No global collapse of food webs across the Permian–Triassic Mass Extinction
Posted on: 3 May 2026
Preprint posted on 25 February 2026
Ancient webs of life; The authors of the study evaluate the effect of the Permian-Triassic mass extinction (PTME) on marine food-webs and post-extinction recovery.
Selected by Theodora Stougiannou
Categories: ecology, evolutionary biology, paleontology
Ancient webs of life; The authors of the study evaluate the effect of the Permian-Triassic mass extinction (PTME) on marine food-webs and post-extinction recovery.
Life on Earth: Mass extinctions
A mass extinction event can be generally defined as an event during which a large percentage of higher taxa in many different biological groups disappears; this disappearance generally occurs within a relatively small timeframe, on a global scale. However, no universally accepted quantitative definition for mass extinctions yet exists. Often referred to as ‘pulses of extinction’, these often occur near or at the ends of formally recognized geological periods.
Regarding marine extinctions, the ‘pulses of extinction model is the one commonly accepted. Some, however, posit that there is indeed evidence for a large percentage of extinctions occurring as pulses towards the end of geological periods, following a period of significant amount of background extinction [1] (Stanley et al., 2016).
Mass extinctions result in loss of species and can be followed by rapid speciation/increased diversity called adaptive radiation; this results in changes in the fossil record, with mass extinctions often defining boundaries between geological periods in the story of life on Earth.
The Permian-Triassic mass extinction (PTME)
PTME, or as alternatively known, P/T, is a mass extinction event that occurred at the end of the Permian period. While some theorize the event occurred as a series of extinction pulses across a timeframe of 15 million years during the late Permian period, others maintain that the event occurred across a much smaller timeframe, of about 200,000 years.
Based on fossil data found in South China, it is believed that the effects of PTME on marine food webs included truncation of the upper trophic levels, followed by recovery proceeding gradually from primary producers upwards. Despite this generalization, however, groups of aquatic animal groups capable of swimming independent of water currents (nektonic) present in upper levels of the food chains (fishes, ammonoids) are less affected compared to animals groups with limited or no-mobility (non-motile) usually inhabiting the sea floor (benthic groups such as foraminifers, brachiopods) [2] (Karapunar et al., 2026) [3] (Jurikova et al., 2020).
Some questions thus remain:
- Was the disruption to these trophic systems (food chains) global, or did it vary based on location?
- Did the marine food webs collapse from the top levels (top-down collapse)? Did recovery after the PTME (P/T) occur from the bottom-up?
- Did the marine food webs reorganize in the same manner across different locations, or was the reorganization after the extinction also varied depending on geographical location? a uniform, or spatially variable manner?
What are the preprint authors looking at?
The study by Karapunar and team seeks to characterize the loss occurring in marine food webs and the subsequently recovery, following the PTME (or P/T) extinction event. To this end they recreated food webs based on fossil trait data and simulated 17 extinction scenarios; based on these, both direct species losses, as well as secondary losses due to cascading effects could be estimated.
Key aspects of the study
- Though there is extensive species loss across all the sites studied, overall, the trophic structures do not globally collapse; as such, most areas retained 4 trophic levels throughout the extinction event. Trophic levels denote hierarchical steps, that all together constitute a food chain; primary producers, i.e., organisms that generate their own nutrition using either sunlight (photosynthesis), or chemical energy (chemosynthesis) usually constitute the first trophic level. The second level will usually be taken up by primary consumers, organisms that feed exclusively on these primary producers.
- Even as species diversity was lost, higher trophic levels were maintained in almost all the sites evaluated.
- Upper trophic levels were still present in food web communities originating in mid- and high latitudes; loss of marine predators was not global.
- Based on extinction scenario simulations, it could be seen that species loss occurred along variable ecological and physiological axes, depending on location. This shows that different physiological traits were advantageous for survival in different environment during the extinction event, and advantageous versus disadvantageous traits are uniform globally. Previous studies suggested that a single global axis exists, along which species were lost, comprising traits such as low physiological buffering capacity, limiter motility, low respiratory capacity, large size.
