Fungal Spike Research Articles

Disruption of terrestrial plant ecosystem in Miocene (sub) tropics: A palynological perspective from Fotan Formation, Southeast China

Fern spikes in pollen sequences represent the initial colonization by pioneer species following massive destruction of vegetation. Here, two fern spikes were recognized in the palynological sequences of MP-1 and HK sections from the Miocene Fotan Formation in Zhangpu County, Fujian Province, Southeast China. Based on the occurrences of fern spikes and the law of vegetation succession, we found that at least two catastrophic events occurred in the study area during the Miocene. The contemporaneous flood basalt volcanism in this region is considered to be the main cause for the devastation of terrestrial plant ecosystem, which was followed by the increased runoff as well as the bloom of Concentricystes (algae) as a result of enhanced nutrient inputs after disturbances. Besides, in comparison with MP-1 section, the fern spike in HK section is characteristic of 1) the higher abundance and diversity in terms of the composition of fern spores, 2) the appearance of fungal spike, 3) the longer time of duration, and 4) the much higher abundance of Concentricystes, suggesting that the catastrophic event occurred during the deposition of HK section is more severe than that recorded by MP-1 section.

Evidence for fungal proliferation following the Cretaceous/Paleogene mass-extinction event, based on chemostratigraphy in the Raton and Powder River basins, western North America

The presence of the amino acid α-aminoisobutyric acid (Aib) within Cretaceous/Paleogene (K/Pg) boundary clay in the Raton and Powder River basins in Colorado and Wyoming, respectively, has been described as compelling evidence that extraterrestrial Aib survived the high-energy Chicxulub impact. Based on contemporary experiments and simulations, however, it is highly unlikely that extraterrestrial Aib survived the impact, which had peak impact pressures and temperatures in excess of 600 GPa and 10,000 K, respectively. In other words, the amino acid signature of the carbonaceous chondritic asteroid that impacted Chicxulub was undoubtedly destroyed upon impact during formation of the vapor plume or so-called “fireball.” The only organisms known to produce Aib are the suite (more than 30 genera) of cosmopolitan saprotrophic filamentous fungi that include Trichoderma Pers., which has recently been hypothesized to have thrived during the K/Pg mass-extinction event. Therefore it is proposed that the Aib horizon in the K/Pg boundary clay in the Raton and Powder River basins correlates with the K/Pg boundary fungal spike, which thus far has only been observed in New Zealand (Southern Hemisphere). This proposition is based upon superimposing the Aib horizon on the well-known iridium and fern-spore spikes, as its stratigraphic position precisely matches that predicted by the fungal spike. If correct, this hypothesis alters the conventional perspective on the tempo and mode of terrestrial ecosystem recovery in western North America, as the heavily sampled K/Pg boundary section in the Raton Basin was instrumental in shaping the traditional narrative of the rapid recolonization of a denuded landscape by ferns via wind-blown spores in the immediate wake of regional deforestation caused by the K/Pg impact event. Perhaps more importantly, it could present an alternative to traditional palynological approaches for locating the fungal spike in other terrestrial K/Pg boundary sections and could provide additional support for the generalization that global mass-extinction events are frequently accompanied by fungal spikes.

Palaeoenvironments, flora, and organic carbon and nitrogen isotope changes across the non-marine Permian-Triassic boundary at Wybung Head, Australia

The Permian-Triassic boundary section at Wybung Head, eastern Australia shows a rapid change from humid coal-bearing lowland braided stream through a thin clay and coal breccia and paleosols to semi-arid silty floodplain deposits. Identifiable plant remains and total organic matter disappear above the coal and clay breccia. Three characteristic palynofacies accumulated in a range from oxic to sub-oxic to anoxic conditions. The dominance of opaque phytoclasts in the entire sequence reflects deposition under oxic conditions, especially in the sequence lying above the Birdie Coal, the result of fluctuating water tables, high energy and desiccating conditions. In the Birdie Coal, however, at certain horizons, a water-saturated environment favored the preservation of organic matter such as pollen, spores, and structured organic matter. This latest Permian paleovegetation was dominated by opportunistic understory spore-bearing plants, with a canopy of pollen-bearing glossopterids, conifers and cordaitales. Total organic carbon drops from >30% in the coal, through <5% in the breccia to <1% in the paleosols and silts. The organic δ13C values are constant at ~ −25.5‰ in the coal and coal breccia, but then decrease to less than −27‰ in the paleosols and silts. These results confirm the rapid sedimentary, floral and organic carbon isotope changes across the non-marine Permian-Triassic boundary in eastern Australia. Our δ13Corg values suggest a significant and sustained negative δ13Corg excursion, with a magnitude of about 3‰, above the Birdie Coal. Unlike δ13Corg, there is no clear trend in δ15Norg values. The low C/N ratios of 10 and less, of the samples above +55 cm, are only found in modern burned soils with low bacteria/fungi ratios or in decaying wood. There is no obvious fungal spike in the Wybung Head section, may have been destroyed during the formation of this soil B horizon, as elsewhere a global fungal spike layer marks an interval of decreased terrestrial biomass and decaying vegetation associated with the Permian-Triassic crisis and boundary. Two negative excursions in the uppermost Permian and lowest Triassic can be correlated throughout Gondwana.

