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Is there a way to generally characterize how species "regrew" after the various mass extinction events happening periodically from 450 Ma to 65 Ma. Would the surviving species just start back where they had left off and evolve willy-nilly as if the destroyed 50% or 70% of biodiverse species had never existed? Or would the biome in some way have the capacity to regrow something resembling the former order based just on the remaining species. This is probably a whopper of a dumb question, my apologies in advance.
I think the concept of adaptive radiation is what you may be thinking about, since adaptive radiations have been observed following historic mass extinctions.
When organisms are placed in environments with low diversity (either due to mass extinction or the recent creation of the environment) they can undergo adaptive radiation. This generally occurs when there are lots of unoccupied niches in the environment - essentially there are lots of potential ways to make a living that are not being exploited by an existing organism.
In this situation, any organism with a heritable trait that was able to utilize a niche better than other organisms would have a selective advantage and would increase in frequency. Over time this process can result in new species of organisms.
There is nothing really different about adaptive radiation and the normal process of evolution and speciation except that in an environment with lots of unoccupied niches, the probability of having a trait that gives you a selective advantage is greater so speciation occurs at a faster rate.
It is the normal processes of evolution and speciation that give the biome the capacity to increase diversity based on the remaining species.
Recovery from the most profound mass extinction of all time
The end-Permian mass extinction, 251 million years (Myr) ago, was the most devastating ecological event of all time, and it was exacerbated by two earlier events at the beginning and end of the Guadalupian, 270 and 260 Myr ago. Ecosystems were destroyed worldwide, communities were restructured and organisms were left struggling to recover. Disaster taxa, such as Lystrosaurus, insinuated themselves into almost every corner of the sparsely populated landscape in the earliest Triassic, and a quick taxonomic recovery apparently occurred on a global scale. However, close study of ecosystem evolution shows that true ecological recovery was slower. After the end-Guadalupian event, faunas began rebuilding complex trophic structures and refilling guilds, but were hit again by the end-Permian event. Taxonomic diversity at the alpha (community) level did not recover to pre-extinction levels it reached only a low plateau after each pulse and continued low into the Late Triassic. Our data showed that though there was an initial rise in cosmopolitanism after the extinction pulses, large drops subsequently occurred and, counter-intuitively, a surprisingly low level of cosmopolitanism was sustained through the Early and Middle Triassic.
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Recoveries and Biodiversity Dynamics
Paleontological discussions of postextinction recoveries have been heavily influenced by models of evolutionary dynamics, particularly competition-driven models governed by the Lotka–Volterra equations and the equilibrial models from MacArthur and Wilson's theory of island biogeography (ref. 1, reviewed in ref. 2). Coupled logistic models have been applied to the dynamics of clades from the fossil record and the patterns of recoveries after mass extinctions (3–6). The models suggest that recoveries will follow a sigmoidal increase to a new equilibrium as survivors radiate into a now-empty ecospace. The sigmoidal shape of such a pattern will produce an apparent lag before an exponential increase, with paleontologists noting the exponential phase as the onset of recovery. The duration of the lag should be proportional to the magnitude of the diversity drop (3, 4). Empirical studies have recognized that many mass extinctions are followed by a survival interval, of variable duration, during which little or no diversification is evident, followed by rapid diversification during a recovery phase (7).
Such equilibrium models give rise to the most common definition of postextinction recoveries: the interval of exponential growth immediately after the end of the extinction, and ending with a decline in origination rates to normal levels as a new equilibrium is approached (7–9). Other definitions have been used, however. Paleoecologists focus on the reappearance of apparently normally functioning ecosystems and emphasize community diversity, structure, and complexity (10). Geochemists have invoked carbon isotopes as a proxy for ecosystem behavior (11). Additionally, different clades may recover at different rates during the same event, and the same clade may recover at different rates in different regions. This ecological and biogeographic texture of biotic recoveries robs many definitions and models of their generality but underscores the complexity of the phenomenon.
Although most analyses of biotic recoveries have focused on individual events, a recent paper involves a time series analysis of the offset between origination and extinction peaks and suggested an approximately 10 million-year lag between the two, irrespective of the magnitude of extinction (12). This lag was found even when the five great mass extinctions were excluded from the analysis. Defining recovery as the interval between a peak in extinction intensity and the subsequent peak in origination is novel, and a lag of this magnitude is not immediately evident after any of the great mass extinctions. The time series analysis is plagued by a number of potential problems, however, and the results will have to be confirmed by future work. The time scale used was not updated with recent information, and hence the 10 million-year lag should best be interpreted as a delay of one stratigraphic time unit before the onset of diversification (13). A delay in the onset of recovery of about 5 million years (myr) has long been apparent in the Early Triassic, after the end-Permian mass extinction, and Sepkoski (14) noted the same pattern after other mass extinction events. He suggested several possible explanations, including preservational artifacts, an artifact resulting from mixing clades with different intrinsic rates of origination (although he discounted this), or a delay in the reestablishment of ecological communities. Variability in origination rates between clades could also produce a synergistic effect in the data (14).
