Periodic Reporting for period 2 - ECODIV (Ecological diversity of land vertebrates through the largest extinction in Earth history)
Periodo di rendicontazione: 2024-03-01 al 2025-02-28
Contemporary Earth’s ecosystems are threatened by accelerating extinction rates, but their responses to biodiversity losses are not detectable on short-time scales. However, large-scale biodiversity crises, or ‘mass extinctions’, occurred in the past and their long-term effects are detectable and measurable in the fossil record, although still poorly understood. For example, the origin of modern-style ecosystems can be linked to the most severe biodiversity crisis in Earth history at the Permian-Triassic boundary (PTME; ~252 million years ago). This event caused the disappearance of over 70% of vertebrate species: land communities of the Triassic were transformed and recolonised by surviving and entirely new groups of animals that diversified to exploit ecological roles that did not exist in Permian ecosystems. This hints that extinctions may play a fundamental role in driving evolution altering the evolutionary trajectory of ecosystems by altering the composition of ecosystems and by favouring an increase in ecological complexity. Nevertheless, the ecological impacts of mass extinctions and biodiversity crisis on ecosystems are still poorly understood.
ECODIV, explored these gaps of knowledge and developed methods that I used to describe patterns of ecological diversity approaching, during and in the aftermath of the PTME. We first targeted gaps in the fossil-record using on fieldwork and repository data of exceptionally well-preserved and well-sampled ecosystems. Using these data, ECODIV established new ways to quantify and compare patterns of ecological diversity in deep-time that can be used to assess the appearance/disappearance of major groups and their ecological roles in ecosystems across different phases of the PTME.
ECODIV, explored these gaps of knowledge and developed methods that I used to describe patterns of ecological diversity approaching, during and in the aftermath of the PTME. We first targeted gaps in the fossil-record using on fieldwork and repository data of exceptionally well-preserved and well-sampled ecosystems. Using these data, ECODIV established new ways to quantify and compare patterns of ecological diversity in deep-time that can be used to assess the appearance/disappearance of major groups and their ecological roles in ecosystems across different phases of the PTME.
During the outgoing I collected the data and developed the methods to study the ecological structure of deep-time ecosystems (WP1). I compiled lists of species occurrences of well-preserved Permian and Triassic assemblages worldwide using fieldwork data, literature, online repositories, and museum collections. These datasets include data that are regularly ignored (i.e. incomplete specimens, microfossils, footprint) in broad diversity studies (Task 1.1). I participated in fieldwork campaigns with the Palaeobiology Group of Virginia Tech, targeting the Triassic geological formations of the southwest USA (Arizona, Texas, New Mexico). This was important to fill in a major low-latitude gap in the fossil record and collecting new data from the Middle Triassic Moenkopi Formation of Arizona. Fieldwork resulted in the creation of the first collection of Moenkopi Formation vertebrates that will be accessioned to the Utah Museum of Natural History (Task 1.2). Using these novel data, I revised the fossil record of the Middle and Late Triassic formations of the southwest USA and created a new microvertebrate collection (description in progress), a redescription of Anisodontosaurus (one of the first herbivorous reptiles following the PTME), and the creation of extensive datasets of species for following analyses.
I implemented a method that transforms occurrence data into ecological data – a necessary step to quantify metrics of ecological diversity in assemblages (WP2). Each of more than 400 species (summarising over 15000 occurrences) in over 25 assemblages was scored for five ecological traits (body size, diet, habitat, locomotion, growth). I used these data to quantify metrics of ecological significance for each assemblage (e.g. diversity, richness, disparity, and redundancy). The Triassic assemblages of the USA and South Africa were prioritised because of the availability of relevant collections and fossil species during the outgoing phase, however, future work will include additional ~40 other Permian-Triassic assemblages worldwide, for which I began collecting data.
These data were analysed using a new protocol that estimates the ecological properties of extinct assemblages and, for the first time, applies resampling strategies to account for the uneven sampling of different assemblages.
These analyses helped assess the ecological impact of the PTME (WP3). It is known that Permian ecosystems were dominated by synapsids that became only a marginal component of Triassic ecosystems, which were instead dominated by reptiles. Our work on the South Africa Karoo Basin shows that the turnover and evolution of new dominant groups also introduced new ecological roles. These were linked to new anatomical adaptations (diet, locomotion), habitat preferences and physiology (growth strategy). In other words, surviving groups occupied new distinct ecological roles rather than the recycling previously available niches. This indicates that the extinction event had a drastic impact not only on the species composition of terrestrial ecosystems but also on their ecological structure and composition and that the appearance of new ecological roles is linked to the appearance/diversification of new groups.
