Fern spike

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Succession of an ecosystem following disturbance, in the form of a fern spike. Fern spike succession.png
Succession of an ecosystem following disturbance, in the form of a fern spike.

In paleontology, a fern spike is the occurrence of unusually high spore abundance of ferns in the fossil record, usually immediately (in a geological sense) after an extinction event. The spikes are believed to represent a large, temporary increase in the number of ferns relative to other terrestrial plants after the extinction or thinning of the latter. Fern spikes are strongly associated with the Cretaceous–Paleogene extinction event, [1] [2] although they have been found in other points of time and space such as at the Triassic-Jurassic boundary. [3] [4] Outside the fossil record, fern spikes have been observed to occur in response to local extinction events, such as the 1980 Mount St. Helens eruption. [5]

Contents

Causes

Extinction events have historically been caused by massive environmental disturbances, such as meteor strikes. Volcanic eruptions can also wipe out local ecosystems through pyroclastic flows and landslides, leaving the ground bare for new colonization. [6] For a population to recover and thrive after such an event, it must be able to tolerate the conditions of the disturbed environment. Ferns have multiple characteristics which predispose them to grow in those environments.

Spore characteristics

Plants generally reproduce with spores or seeds, meaning those will be what germinates in a disaster's aftermath. But spores have advantages over seeds in the environmental conditions produced by a disaster. They are generally produced in higher numbers than seeds, and are smaller, aiding wind dispersal. [6] While many wind-dispersed pollens of seed plants are smaller and farther dispersed than spores, [7] pollen cannot germinate into a plant and must land in a receptive flower. Some seed plants also require animals to disperse their seeds, which may not be present after a disaster. These characteristics allow ferns to rapidly colonize an area with their spores.

Fern spores require light to germinate. [8] Following major disturbances that clear or reduce plant life, the ground would receive ample sunlight that may promote spore germination. Some species' spores contain chlorophyll, which hastens germination and may aid rapid colonization of clear ground. [9]

Environmental tolerance

After the eruption of El Chichón, the fern Pityrogramma calomelanos was observed to regenerate from rhizomes buried by ash, even though the plants' leaves were destroyed. [6] The rhizomes tolerated exposure to heat and sulfur from the volcanic matter. Their survival suggests resilience of ferns to the harsh environmental conditions imposed by certain kinds of disasters, and rhizome regeneration may have been a factor in fern recovery after other environmental events.

Ecology

Fern spikes follow the pattern of ecological succession. In the past and in modern times, ferns have been observed to act as pioneer species. [5] Eventually, their abundance at a site decreases as other plants such as gymnosperms begin to grow. [2]

Spore availability

Fern spikes cannot occur without ferns already existing in the area, so spikes occur primarily in regions where ferns are already a prominent part of the ecosystem. At the Cretaceous-Paleogene extinction event, a fern spike occurred in the New Zealand area, where ferns made up 25% of plant abundance pre-extinction. After the event, fern abundance increased to 90%. [2]

Detection

Prehistoric fern spikes can be detected by sampling sediment. Sources include sediment that has been accumulating in a lake since the event of interest and sedimentary rocks such as sandstone. [5] Because sediment accumulates over time and thus shows superposition, layers can be assigned to certain times. Spore concentration in a layer can be compared to the concentration at different times, and concentration of other particles such a pollen grains. A fern spike is characterized by a suddenly higher abundance of fern spores following a disaster, generally accompanied by a decrease in other plant species as indicated by their pollen. Eventually fern abundance will decrease, hence the term "spike" describing the pattern.

Modern fern spikes can simply be directly observed, and allow for observation of factors contributing to the spike that may not be detectable otherwise, such as rhizomes persisting in ash. [6]

Significance

Because fern spikes generally coincide with certain disasters such as meteorite strikes and volcanic eruptions, their presence in the fossil record can indicate those events. A fern spike is believed to support a meteorite impact as cause of the Triassic-Jurassic extinction event, similar to the one later causing extinction at the end of the Cretaceous period. [3]

Known events

A fern spike followed a fungal spike after the Permian–Triassic extinction event (252 Ma). It has been observed in Australia. [10]

After the Triassic-Jurassic extinction event (201.3 Ma), ferns drastically increased in abundance while seed plants became scarce. The spike has been detected in eastern North America and Europe. [3] [11]

A very widespread fern spike occurred after the Cretaceous–Paleogene extinction event (66 Ma). [2] The spike has been predominantly observed in North America, with just one observance outside the continent in Japan. [1]

Fern spikes today are often observed after volcanic eruptions. The areas affected by the eruptions of Mount St. Helens (May 18, 1980) and El Chichón (March—April 1982) exhibited such a pattern. [5] [6]

See also

Related Research Articles

The Cretaceous is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation Kreide.