- For example, in high-latitude locations (Greenland, Tibet), limited motility was the axis along which species were lost, with preferential loss of non-motile organisms mostly living on the sea floor (benthic).
- In samples from Meishan and the Kashmir, it was observed that loss occurred along the physiological trait of respiratory capacity, with species characterized by low respiratory capacity (foraminifera, echinoderms, bryozoans) affected the most. Extinctions occurring in the Kashmir, however, also include a strong random component as well.
- Species loss along this physiological trait axis (respiratory capacity) also occurred in the tropical Dolomites; in this case, however, taxa with high respiratory capacity were lost instead, such as vertebrates, cephalopods [2] (Karapunar et al., 2026).
- Despite regional variability, some trends in primary extinction selectivity could be observed; namely, it affected primarily taxa with limited motility and physiological constraints, especially non-motile benthic organisms that function as primary consumers and are further characterized by low respiratory capacity (Foraminifera, Brachiopoda, Bryozoa, Cnidaria).
- Species occupying the higher trophic levels, such as nektonic predators found in middle to higher latitude communities (fishes, conodonts) were relatively less affected; this could also explain the rapid diversification occurring in these species post-extinction.
- No single trait confers risk for extinction, as this is mediated by a combination of factors relating to physiology, ecology, life-history and local environmental factors [2] (Karapunar et al., 2026).
- Restructuring of the trophic webs after the extinction event, similar to species loss, was also spatially varied.
- For example, samples from areas in low latitudes (Meishan, Türkiye, Dolomites), exhibit mainly retention of bottom trophic levels, despite losses occurring in benthic primary consumers. These tropic food webs were also more vulnerable to secondary extinction cascades.
- Samples from areas found in mid- to higher latitudes (Tiber, Kashmir, Greenland), show that communities in these locations became increasingly top-heavy, as higher trophic levels of the food webs dominated in these areas.
- This could be explained by both newly evolved species as well as species migrating from other locations. In fact, in these higher latitude systems, entry of predatory fishes, temnospondyls, and cephalopods produced quaternary and quinary trophic levels, increasing both mean and maximum trophic levels in the process.
Why this work is interesting
The work by Karapunar and team offers a glimpse into one of the most severe mass extinction events on this planet; it also shows how the trophic networks reorganize and recover. Additionally, it reflects on how spatially varied restructuring in the trophic web can possibly be affected by distinct elements in the local environments, while at the same time, it helps scientists anticipate how marine ecosystems might behave in cases of modern environmental changes.
For me, this preprint offers a glimpse into different locations across the planet at a time when a severe mass extinction was taking place, severe enough to change the geological record and lead to a new era, the Triassic. How were the marine ecosystems of the time responding to this devastation, across the world? An infographic summary of the main information of the article, along with interesting background information follows.
Glossary
Questions to the authors
- In your study, you utilize samples across 7 regions to evaluate the nature of the effects triggered by the PTME, as well as the response and restructuring of the communities following the event. How many samples do you think is ‘enough’ to have an accurate idea about the state of marine food webs at that particular time during the life history of Earth?
- The fact that primary extinction pressures are varied depending on geographical location is associated with extinction selectivity across a wide variety of physiological traits. Do you think that this variety in primary extinction pressures across different locations reflects the different changing factors in the local environment that was shaping the planet at the time, and in turn, led to this mass extinction event?
References
[1] Stanley SM. Estimates of the magnitudes of major marine mass extinctions in earth history. Proceedings of the National Academy of Sciences 2016;113:E6325–34. https://doi.org/10.1073/pnas.1613094113.
[2 Karapunar B, Strydom T, Beckerman AP, Ridgwell A, Wignall PB, Dunne JA, et al. No global collapse of food webs across the Permian–Triassic Mass Extinction 2026:2026.02.24.707709. https://doi.org/10.64898/2026.02.24.707709.
[3] Jurikova H, Gutjahr M, Wallmann K, Flögel S, Liebetrau V, Posenato R, et al. Permian–Triassic mass extinction pulses driven by major marine carbon cycle perturbations. Nat Geosci 2020;13:745–50. https://doi.org/10.1038/s41561-020-00646-4.
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