TERRESTRIAL BIOTIC CRISES: PALEOBOTANICAL RECORD AND INTERPRETATION

The controversial problem of biotic crises is considered in relation to the Cretaceous - Tertiary and Permian - Triassic transboundary events in the nonmarine sequence of Far East and the Russian platform, respectively. In both cases, the floristic changes across the critical boundaries proceeded in few steps, none of which indicated a catastrophic destruction of plant communities. Rather the vegetational changes were related to a spread of continental climates, downslope migrations of altitudinal belts and deciduousness. Neither the end-Permian "fungal spike", nor the end-Cretaceous "fern spike" are supported by paleobotanical evidence. Incidentally, an increase of ferns in the transboundary plant-bearing sequences can be explained, upon the recent examples, by the rapid fern growth on the ash fallouts. A model of biotic crises is proposed, in which the intracratonic rifting and trap magmatism are causally related to the rise/spheric expansion of continental crust. A concerted impact of environmental changes was manifested at the beta level diversity in the first place, e.g. the reduction of wetlands and eutrophication of aquatic ecosystems, with a consequential loss of their alpha diversity

Interpretation of “fungal spikes” in Permian-Triassic boundary sections

Abundant occurrences of the palynomorph Reduviasporonites have been described as “fungal spike” from several Permian/Triassic boundary sections and related to the supposed destruction of woody vegetation by fungal pathogens during the Permian/Triassic extinction event. The biological affinity of this taxa considered by some authors of fungal origin is still controversially discussed since there is geochemical evidence that it is most probably related to algae. The abundance peak of this species is used by some authors as a stratigraphic marker, notably in terrestrial Permian/Triassic boundary sections from South China. Illustrations of the reported fungal remains however show potentially erroneous taxonomic identification of Reduviasporonites, and, based on differences in thermal maturation, they may represent recent contamination. Here Reduviasporonites chalastus of Early Triassic age is illustrated together with recent fungal remains originating from a strongly weathered and otherwise barren sample from a Middle Triassic section.

Terrestrial paleoenvironment characterization across the Permian–Triassic boundary in South China

Well-preserved marine fossils in carbonate rocks permit detailed studies of the end-Permian extinction event in the marine realm. However, the rarity of fossils in terrestrial depositional environments makes it more challenging to attain a satisfactory degree of resolution to describe the biotic turnover on land. Here we present new sedimentological, paleontological and geochemical (X-ray fluorescence) analysis from the study of four terrestrial sections (Chahe, Zhejue, Mide and Jiucaichong) in Western Guizhou and Eastern Yunnan (Yangtze Platform, South China) to evaluate paleoenvironmental changes through the Permian–Triassic transition.Our results show major differences in the depositional environments between the Permian Xuanwei and the Triassic Kayitou formations with a change from fluvial–lacustrine to coastal marine settings. This change is associated with a drastic modification of the preservation mode of the fossil plants, from large compressions to small comminuted debris. Plant fossils spanning the Permian–Triassic boundary show the existence of two distinct assemblages: In the Xuanwei Formation, a Late Permian (Changhsingian) assemblage with characteristic Cathaysian wetland plants (mainly Gigantopteris dictyophylloides, Gigantonoclea guizhouensis, G. nicotianaefolia, G. plumosa, G. hallei, Lobatannularia heinanensis, L. cathaysiana, L. multifolia, Annularia pingloensis, A. shirakii, Paracalamites stenocostatus, Cordaites sp.) is identified. In the lowermost Kayitou Formation, an Early Triassic (Induan) Annalepis–Peltaspermum assemblage is shown, associated with very rare, relictual gigantopterids. Palynological samples are poor, and low yield samples show assemblages almost exclusively represented by spores. A ∼1m thick zone enriched in putative fungal spores was identified near the top of the Xuanwei Formation, including diverse multicellular forms, such as Reduviasporonites sp. This interval likely corresponds to the PTB “fungal spike” conventionally associated with land denudation and ecosystem collapse. While the floral turnover is evident, further studies based on plant diversity would be required in order to assess contribution linked to the end-Permian mass extinction versus local paleoenvironmental changes associated with the transition between the Xuanwei and Kayitou formations.

Later Permian acritarchs from Meishan (SE China) in the context of Permian palaeobiogeography and palaeoecology

New palynological observations on the Upper Permian of the stratotype area of the Permian/Triassic boundary Meishan, Zhejiang Province, SE China, reveal the presence of rich, but poorly diversified acritarch assemblages, dominated by the Micrhystridium-Veryhachium complex. The palynological assemblage also includes few pollen and spores, scolecodonts, foraminiferal linings and sporadic specimens of Reduviasporonites, a palynomorph that was commonly considered to be a organism, but that is currently attributed to the algae. Our observations indicate the occurrence of an acritarch assemblage typical for Permian offshore environments, but do not provide evidence for a fungal spike that may reflect saprophytic activity related to dead vegetation formed during the extinction event of the end-Permian.