If the results of (12) are valid, they suggest the recovery involves positive feedback, and the active creation of ecospace (12, 13), similar to that recently proposed on the basis of a recent analysis of the delayed recovery of forests in the Early Triassic after the end-Permian mass extinction (15). This pattern of positive feedback is a likely feature of biotic recoveries, irrespective of the validity of ref. 12.
A sixth, or Holocene, mass extinction is currently underway, primarily caused by the activities of Homo sapiens. Since the beginning of the Holocene period, there are numerous extinctions of individual species that are recorded in human writings. Most of these are coincident with the expansion of the European colonies since the 1500s. Some well-known examples are the dodo from Mauritius, the Stellar’s sea cow in northwest North America, the passenger pigeon in North America.
Estimates of Holocene extinction rates are hampered by the fact that most extinctions are probably happening without our even knowing it. While the extinction of a noticeable species of bird or mammal is likely to be observed by humans, especially if it has been hunted or used in some other way, there are many organisms that are of less interest to humans (not necessarily of less value) and many that are undescribed.
We gauge extinction rates against a background extinction rate of approximately 1 extinction per million species per year (or 1 E/MSY), or 1 extinctions per year for every 1 million species on the planet. Let’s put some numbers to this rate to help give it context. Assume there are about ten million species in existence. We would expect that ten species would go extinct each year. One contemporary extinction rate estimate uses the extinctions in the written record since the year 1500. For birds alone this method yields an estimate of 26 E/MSY. Even this seemingly high value may be an underestimate for three reasons:
- many species would not have been described until much later in the time period, so their loss would have gone unnoticed.
- the number of recently extinct species is increasing because extinct species now are being described from skeletal remains.
- some species are probably already extinct even though conservationists are reluctant to name them as such.
Taking these factors into account raises the estimated extinction rate closer to 100 E/MSY. More alarmingly, the predicted rate by the end of the 21 st century is 1500 E/MSY.
Other major mass extinctions
During the past 540 million years, besides the newly discovered end-Guadalupian mass extinction, Earth has had five other mass extinctions. To fully understand the causes and consequences of all mass extinctions, we would need to integrate the fossil record, ocean chemistry changes, atmosphere changes, and tempo of extinction.
The end-Ordovician extinction occurred about 444 million years ago and lost at least 86 percent of the planet’s species. This major event was likely caused by both glaciation and falling sea levels (which was probably due to the rise of Appalachian Mountain Range). The most affected animals were trilobites, brachiopods, and graptolites. The Late Devonian extinction led to the loss of 75 percent of species and occurred about 372 million years ago. Trilobites, for example, became almost completely extinct during this time. One plausible explanation for this huge demise of life was the rise of giant land plants—it led to an excessive amount of nutrients leaking into the ocean, which then led to algal blooms and the depletion of oxygen in the ocean.
Around 251 million years ago, Earth suffered the Permian-Triassic extinction and lost approximately 96 percent of species—the worst in all the planet’s history. A volcanic eruption and large amounts of methane that were secreted by bacteria led to the rapid warming of the planet and to the acidification of the oceans. After that, between 199 and 214 million years ago, we had the Triassic-Jurassic extinction, considered to be caused by the impact of an asteroid and consequent climate change. The latest major extinction occurred in the Cretaceous period, around 66 million years ago, and was the one responsible for the demise of dinosaurs on Earth. Again, an asteroid impact combined with climate change ended much of life on the planet (76 percent of species).