The patterns of recovery from the PTME were investigated at the local/regional level using the exceptional data (WP4). Thanks to the dataset assembled in WP1, I could explore the ecological recovery of ecosystems in the low-latitude Triassic succession of the southwest of the USA (Arizona, Texas, New Mexico) at unprecedented geographical and stratigraphic scales. Results show that Middle Triassic ecosystems were low-diversity and relatively unstable compared to younger assemblages. I identified a first ‘unstable’ phase of recovery, which extends until the early Late Triassic (Carnian) and is characterised by high turnover and low continuity of groups and ecological roles. Only Norian communities become more stable thanks to the diversification of crocodile-line and bird-line reptiles into new ecological modes.
The project fully achieved training and knowledge transfer objectives and milestones, including the development of research skills (data collection, fieldwork, ecological modelling, resampling, R coding), leadership skills (supervision, teaching), management, science communication, and skill exchange.
Progress and results were disseminated via: one in a peer-review publication (several in preparation), four conference attendances (two conference oral presentations, one poster and one in-person invited presentation; three outreach events; two outreach online talks, via social media and a dedicated webpage on the researcher's website.
I implemented a method that transforms occurrence data into ecological data – a necessary step to quantify metrics of ecological diversity in assemblages (WP2). Each of more than 400 species (summarising over 15000 occurrences) in over 25 assemblages was scored for five ecological traits (body size, diet, habitat, locomotion, growth). I used these data to quantify metrics of ecological significance for each assemblage (e.g. diversity, richness, disparity, and redundancy). The Triassic assemblages of the USA and South Africa were prioritised because of the availability of relevant collections and fossil species during the outgoing phase, however, future work will include additional ~40 other Permian-Triassic assemblages worldwide, for which I began collecting data.
These data were analysed using a new protocol that estimates the ecological properties of extinct assemblages and, for the first time, applies resampling strategies to account for the uneven sampling of different assemblages.
These analyses helped assess the ecological impact of the PTME (WP3). It is known that Permian ecosystems were dominated by synapsids that became only a marginal component of Triassic ecosystems, which were instead dominated by reptiles. Our work on the South Africa Karoo Basin shows that the turnover and evolution of new dominant groups also introduced new ecological roles. These were linked to new anatomical adaptations (diet, locomotion), habitat preferences and physiology (growth strategy). In other words, surviving groups occupied new distinct ecological roles rather than the recycling previously available niches. This indicates that the extinction event had a drastic impact not only on the species composition of terrestrial ecosystems but also on their ecological structure and composition and that the appearance of new ecological roles is linked to the appearance/diversification of new groups.
The patterns of recovery from the PTME were investigated at the local/regional level using the exceptional data (WP4). Thanks to the dataset assembled in WP1, I could explore the ecological recovery of ecosystems in the low-latitude Triassic succession of the southwest of the USA (Arizona, Texas, New Mexico) at unprecedented geographical and stratigraphic scales. Results show that Middle Triassic ecosystems were low-diversity and relatively unstable compared to younger assemblages. I identified a first ‘unstable’ phase of recovery, which extends until the early Late Triassic (Carnian) and is characterised by high turnover and low continuity of groups and ecological roles. Only Norian communities become more stable thanks to the diversification of crocodile-line and bird-line reptiles into new ecological modes.
The project fully achieved training and knowledge transfer objectives and milestones, including the development of research skills (data collection, fieldwork, ecological modelling, resampling, R coding), leadership skills (supervision, teaching), management, science communication, and skill exchange.
Progress and results were disseminated via: one in a peer-review publication (several in preparation), four conference attendances (two conference oral presentations, one poster and one in-person invited presentation; three outreach events; two outreach online talks, via social media and a dedicated webpage on the researcher's website.
ECODIV has produced primary data (new fossil collections) and new tools to study biodiversity in deep-time. The sampling strategy of the project includes data that are largely ignored (e.g. footprints, incomplete and/or indeterminate specimens). A wider range of data translates to a richer and more accurate representation of the past ecosystems than previous methods normally included. ECODIV focus on well-sampled assemblages is key to understand evolutionary and ecological phenomena at the scale they take place, accounts for biases, and improves the resolution of the results.
This project tracked for the first time the evolution of groups and ecological roles, patterns of diversity leading and during the PTME and during the recovery to a degree that has never been achieved before.
Ultimately, ECODIV adopts a strategy that allows to understand better the responses of terrestrial ecosystems through time. Thus, methods and results of this work may be adapted to inform future conservation efforts.
This project tracked for the first time the evolution of groups and ecological roles, patterns of diversity leading and during the PTME and during the recovery to a degree that has never been achieved before.
Ultimately, ECODIV adopts a strategy that allows to understand better the responses of terrestrial ecosystems through time. Thus, methods and results of this work may be adapted to inform future conservation efforts.