major events in the evolution of plants. In addition, incomplete lineage sorting associated with these rapid radiations outweighed reticulations during Nostoc evolution. We then show that the pattern of diversification of Nostoc shapes the distribution of average nucleotide identities (ANIs) into a complex mosaic, wherein some closely related clades are clearly isolated from each other by gaps in genomic similarity, while others form a continuum where genomic species boundaries are expected. Nevertheless, recently diverged Nostoc lineages often form cohesive clades that are maintained by within-clade gene flow. Boundaries to homologous recombination between these cohesive clades persist even when the potential for gene flow is high, i.e. when closely related clades of Nostoc co-occur or are locally found in symbiotic associations with the same lichen-forming fungal species. Our results demonstrate that rapid radiations are major contributors to the complex speciation history of Nostoc. This underscores the need to consider evolutionary information beyond thresholds of genomic similarity to delimit biologically meaningful units of biodiversity for bacteria.

The Paleozoic fossil record provides unique insights into the evolution of life history traits through the direct preservation of interspecific interactions in deep time. However, evidence of direct interactions between different species is relatively rare even among localities with exceptional soft-tissue preservation. Here we provide evidence of parasitic organisms from the Fezouata Shale biota of Morocco. Seven specimens of the bivalve mollusk Babinka show highly characteristic, question mark-shaped shell borings consistent with those produced by modern and fossil parasitic spionid polychetes. This suggests that the spionid polychetes, or polychetes with behavior consistent with spionids, were present in the Early Ordovician, a significant biostratigraphic shift in their temporal origins from their accepted Devonian occurrence. Many unique life history strategies which were significant components of the Fezouata Shale biota remain undiscovered, despite the high concentration of taxonomic attention on the site.

Allopolyploidy, a phenomenon prevalent in angiosperms involving hybridization and whole-genome duplication, results in species with multiple subgenomes, altering genome structure and gene expression, leading to novel phenotypes. Allopolyploids often experience unbalanced homeolog expression bias, the preferential expression of homeologs from one of the two progenitor genomes. To explore the consequences of allopolyploidy and unbalanced homeolog expression bias, we investigate global gene expression and the fate of homeologs in Nicotiana (Solanaceae). We focus on Nicotiana section Repandae, including three allotetraploid species, Nicotiana nudicaulis, N. repanda, and N. stocktonii, derived from diploid progenitors N. sylvestris and N. obtusifolia ∼4.3 Ma. We identify genes with differential expression and investigate expression of candidate genes for flower size variation. Our results show expression differences with the allopolyploids intermediate between the two progenitor species, with a slight bias toward N. obtusifolia. Moreover, we demonstrate unbalanced homeolog expression bias toward the N. obtusifolia subgenome across developmental stages in the allopolyploids, with a stronger bias in N. nudicaulis. In contrast, unbalanced homeolog expression bias shifts toward N. sylvestris for flower size genes in N. nudicaulis, showing that genes involved in particular phenotypes can display different patterns of unbalanced homeolog expression than the overall transcriptome. We also see differential expression of several known flower size genes across corolla developmental stages. Our results highlight the role of unbalanced homeolog expression bias in shaping the evolutionary trajectory of Nicotiana species and provide a foundation for future research into the ecological and evolutionary implications of allopolyploidy in flowering plants.

Gill-skeleton modifications for processing prey represent a major source of functional innovation in living ray-finned fishes. Here we present the oldest actinopterygian tongue bite, derived from the gill skeleton, in the Middle Pennsylvanian (approx. 310 Ma) †Platysomus parvulus. Unrelated to extant tongue biters, this deep-bodied taxon possesses a large, multipartite basibranchial tooth plate opposing an upper tooth field centred on the vomer. This branchial structure occurs in conjunction with toothed jaws, indicating a role for both the basibranchial plate and jaws in feeding. †P. parvulus illustrates the assembly of the tongue bite in the geologically younger †Bobasatraniidae: large opposing dorsal (vomerine) and ventral (basibranchial) crushing plates associated with toothless jaws. The origin of tongue bites falls within the Carboniferous actinopterygian radiation, although it postdates the first signs of the consumption of hard prey (durophagy) in other ray-finned lineages by several million years. This lends support to a protracted model of actinopterygian diversification in the aftermath of the end-Devonian extinction.

