EPISODES OF FAUNAL TURNOVER AND INCREASES OF ECOLOGICAL COMPLEXITY ACROSS PALAEOZOIC-MESOZOIC TRANSITION IN MARINE ECOSYSTEMS

The fossil record has showed that marine ecosystems during the Paleozoic-Mesozoic transition exhibited complex transformations both in time and space. How these changes affected the functional structure of marine ecosystems and how historical events and biogeographic components controlled the global functional diversity that led to the marine Mesozoic revolution is unknown. Here, we estimate the ecological-functional diversification using multi-dimensional parameter space to assess the temporal pattern of the functional diversity and how latitudinal gradients and extinction events constraint the functional structure of marine palaeoecosystems. A total of 168,604 occurrences of 5433 genera spanning from middle Permian to Early Jurassic, and from tropical and temperate zone were downloaded from the Paleobiology Database. The lifestyle of each genus was classified following Bambach’s ecospace model. Rarefaction was used to standardize the number of genera analysed per time bin. Patterns of functional diversity were assessed estimating functional richness (FRic), specialization (FS), redundancy (FRe) and functional dispersion (FD) indexes. Each functional parameter was contrasted with a null model to test the structure of the data. Curves of species saturation were generated correlating the FRic and taxic richness for temperate and tropical zones, and Jaccard index was used to track the spatial exchange between temperate and tropical fauna. We found that the Paleozoic-Mesozoic transition showed an increase in the ecological complexity and functional specialization through multi-pulses of change associated to shift in trophic skewing and increases of functional redundancy of ecological traits associates to the escalation hypothesis. Latitudinal migration of species re-establishes the ecosystem functioning after P/Tr and Tr/J extinctions events and the tropical zones hold elevated ecological saturation, which vest rapid recovery after P/Tr extinction, relative to temperate zone. Ecological transformation of marine ecosystems during the Triassic was a process both temporally and spatially complex that links diversity-dependent elements and environmental factors to shape global functional diversity.