<span class="mw-page-title-main">Extinction event</span> Widespread and rapid decrease in the biodiversity on Earth

An extinction event is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the background extinction rate and the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from disagreement as to what constitutes a "major" extinction event, and the data chosen to measure past diversity.

The Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified.

The Mesozoic Era is the second-to-last era of Earth's geological history, lasting from about 252 to 66 million years ago, comprising the Triassic, Jurassic and Cretaceous Periods. It is characterized by the dominance of archosaurian reptiles, like the dinosaurs; an abundance of gymnosperms and ferns; a hot greenhouse climate; and the tectonic break-up of Pangaea. The Mesozoic is the middle of the three eras since complex life evolved: the Paleozoic, the Mesozoic, and the Cenozoic.

<span class="mw-page-title-main">Phanerozoic</span> Fourth and current eon of the geological timescale

The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 538.8 million years ago to the present, and it began with the Cambrian Period, when animals first developed hard shells preserved in the fossil record. The time before the Phanerozoic, called the Precambrian, is now divided into the Hadean, Archaean and Proterozoic eons.

The Triassic is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic.

<span class="mw-page-title-main">Triassic–Jurassic extinction event</span> Mass extinction ending the Triassic period

The Triassic–Jurassic (Tr-J) extinction event (TJME), often called the end-Triassic extinction, marks the boundary between the Triassic and Jurassic periods, 201.4 million years ago, and is one of the top five major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas, the entire class of conodonts and 23–34% of marine genera disappeared. On land, all archosauromorphs other than crocodylomorphs, pterosaurs, and dinosaurs became extinct; some of the groups which died out were previously abundant, such as aetosaurs, phytosaurs, and rauisuchids. Some remaining non-mammalian therapsids and many of the large temnospondyl amphibians had become extinct prior to the Jurassic as well. However, there is still much uncertainty regarding a connection between the Tr-J boundary and terrestrial vertebrates, due to a lack of terrestrial fossils from the Rhaetian (latest) stage of the Triassic. What was left fairly untouched were plants, crocodylomorphs, dinosaurs, pterosaurs and mammals; this allowed the dinosaurs, pterosaurs, and crocodylomorphs to become the dominant land animals for the next 135 million years.

<span class="mw-page-title-main">Osmundaceae</span> Family of ferns

Osmundaceae is a family of ferns containing four to six extant genera and 18–25 known species. It is the only living family of the order Osmundales in the class Polypodiopsida (ferns) or in some classifications the only order in the class Osmundopsida. This is an ancient and fairly isolated group that is often known as the "flowering ferns" because of the striking aspect of the ripe sporangia in Claytosmunda, Osmunda, Osmundastrum, and Plensium. In these genera the sporangia are borne naked on non-laminar pinnules, while Todea and Leptopteris bear sporangia naked on laminar pinnules. Ferns in this family are larger than most other ferns.

<span class="mw-page-title-main">Marsileaceae</span> Family of ferns

Marsileaceae is a small family of heterosporous aquatic and semi-aquatic ferns, though at first sight they do not physically resemble other ferns. The group is commonly known as the "pepperwort family" or as the "water-clover family" because the leaves of the genus Marsilea superficially resemble the leaves of a four-leaf clover. In all, the family contains 3 genera and 50 to 80 species with most of those belonging to Marsilea.