暂无摘要（点击查看详情）

暂无摘要（点击查看详情）

The most distant galaxies detected were seen when the Universe was a scant 5% of its current age. At these times, progenitors of galaxies such as the Milky Way were about 10,000 times less massive. Using the James Webb Space Telescope (JWST) combined with magnification from gravitational lensing, these low-mass galaxies can not only be detected but also be studied in detail. Here we present JWST observations of a strongly lensed galaxy at zspec = 8.296 ± 0.001, showing massive star clusters (the Firefly Sparkle) cocooned in a diffuse arc in the Canadian Unbiased Cluster Survey (CANUCS)1. The Firefly Sparkle exhibits traits of a young, gas-rich galaxy in its early formation stage. The mass of the galaxy is concentrated in 10 star clusters (49-57% of total mass), with individual masses ranging from 105M⊙ to 106M⊙. These unresolved clusters have high surface densities (>103M⊙ pc-2), exceeding those of Milky Way globular clusters and young star clusters in nearby galaxies. The central cluster shows a nebular-dominated spectrum, low metallicity, high gas density and high electron temperature, hinting at a top-heavy initial mass function. These observations provide our first spectrophotometric view of a typical galaxy in its early stages, in a 600-million-year-old Universe.

A hominin mandible, KNM-ER 63000, and associated vertebrate remains were recovered in 2011 from Area 40 in East Turkana, Kenya. Tephrostratigraphic and magnetostratigraphic analyses indicate that these fossils date to ∼4.3 Ma. KNM-ER 63000 consists of articulating but worn and weathered mandibular corpora, with a broken right M2 crown and alveoli preserved at other tooth positions. Despite extensive damage, KNM-ER 63000 preserves diagnostic anatomy permitting attribution to Australopithecus anamensis. It can be distinguished from Australopithecus afarensis by its strongly inclined symphyseal axis with a basally convex, 'cut-away' external surface, a lateral corpus that sweeps inferomedially beneath the canine-premolar row, and alignment of the canine alveolus with the postcanine axis. KNM-ER 63000 is distinguished from Ardipithecus ramidus by its thick mandibular corpus and large M2 crown. The functional trait structure and enamel's stable carbon isotopic composition of the Area 40 large-mammal community suggests an environment comparable to Kanapoi and other ∼4.5-4 Ma eastern African sites that would have offered Au. anamensis access to both C3 and C4 food resources. With an age of ∼4.3 Ma, KNM-ER 63000 is the oldest known specimen of Au. anamensis, predating the Kanapoi and Asa Issie samples by at least ∼100 kyr. This specimen extends the known temporal range of Au. anamensis and places it in temporal overlap with fossils of Ar. ramidus from Gona, Ethiopia. The morphology of KNM-ER 63000 indicates that the reconfigured masticatory system differentiating basal hominins from the earliest australopiths existed in the narrow temporal window, if any, separating the two. The very close temporal juxtaposition of these significant morphological and adaptive differences implies that Ar. ramidus was a relative rather than a direct phyletic ancestor of earliest Australopithecus.

Petaluridae (Odonata: Anisoptera) is a relict dragonfly family, having diverged from its sister family in the Jurassic, of eleven species that are notable among odonates (dragonflies and damselflies) for their exclusive use of fen and bog habitats, their burrowing behavior as nymphs, large body size as adults, and extended lifespans. To date, several nodes within this family remain unresolved, limiting the study of the evolution of this peculiar family. Using an anchored hybrid enrichment dataset of over 900 loci we reconstructed the species tree of Petaluridae. To estimate the temporal origin of the genera within this family, we used a set of well-vetted fossils and a relaxed molecular clock model in a divergence time estimation analysis. We estimate that Petaluridae originated in the early Cretaceous and confirm the existence of monophyletic Gondwanan and Laurasian clades within the family. Our relaxed molecular clock analysis estimated that these clades diverged from their MRCA approximately 160 mya. Extant lineages within this family were identified to have persisted from 6 (Uropetala) to 120 million years (Phenes). Our biogeographical analyses focusing on a set of key regions suggest that divergence within Petaluridae is largely correlated with continental drift, the exposure of land bridges, and the development of mountain ranges. Our results support the hypothesis that species within Petaluridae have persisted for tens of millions of years, with little fossil evidence to suggest widespread extinction in the family, despite optimal conditions for the fossilization of nymphs. Petaluridae appear to be a rare example of habitat specialists that have persisted for tens of millions of years.