The K–T mass extinctions, however, do not seem to be fully explained by this hypothesis. The stratigraphic record is most complete for extinctions of marine life—foraminifers, ammonites, coccolithophores, and the like. These apparently died out suddenly and simultaneously, and their extinction accords best with the asteroid theory.…
…that contributed to the greatest mass extinction in Earth’s history. Many geologists and paleontologists contend that the Permian extinction occurred over the course of 15 million years during the latter part of the Permian Period (299 million to 252 million years ago). However, others claim that the extinction interval was…
…there have been five notable mass extinctions. A growing number of ecologists, climatologists, and other scientists argue that Earth is now in the midst of its sixth. The purpose of the audio series Postcards from the 6th Mass Extinction is to document this extinction as it happens—and, more importantly, to…
…of these associations is the mass extinction believed by many scientists to have been triggered by a huge impact some 65 million years ago, near the end of the Cretaceous Period. The most-cited victims of this impact were the dinosaurs, whose demise led to the replacement of reptiles by mammals…
The Ordovician Period was terminated by an interval of mass extinction. This extinction interval ranks second in severity to the one that occurred at the boundary between the Permian and Triassic periods in terms of the percentage…
The first known mass extinction ended the Ediacaran. In the Cambrian Period (541 million to 485.4 million years ago) began the great evolutionary radiation that produced most of the known phyla. Evolution occurred rapidly then, as it ordinarily does when adaptive zones are more or less empty and…
The Permian extinction, at the end of the Paleozoic Era, eliminated such major invertebrate groups as the blastoids (an extinct group of echinoderms related to the modern starfish and sea lilies), fusulinids, and trilobites. Other major groups, which included the ammonoids, brachiopods,
The greatest mass extinction episodes in Earth’s history occurred in the latter part of the Permian Period. Although much debate surrounds the timing of the Permian mass extinction, most scientists agree that the episode profoundly affected life on Earth by eliminating about half…
Early Silurian marine faunas recovered from a mass extinction brought on during late Ordovician times by climatic change and lowered sea levels. This mass extinction claimed 26 percent of all marine invertebrate families and 60 percent of all marine invertebrate genera. Only 17…
250th ANNIVERSARY ESSAY
Another major extinction event struck at the close of the Triassic, one that wiped out as much as 20 percent of marine families and many terrestrial vertebrates, including therapsids. The cause of this mass extinction is not yet known but may be related to climatic and oceanographic…
Three of the five largest mass extinctions in Earth history are associated with the Mesozoic: a mass extinction occurred at the boundary between the Mesozoic and the preceding Paleozoic another occurred within the Mesozoic at the end of the Triassic Period and a third occurred at the boundary between the…
Periodic large-scale mass extinctions have occurred throughout the history of life indeed, it is on this basis that the geologic eras were first established. Of the five major mass extinction events, the one best known is the last, which took place at the…
…one of the five largest mass extinctions on Earth. About half of the marine invertebrate genera went extinct at this time whether land plants or terrestrial vertebrates suffered a similar extinction during this interval is unclear. In addition, at least two other Jurassic intervals show heightened faunal turnover affecting mainly…
…of recovery from the major mass extinction that occurred at the Triassic-Jurassic boundary. This extinction eliminated about half of marine invertebrate genera and left some groups with very few surviving species. Diversity increased rapidly for the first four million years (the Hettangian Age [201.3 million to 199.3 million years ago]…
…it is unclear whether the mass extinction at the end of the Triassic had the same impact on terrestrial ecosystems as it did in the oceans. However, there was a distinct change in vertebrate fauna by the Early Jurassic. In Triassic terrestrial ecosystems, synapsids and therapsids—ancestors of modern mammals and…
At or very close to the end of the Cretaceous Period, many animals that were important elements of the Mesozoic world became extinct. On land the dinosaurs perished, but plant life was less affected. Of the planktonic marine flora and fauna, only about…
Theory That Mass Extinctions Have A 27.5 Million Year Cycle Gets A Galactic Twist
For decades scientists have toyed with the idea mass extinctions are not timed randomly, instead operating on a cycle of around 27 million years. A new paper puts more substance behind the idea, but still lacks detail on how the proposed cause might operate.
As soon as the theory an asteroid caused the extinction of the non-avian dinosaurs took hold, people started to wonder if this was a one-off. After all, the end-Cretaceous event is only the most recent of five (or maybe six) periods of catastrophic species loss, prior to the one humans have initiated. Adding in some episodes with somewhat lower death counts led people to notice 25-30 million year cycle, with some gaps where the timing would have predicted an extinction.
The idea of a distant planet, nicknamed Nemesis or Shiva, became briefly popular and is occasionally revived. The idea is that every 30 million years this object's orbit causes it to disturb the path of many comets in the Oort cloud, sending so many of them plunging into the inner solar system that the odds of one hitting Earth skyrocket.
However, once most geologists concluded the bulk of mass extinctions were caused by enormous volcanic eruptions producing massive basalt provinces, with comet strikes the exception, the idea was largely dropped. Now, however, a cross-disciplinary team have revived it, connecting death from the skies and beneath our feet.