<span class="mw-page-title-main">Central Atlantic magmatic province</span> Largest continental igneous province on Earth

The Central Atlantic magmatic province (CAMP) is the Earth's largest continental large igneous province, covering an area of roughly 11 million km2. It is composed mainly of basalt that formed before Pangaea broke up in the Mesozoic Era, near the end of the Triassic and the beginning of the Jurassic periods. The subsequent breakup of Pangaea created the Atlantic Ocean, but the massive igneous upwelling provided a legacy of basaltic dikes, sills, and lavas now spread over a vast area around the present central North Atlantic Ocean, including large deposits in northwest Africa, southwest Europe, as well as northeast South America and southeast North America. The name and CAMP acronym were proposed by Andrea Marzoli and adopted at a symposium held at the 1999 Spring Meeting of the American Geophysical Union.

<span class="mw-page-title-main">Hanson Formation</span> Geological formation in Ross Dependency, Antarctica

The Hanson Formation is a geologic formation on Mount Kirkpatrick and north Victoria Land, Antarctica. It is one of the two major dinosaur-bearing rock groups found on Antarctica to date; the other is the Snow Hill Island Formation and related formations from the Late Cretaceous of the Antarctic Peninsula. The formation has yielded some Mesozoic specimens, but most of it is as yet unexcavated. Part of the Victoria Group of the Transantarctic Mountains, it lies below the Prebble Formation and above the Falla Formation. The formation includes material from volcanic activity linked to the Karoo-Ferar eruptions of the Lower Jurassic. The climate of the zone was similar to that of modern southern Chile, humid, with a temperature interval of 17–18 degrees. The Hanson Formation is correlated with the Section Peak Formation of the Eisenhower Range and Deep Freeze Range, as well as volcanic deposits on the Convoy Range and Ricker Hills of southern Victoria Land.

<i>Dicroidium</i> Extinct genus of seed ferns

Dicroidium is an extinct genus of fork-leaved seed plants assigned to the order Umkomasiales (corystosperms) that were widely distributed over Gondwana during the Triassic. Their fossils are known from South Africa, the Arabian Peninsula, Australia, New Zealand, South America, Madagascar, the Indian subcontinent and Antarctica. They were first discovered in Triassic sediments of Tasmania by Morris in 1845. Fossils from the Umm Irna Formation in Jordan and in Pakistan indicate that these plants already existed in Late Permian. Late surviving members of the genus are known from the Early Jurassic (Sinemurian) of East Antarctica. Within paleobotany, Dicroidium is a form genus used to refers to the leaves, associated with ovuluate organs classified as Umkomasia and pollen organs classified as Pteruchus, while Dicroidum is also used collectively to refer to the whole plant.

<i>Lepidopteris</i> Extinct genus of seed ferns

Lepidopteris is a form genus for leaves of Late Permian to Early Jurassic Peltaspermaceae, an extinct family of seed plants, which lived from around 260 to 190 million years ago in what is now Australia, Antarctica, India, South America, South Africa, Russia and China. Nine species are currently recognized. Lepidopteris was a common and widespread seed fern, which survived the Permian-Triassic extinction event but succumbed to the Triassic-Jurassic extinction event. Lepidopteris callipteroides is especially common between the first two episodes of Permian-Triassic extinction event, and L. ottonis forms a comparable acme zone immediate before the Triassic-Jurassic extinction event. Lepidopteris would persist into the Early Jurassic in Patagonia, represented by the species Lepidopteris scassoi.

<span class="mw-page-title-main">Cretaceous–Paleogene extinction event</span> Mass extinction event about 66 million years ago

The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary(K–T)extinction, was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs. Most other tetrapods weighing more than 25 kilograms also became extinct, with the exception of some ectothermic species such as sea turtles and crocodilians. It marked the end of the Cretaceous Period, and with it the Mesozoic era, while heralding the beginning of the Cenozoic era, which continues to this day.

