Biology subjects

Strydom, T.

Publications and source records attributed to Strydom, T..

3 recordsLinked to original sources

bioRxiv2026

Temporal resolution reshapes dynamics of inferred community structure and extinction selectivity across the Permian-Triassic mass extinction

The Permian-Triassic mass extinction fundamentally restructured ecosystems, yet it remains unresolved whether ecological collapse unfolded gradually or in discrete steps, and how extinction selectivity varied with environmental change. Here, we analyse marine food webs from Meishan (China) at high temporal resolution. We show that trophic structure destabilised prior to peak biodiversity loss, followed by a structural tipping point during the extinction interval when the community became less robust to secondary extinctions. Extinction selectivity shifted substantially across the study interval. During the extinction interval, extinction was concentrated at lower trophic levels, propagating upwards from benthic herbivores to higher-level consumers. Although coarse resolution preserves temporal trends in trophic structure and extinction selectivity, it obscures abrupt transitions, sequential extinction dynamics, and critical shifts in ecological organisation. We demonstrate that temporal resolution governs inference of extinction dynamics, with important implications for reconstructing past ecological crises and interpreting ecosystem responses to rapid environmental change.

paleontology↗

bioRxiv2026

No global collapse of food webs across the Permian-Triassic Mass Extinction

The Permian-Triassic mass extinction (PTME), the Earths most severe biotic crisis associated with extreme environmental perturbations, eliminated >80% of marine species1. However, whether it triggered a globally pervasive top-down collapse of marine food webs, and whether recovery proceeded through bottom-up reassembly, remain unresolved2-4. Here we reconstruct spatially explicit metacommunity food webs from seven regions spanning equatorial to high latitudes to test how extinction dynamics and ecosystem reorganization varied geographically. By integrating estimates of community structure and species interactions, we provide direct inference on trophic disruption across the PTME. Despite catastrophic species loss and flattening of the latitudinal diversity gradient5, trophic collapse was not globally uniform, and higher trophic levels were not globally truncated. Instead, extinction selectivity was spatially heterogenous and tracked environmental severity. Benthic, low-motility herbivores with limited respiratory capacity were disproportionately lost, consistent with intensified warming, deoxygenation and disruption of primary productivity under elevated pCO2. Mid-to high-latitude communities became top-heavy and structurally complex, whereas tropical systems remained bottom-heavy and less robust to secondary extinction. These results demonstrate that trophic disruption and recovery were geographically structured, mediated by environmental forcing, species traits and pre-extinction food-web architecture, with implications for predicting marine ecosystem responses to ongoing climate change.

paleontology↗

bioRxiv2022

Long-term spatially-replicated data show no physical cost to a benefactor species in a facilitative plant-plant interaction

Facilitation is an interaction where one species (the benefactor) positively impacts another (the beneficiary). However, the reciprocal effects of beneficiaries on their benefactors are typically only documented using short-term datasets. We use Azorella selago, a cushion plant species and benefactor, and a co-occurring grass species, Agrostis magellanica, on sub-Antarctic Marion Island, comparing cushion plants and the grasses growing on them over a 13-year period using a correlative approach. We additionally compare the feedback effect of A. magellanica on A. selago identified using our long-term dataset with data collected from a single time period. We hypothesized that A. selago size and vitality would be negatively affected by A. magellanica cover and that the effect of A. magellanica on A. selago would become more negative with increasing beneficiary cover and abiotic-severity, due to, e.g., more intense competition for resources. We additionally hypothesized that A. magellanica cover would increase more on cushion plants with greater dead stem cover, since dead stems do not inhibit grass colonization or growth. The relationship between A. magellanica cover and A. selago size and vitality was not significant in the long-term dataset, and the feedback effect of A. magellanica on A. selago did not vary significantly with altitude or aspect; however, data from a single time period did not consistently identify this same lack of correlation. Moreover, A. selago dead stem cover was not significantly related to an increase in A. magellanica cover over the long term; however, we observed contrasting results from short-term datasets. Long-term datasets may, therefore, be more robust (and practical) for assessing beneficiary feedback effects than conventional approaches, particularly when benefactors are slow-growing. For the first time using a long-term dataset, we show a lack of physical cost to a benefactor species in a facilitative interaction, in contrast to the majority of short-term studies.

ecology↗