Previous claims of cyclic mass extinctions primarily relied on large-scale disappearances of ocean life, where the fossil record is easier to read than on land. Professor Michael Rampino of New York University searched scientific publications for reports of terrestrial extinctions. In Historical Biology, he identifies ten events over the last 300 million years all of which match a 27.5 million-year cycle. Eight of these line up with previously noted marine extinctions.
“It seems that large-body impacts and the pulses of internal Earth activity that create flood-basalt volcanism may be marching to the same 27-million-year drumbeat as the extinctions, perhaps paced by our orbit in the Galaxy,” Rampino said in a statement.
Of Rampino's ten mass extinctions, three have dates matching the largest impact craters of the last 300 million years, fitting the cometary disturbance theory. On the other hand, eight coincide with basalt province-producing eruptions that would have wrecked havoc on the Earth's atmosphere and temperature. (The ends of the Jurrasic and Cretaceous had both.)
The challenge is to explain what mechanism could make these eruptions so regular, let alone line up with impacts from space.
Rampino and co-authors note the Solar System passes through the mid-plane of the galaxy approximately every 26-30 million years. They speculate this could cause increased encounters with dark matter, disturbing cometary orbits, and perhaps have some effect on the Earth's interior processes. Although we don't really understand how, they propose the latter might stimulate mantle plumes that cause massive volcanism.
Researchers unearth 'new' extinction
Credit: CC0 Public Domain
A team of scientists has concluded that earth experienced a previously underestimated severe mass-extinction event, which occurred about 260 million years ago, raising the total of major mass extinctions in the geologic record to six.
"It is crucial that we know the number of severe mass extinctions and their timing in order to investigate their causes," explains Michael Rampino, a professor in New York University's Department of Biology and a co-author of the analysis, which appears in the journal Historical Biology. "Notably, all six major mass extinctions are correlated with devastating environmental upheavals—specifically, massive flood-basalt eruptions, each covering more than a million square kilometers with thick lava flows."
Scientists had previously determined that there were five major mass-extinction events, wiping out large numbers of species and defining the ends of geological periods: the end of the Ordovician (443 million years ago), the Late Devonian (372 million years ago), the Permian (252 million years ago), the Triassic (201 million years ago), and the Cretaceous (66 million years ago). And, in fact, many researchers have raised concerns about the contemporary, ongoing loss of species diversity—a development that might be labeled a "seventh extinction" because such a modern mass extinction, scientists have predicted, could end up being as severe as these past events.
The Historical Biology work, which also included Nanjing University's Shu-zhong Shen, focused on the Guadalupian, or Middle Permian period, which lasted from 272 to about 260 million years ago.
Here, the researchers observe, the end-Guadalupian extinction event—which affected life on land and in the seas—occurred at the same time as the Emeishan flood-basalt eruption that produced the Emeishan Traps, an extensive rock formation, found today in southern China. The eruption's impact was akin to those causing other known severe mass extinctions, Rampino says.
"Massive eruptions such as this one release large amounts of greenhouse gases, specifically carbon dioxide and methane, that cause severe global warming, with warm, oxygen-poor oceans that are not conducive to marine life," he notes.
"In terms of both losses in the number of species and overall ecological damage, the end-Guadalupian event now ranks as a major mass extinction, similar to the other five," the authors write.
Recovery after “Great Dying” Was Slowed by More Extinctions
Researchers studying marine fossil beds have found that the world’s worst mass extinction was followed by two other extinction events, a conclusion that could explain why it took ecosystems millions of years to recover.
AUSTIN, Texas — Researchers studying marine fossil beds in Italy have found that the world’s worst mass extinction was followed by two other extinction events, a conclusion that could explain why it took ecosystems around the globe millions of years to recover.
The extinction events are linked to climate change caused by massive volcanic activity, according to the study published in the journal PLOS ONE on March 15. Lead author William Foster, a postdoctoral researcher in the Jackson School of Geosciences at The University of Texas at Austin, said that this study is a step toward understanding how lifeforms survived during the extinctions, which could help scientists understand how modern ocean life evolved and how it might respond to climate change in the future.
“The early evolution of modern marine ecosystems happened during the recovery period of these extinction events,” Foster said. “Looking at how they responded back then gives us an idea of how they’ll respond to similar factors in the future.”
Earth has experienced five mass extinctions in its history that killed the majority of species living on the planet at the time. The end-Permian extinction or “Great Dying” that occurred about 252 million years ago was the worst, with an estimated 95 percent of marine life and 70 percent of terrestrial life perishing.
The extinction is linked to climate change caused by prolonged volcanic eruptions in Russia’s Siberian Traps. The eruptions covered an area larger than Alaska with lava and released massive amounts of greenhouse gasses into the atmosphere, which had dire consequences for life across the planet.