<span class="mw-page-title-main">Corystospermaceae</span> Extinct family of seed ferns

Corystosperms are a group of extinct seed plants belonging to the family Corystospermaceae assigned to the order Corystospermales or Umkomasiales. They were first described based on fossils collected by Hamshaw Thomas from the Burnera Waterfall locality near the Umkomaas River of South Africa. Corystosperms are typified by a group of plants that bore forked Dicroidium leaves, Umkomasia cupulate ovulate structures and Pteruchus pollen organs, that were widespread over Gondwana during the Middle and Late Triassic. Other fossil Mesozoic seed plants with similar reproductive structures have also sometimes been included within the "corystosperm" concept sensu lato, such as the "doyleoids" from the Early Cretaceous of North America and Asia. Their oldest records date to the Late Permian from the Umm Irna Formation of Jordan, as well as Pakistan. Late surviving Dicroidium-bearing corystosperms are known from the Early Jurassic (Sinemurian) of East Antarctica. A potential corystosperm sensu lato, the leaf fossil Komlopteris cenozoicus, is known from the Eocene of Tasmania, at least 13 million years after the Cretaceous–Paleogene extinction event.

The Central Skåne Volcanic Province was a site of volcanic activity in the Scania region of Sweden during the Mesozoic Era of the Earth's geological history. The volcanism began with a first and main phase in late Sinemurian to Toarcian times around 191 to 178 Ma. Then volcanism continued sporadically for another 80 million years. More than one hundred volcanic necks of basaltic composition exist in Scania evidencing this volcanism. In central Scania, volcanism was in the form of a volcanic field of cinder cones that had Strombolian eruption styles. These cones produced tuffite deposits made largely of lapilli with rare volcanic bombs. Pyroclastic materials were subsequently palagonitized or largely altered to clay minerals. While eruptions occurred on land the sea was likely very close to the area. Besides purely pyroclastic sediments, lahar deposits have also been identified around the remnants of the volcanoes.

This article records new taxa of fossil plants that are scheduled to be described during the year 2019, as well as other significant discoveries and events related to paleobotany that are scheduled to occur in the year 2019.

<i>Osmundastrum pulchellum</i> Extinct species of fern

Osmundastrum pulchellum is an extinct species of Osmundastrum, leptosporangiate ferns in the family Osmundaceae from the lower Jurassic (Pliensbachian-Toarcian?) Djupadal Formation of Southern Sweden. It remained unstudied for 40 years. It is one of the most exceptional fossil ferns ever found, preserving intact calcified tissue with DNA and cells. Its exceptional preservation has allowed the study of the DNA relationships with extant Osmundaceae ferns, proving a 180-million-year genomic stasis. It has also preserved its biotic interactions and even ongoing mitosis.

This article records new taxa of fossil plants that are scheduled to be described during the year 2021, as well as other significant discoveries and events related to paleobotany that are scheduled to occur in the year 2021.

The fossil history of flowering plants records the development of flowers and other distinctive structures of the angiosperms, now the dominant group of plants on land. The history is controversial as flowering plants appear in great diversity in the Cretaceous, with scanty and debatable records before that, creating a puzzle for evolutionary biologists that Charles Darwin named an "abominable mystery".

References

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  6. 1 2 3 4 5 Spicer, Robert A.; Burnham, Robyn J.; Grant, Paul; Glicken, Harry (1985). "Pityrogramma calomelanos, the Primary, Post-Eruption Colonizer of Volcán Chichonal, Chiapas, Mexico". American Fern Journal. 75 (1): 1–5. doi:10.2307/1546571. JSTOR   1546571.
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  8. ↑ Gantt, Elisabeth; Arnott, Howard J. (January 1965). "Spore Germination and Development of the Young Gametophyte of the Ostrich Fern (Matteuccia struthiopteris)". American Journal of Botany. 52 (1): 82. doi:10.1002/j.1537-2197.1965.tb06760.x. ISSN   0002-9122. JSTOR   2439978.
  9. ↑ Lloyd, Robert M.; Klekowski, Edward J. (1970). "Spore Germination and Viability in Pteridophyta: Evolutionary Significance of Chlorophyllous Spores". Biotropica. 2 (2): 129–137. doi:10.2307/2989770. JSTOR   2989770.
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  11. ↑ Van de Schootbrugge, B.; Quan, T.M.; Lindstrom, S.L.; Püttmann, W.; Heunisch, C.; Pross, J.; Fiebig, J.; Petschick, R.; Rohling, H.G. (August 2009). "Floral changes across the Triassic/Jurassic boundary linked to flood basalt volcanism". Nature Geoscience. 2 (8): 589–594. CiteSeerX   10.1.1.730.9425 . doi:10.1038/ngeo577. ISSN   1752-0908.
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