This discovery, based on new research, challenges the widely held assumption that a period of explosive evolution quickly follows for survivors of mass extinctions.
In the absence of competition, the common theory goes, surviving species hurry to adapt, evolving new physical attributes to take advantage of newly opened niches in the ecosystem. But that’s not what researchers found in graptoloid populations that survived a mass extinction about 445 million years ago.
“What we found is more consistent with a different theory, which says you might expect an evolutionary lag as the ecosystem reforms itself and new interspecies relationships form,” said University at Buffalo geology professor Charles E. Mitchell, who led the research.
The research provides insight on how a new mass extinction, possibly one resulting from man-made problems such as deforestation and climate change, might affect life on Earth today.
“How would it affect today’s plankton? How would it affect groups of organisms in general?” asked the paper’s lead author, David W. Bapst, a PhD candidate at the University of Chicago, who studied with Mitchell as an undergraduate.
“The general motivation behind this work is understanding how extinction and evolution of form relate to each other, and the fossil record is the only place where we can do these sort of experiments across long spans of time,” Bapst said.
The research on graptoloids is scheduled to appear the week of Feb. 13 in the online Early Edition of the Proceedings of the National Academy of Sciences.
Other team members included Peter C. Bullock and Michael J. Melchin of St. Francis Xavier University in Nova Scotia, and H. David Sheets of Canisius College in Buffalo, N.Y. The National Science Foundation and Natural Sciences and Engineering Research Council of Canada supported the study.
Graptoloids are an extinct zooplankton that lived in colonies. Because the animals evolved quickly and had a wide geographic range, their fossil record is rich — a trove of information on how species diversify.
Bapst, Mitchell and their colleagues examined two different groups of graptoloids in their study: neograptines and diplograptines. Each kind lived during the Ordovician mass extinction that began about 445 million years ago, but only neograptines survived.
Before the extinction event, diplograptine species were dominant, outnumbering neograptine species. Diplograptines also varied more in their morphology, building colonies of many different shapes.
With diplograptines gone after the Ordovician mass extinction, neograptines had a chance to recover in an environment free of competitors.
According to the popular ecological release hypothesis, a popular theory, these circumstances should have led to a burst of adaptive radiation. In other words, without competition, the neograptines should have diversified rapidly, developing new physical traits — new colonial architectures — to take advantage of ecological niches that the diplograptines once filled.
But that’s not what the researchers found.
To test the adaptive radiation idea, they analyzed the colony forms of 183 neograptine and diplograptine species that lived before, during or after the Ordovician mass extinction — a total of 9 million years of graptoloid history.
This wealth of data enabled the team to track graptoloid evolution with more precision than past studies could. What the researchers discovered looked nothing like adaptive radiation.
Almost immediately following the Ordovician mass extinction, new neograptine species proliferated, as expected. But according to the study, these new species displayed only small changes in form or morphology, not the burst of innovation the release hypothesis predicts. In fact, graptoloids had been evolving new physical traits at a more intensive pace before the extinction event.
Limited morphological innovation among neograptines continued for approximately 2 million years after the extinction, Bapst said.
The lag supports a type of evolution that argues that interactions between co-evolving species help foster diversification. Because such relationships likely take time to develop in a recovering ecosystem, an evolutionary lag of the kind the graptoloid study detected should occur in the wake of a mass extinction.
Another possible explanation is that newly appeared graptoloid species may have differed in ways outside of physical traits, a phenomenon that biologists refer to as non-adaptive radiations. A third possibility is that graptoloids may have experienced evolutionary lag due to their complex mode of growth.
Besides investigating how neograptines fared after the extinction event, the team also analyzed whether colony form alone could explain why neograptines survived the mass extinction while diplograptines disappeared. The scientists concluded that this was unlikely, suggesting a role for other factors such as possible differences in the preferred habitat of the two groups.
Steve Koppes | Newswise Science News
3D technology lets us look into the distant past
20.05.2019 | Eberhard Karls Universität Tübingen
Dangerous pathogens use this sophisticated machinery to infect hosts
20.05.2019 | California Institute of Technology
Engineers at the University of Tokyo continually pioneer new ways to improve battery technology. Professor Atsuo Yamada and his team recently developed a...
With a quantum coprocessor in the cloud, physicists from Innsbruck, Austria, open the door to the simulation of previously unsolvable problems in chemistry, materials research or high-energy physics. The research groups led by Rainer Blatt and Peter Zoller report in the journal Nature how they simulated particle physics phenomena on 20 quantum bits and how the quantum simulator self-verified the result for the first time.
Many scientists are currently working on investigating how quantum advantage can be exploited on hardware already available today. Three years ago, physicists...
'Quantum technologies' utilise the unique phenomena of quantum superposition and entanglement to encode and process information, with potentially profound benefits to a wide range of information technologies from communications to sensing and computing.
However a major challenge in developing these technologies is that the quantum phenomena are very fragile, and only a handful of physical systems have been...
Working group led by physicist Professor Ulrich Nowak at the University of Konstanz, in collaboration with a team of physicists from Johannes Gutenberg University Mainz, demonstrates how skyrmions can be used for the computer concepts of the future
When it comes to performing a calculation destined to arrive at an exact result, humans are hopelessly inferior to the computer. In other areas, humans are...
Scientists develop a molecular recording tool that enables in vivo lineage tracing of embryonic cells
The beginning of new life starts with a fascinating process: A single cell gives rise to progenitor cells that eventually differentiate into the three germ...
29.04.2019 | Event News
17.04.2019 | Event News
15.04.2019 | Event News
20.05.2019 | Materials Sciences
20.05.2019 | Life Sciences
20.05.2019 | Power and Electrical Engineering