“This release of carbon dioxide and sulfur started this whole climate warming scenario that caused the extinction,” Foster said.
The end-Permian extinction also had the longest recovery time of any mass extinction, lasting 5 million to 8 million years.
“We had to investigate hundreds of meters of rock before you could see the recovery millions of years later,” Foster said.
In their research paper, Foster and his colleagues provide the first combined fossil and geochemical evidence for two distinct extinction events following the end-Permian that probably played a role in the slow recovery. The evidence comes from rock samples with spikes of carbon 12 relative to carbon 13, a chemical ratio associated with large disruptions in the carbon cycle that were probably caused by the volcanic eruptions.
A carbon 12 spike occurred in samples from the Dienerian, a period about half a million years after the end-Permian extinction that was previously recognized from fossil evidence as an extinction event. A second carbon 12 spike was found at the boundary of the Smithian/Spathian periods, which occur about 1.5 million years after the end-Permian extinction. At both sites Foster and colleagues also noted a decreased diversity of marine fossils compared with surrounding periods, with the dominant survivors of the extinction events being mollusks, such as snails and clams, only a few centimeters in size at most.
After the second extinction event, the fossil record shows an increased ecological diversity. This is a sign, researchers said, that the environmental stresses that limited recovery from the first extinction event and instigated the second were beginning to lessen.
Studying how sea life responded to climate change in the past can help prepare for the potential effects of ongoing and future climate change, said Foster. He pointed out that the changes in ocean conditions that caused the end-Permian mass extinction – ocean acidification, ocean deoxygenation and increasing temperatures – are issues occurring today, though not at the extreme levels recorded in the late stages of the end-Permian extinction.
Study co-author Richard Twitchett, a research leader at the Natural History Museum London, agreed and added that the research provides a better perspective on how environments on Earth have changed over time.
“Our oceans have a long and complex history, have experienced good times and bad, and have been affected by episodes of extreme temperature and climate change,” Twitchett said. “Understanding how the ancestors of living species responded to these past events allows us to put current changes in a proper historical context.”
Researchers from Plymouth University and the University of Georgia also contributed to this study.
Global mass extinctions follow regular 27-million-year cycle, may be linked to Earth’s journey through Milky Way
Mass extinction events affecting land-dwelling animals from mammals and birds to amphibians and reptiles have occurred numerous times throughout our planet&rsquos history, but the researchers concentrated on 10 distinct episodes of intensified extinctions over the past 300 million years.
Their new analysis, published in the journal Historical Biology, finds that mass extinction events closely align with asteroid impacts and increased volcanic activity in the form of flood-basalt eruptions.
&ldquoIt seems that large-body impacts and the pulses of internal Earth activity that create flood-basalt volcanism may be marching to the same 27-million-year drumbeat as the extinctions, perhaps paced by our orbit in the galaxy,&rdquo said Michael Rampino, a professor in New York University&rsquos Department of Biology and the study&rsquos lead author.
Scientists have long studied the mass extinction event roughly 66 million years ago, during which some 70 percent of all species disappeared from the face of the Earth.
Similar mass extinctions in the world&rsquos oceans also appeared to follow a similar, though slightly shorter, pattern.
Rampino and his colleagues pored over troves of paleontological data and realized there was a strong correlation between the mass extinction events on land and in the seas.
The land-based extinction events appeared to reoccur in 27.5-million-year cycles while the oceanic events followed a 26-million-year cycle.
Impact craters from asteroids and comets striking Earth also appear to follow a pattern that aligns with this 26- to 30-million-year extinction cycle.
Astrophysicists suspect these great die-offs may occur when the solar system passes through the particularly crowded mid-plane of the Milky Way, at which point the Earth is subjected to more cosmic violence than normal.
During these periods, comet showers become more frequent, increasing the likelihood of Earth impact which, in turn, triggers periods of dark and cold caused by vast dust clouds, as well as other threats to life such as wildfires, acid rain, ozone depletion and acidification of the oceans.
&ldquoIn fact, three of the mass annihilations of species on land and in the sea are already known to have occurred at the same times as the three largest impacts of the last 250 million years, each capable of causing a global disaster and resulting mass extinctions,&rdquo Rampino said.
Curiously, eight of the mass die-offs closely studied by the researchers also coincided with flood-basalt eruptions which would also have created planetary conditions that are toxic for many forms of life through an accelerated greenhouse effect which increases acidity in the world&rsquos oceans while reducing oxygen content.
&ldquoThe global mass extinctions were apparently caused by the largest cataclysmic impacts and massive volcanism, perhaps sometimes working in concert,&rdquo Rampino added.