Dunhill, A. M. | Search bioRxiv

bioRxiv2024

A framework for reconstructing ancient food webs using functional trait data

O_LIFood webs provide quantitative insights into the structure and dynamics of ecological communities. Previous work has shown their utility in understanding community responses to modern and ancient perturbations, including anthropogenic change and mass extinctions. However, few ancient food webs have been reconstructed due to difficulties assessing trophic interactions amongst extinct species derived from an incomplete fossil record. C_LIO_LIWe present and assess the Paleo Food web Inference Model (PFIM). PFIM uses functional trait data--predictive of interactions in modern ecosystems and commonly available for fossil organisms--to reconstruct ancient food webs. We test the model by (i) applying it to four modern ecosystems with empirical constrained food webs to directly compare PFIM-constructed networks to their empirical counterparts, (ii) by carefully comparing discrepancies between PFIM-inferred and empirical webs in one of those systems, and (iii) by comparing networks describing feasible trophic interactions ("feasible webs") with networks to which we superimpose characteristic interaction distributions derived from modern theory ("realized webs"). As a proof of concept, we then apply the method to faunal data from two Cambrian fossil deposits to reconstruct ancient trophic systems. C_LIO_LIPFIM-inferred feasible food webs successfully predict [~]70% of trophic interactions across four modern systems. Furthermore, inferred food webs with enforced interaction distributions (i.e., realized webs) accurately predict [~]90% of interactions. Comparisons with a global database of trophic interactions and other food web models, suggest that under sampling of empirical webs accounts for up to 21% of the remaining differences between PFIM and empirical food webs. C_LIO_LIFood webs can be reasonably approximated by inferring trophic interactions based upon life habit traits. This study provides the foundation to use trait-based inference models across the fossil record to examine ancient food webs and community evolution. C_LI

paleontology↗

bioRxiv2022

Extinction cascades, community collapse, and recovery across a Mesozoic hyperthermal event

Biotic interactions and community structure are seldom examined in mass extinction studies but must be considered if we are to truly understand extinction and recovery dynamics at the ecosystem scale. Here, we model shallow marine food web structure across the Toarcian extinction event in the Cleveland Basin, UK using a trait-based inferential modelling framework. First, we subjected our pre-extinction community to extinction cascade simulations in order to identify the nature of extinction selectivity and dynamics. Second, we tracked the pattern and duration of the recovery of ecosystem structure and function following the extinction event. In agreement with postulated scenarios, we found that primary extinctions targeted towards infaunal and epifaunal benthic guilds reproduced the empirical post-extinction community. These results are consistent with geochemical and lithological evidence of an anoxia/dysoxia kill mechanism for this extinction event. Structural and functional metrics show that the extinction event caused a switch from a diverse, stable community with high levels of functional redundancy to a less diverse, more densely connected, and less stable community of generalists. Ecological recovery appears to have lagged behind the recovery of biodiversity, with most metrics only beginning to return to pre-extinction levels [~]7 million years after the extinction event. This protracted pattern supports the theory of delayed benthic ecosystem recovery following mass extinctions even in the face of seemingly recovering taxonomic diversity.

paleontology↗