Fungal proliferation at the Cretaceous-Tertiary boundary.

We have found that a fungal spike occurs between the diverse Late Cretaceous palynoflora and the low-diversity fern-dominated early Paleocene assemblages in a New Zealand section. The fungal layer is coincident with the Ir anomaly marking the extinction event.

Fungal abundance spike and the Permian–Triassic boundary in the Karoo Supergroup (South Africa)

The most severe mass extinction of marine species and terrestrial vertebrates and plants is associated with the Permian–Triassic boundary (∼251 Ma). The extinction interval is also marked by the disappearance of most Late Permian gymnosperm palynomorphs at a layer containing solely the abundant remains of fungi. This ‘fungal spike’ apparently represents widespread devastation of arboreous vegetation. Stratigraphic and palynological study of the Carlton Heights section in the southern Karoo Basin of South Africa revealed a 1-m-thick fungal spike zone that occurs simultaneously with the last appearance of typically Late Permian gymnosperm pollen. The plant extinction and fungal spike zone are found above the last occurrence of Late Permian mammal-like reptiles of the Dicynodont Zone at other Karoo sections. Using the fungal event as a time line in marine and non-marine sections allows placement of the marine extinctions and the extinction of terrestrial plants and reptiles within a brief crisis interval of less than about 40 000 years at the end of the Permian.

Some aspects of the Permian–Triassic boundary (PTB) and of the possible causes for the biotic crisis around this boundary

The first appearance datum (FAD) of Hindeodus parvus is an excellent datum very close to the base of the Otoceras woodwardi Zone (priority base of the Triassic). For the first time, it allows an exact correlation of the PTB in all marine facies and faunal realms. The following features of the extinction and recovery patterns near the PTB are most important for the search for causes of the PTB biotic crisis: (1) most strongly affected were the (siliceous) plankton (radiolarians) and the warm-water benthos and nekton; (2) most of the cold-water faunas were not significantly affected; (3) the recovery of the warm-water benthos and siliceous plankton occurred only after an unusually long time (during the late Olenekian and Middle Triassic); (4) the productivity of the terrestrial plants dropped strongly and the recovery was mainly in the upper Olenekian and in the Middle Triassic; (5) several terrestrial extinction events occurred at different levels within the Upper Permian, considerable before the marine PTB; at or close to the FAD of Lystrosaurus no extinction event in the terrestrial faunas can be observed; (6) terrestrial faunal elements that survived the Dzhulfian–Dorashamian extinctions were able to survive some months of extreme climatic conditions by hibernation-like life stages (vertebrates), or by dry- and freezing-resistant eggs (conchostracans); (7) about 50% of the genera that disappeared at the PTB re-appeared in the Olenekian–Middle Triassic interval (Lazarus taxa), or in this time interval genera appeared that had undoubtedly evolved from genera that had disappeared at the PTB; and (8) the PTB is preceded by mass occurrences of marine (and continental?) fungi, and the fungal spike ends abruptly a little before the PTB. A scenario for the PTB biotic crisis is elaborated that takes into consideration: the real (not interpolated) diversity patterns of different marine and continental fossil groups, the exact correlation of bioevents in different faunal realms and facies, the strong biotic crisis in the Tethyan warm-water faunas in contrast to the much weaker biotic event in cold-water faunas, the severe Dzhulfian–Dorashamian climate in many parts of the world caused by the continent–ocean configuration and by Siberian Trap volcanism, the cooling of the Boreal area by the northward drift of Pangaea that interrupted the exchange of warm-water benthos between the Tethys and western North America during the Guadalupian, the extinction event at the Guadalupian–Lopingian boundary that restricted most of the affected warm-water faunas to the Tethys, the importance of lower Scythian anoxia that reached an unusually shallow level, and above all the effects of the contemporaneous huge volcanic events about 250 m.y. ago on the Siberian Platform and in the eastern Tethys that caused a 3–6-months-lasting volcanic winter with strong cooling in low latitudes, followed by a strong global warming.

Fungal event and palynological record of ecological crisis and recovery across the Permian-Triassic boundary

The end of the Permian Period was marked by the most severe mass extinction in the geologic record. Detailed quantitative study of pollen and spores from shallow-marine deposits spanning the Permian-Triassic (P-Tr) boundary in Israel reveals a sequence of palynological-ecological stages reflecting a major crisis among land plants. The disappearance of the gymnosperm-dominated palynoflora of the Late Permian Lueckisporites virkkiae Zone is recorded at a claystone horizon containing almost exclusively abundant fungal remains and carbonized terrestrial plant debris. This ‘‘fungal spike’’ is followed by a zone dominated by marine acritarchs and a succession showing ecological recovery with abundantlycopodsporesandeventualreappearanceofbisaccategymnospermpolleninthe EarlyTriassic.ThelatestPermianproliferationoffungiisrecognizableworldwideandcan be correlated with other paleontological and geochemical markers of a global ecological disaster.