Evolution of ecospace occupancy by Mesozoic marine tetrapods



Ecology and morphology are different, and yet in comparative studies of fossil vertebrates the two are often conflated. The macroevolution of Mesozoic marine tetrapods has been explored in terms of morphological disparity, but less commonly using ecological-functional categories. Here we use ecospace modelling to quantify ecological disparity across all Mesozoic marine tetrapods. We document the explosive radiation of marine tetrapod groups in the Triassic and their rapid attainment of high ecological disparity. Late Triassic extinctions led to a marked decline in ecological disparity, and the recovery of ecospace and ecological disparity was sluggish in the Early Jurassic. High levels of ecological disparity were again achieved by the Late Jurassic and maintained during the Cretaceous, when the ecospace became saturated by the Late Cretaceous. Sauropterygians, turtles and ichthyosauromorphs were the largest contributors to ecological disparity. Through the Mesozoic, we find that established groups remained ecologically conservative and did not explore occupied or vacant niches. Several parts of ecospace remained vacant for long spans of time. Newly evolved, radiating taxa almost exclusively explored unoccupied ecospace, suggesting that abiotic releases are needed to empty niches and initiate diversification. In the balance of evolutionary drivers in Mesozoic marine tetrapods, abiotic factors were key to initiating diversification events, but biotic factors dominated the subsequent generation of ecological diversity.,The dataset was collected and complied from existing published descriptions of marine tetrapod taxa, references are available with the data.,Supplementary Data Ecospace_data_Reeves_Moon_Benton_Stubbs.xlsx - Taxa list with ecological character codings, with references. Excluded taxa list, with reasons and references. Supplementary_Reeves_Moon_Benton_Stubbs. pdf - File containing supplementary figures 1-7 Supplementary S5 - labelled ecospace.pdf - Seperate file containing supplementary figure 5 Supplementary S6 - temporal ecospace.tiff - Seperate file containing supplementary figure 6 R code and data: READ_ME.txt - life of file names and contents. TIME_BINS_FINAL.txt - geological ages for stage bin FAD_LAD_2020_Revised.txt - geological age data for all taxa, ages are the midpoints of the first bin and last bin colspoi2020_Revised.csv - information to allocate colours and symbols in plots and to assign group memberships EcoNew2020.nex - ecological character codings in NEXUS format to be loaded in R ecospace.scores.txt - NMDS axis 1 and 2 scores Eco space.scores.MATLAB - - NMDS axis 1 and 2 scores for Matlab PA_file_clade_MATLAB - presence/absence data for groups PA_TIME_FILE_MATLAB.txt - presence/absence data for time bins PLOT_PCO_PD_RESULTS - results from MATLAB MDA analysis, for plotting in R PLOT_NMDS_PD_RESULTS - results from MATLAB MDA analysis, for plotting in R PCOa axis scores.txt - PCOa axis scores, representing ecospace occupation in many dimensions PCOa axis scores MATLAB - PCOa axis scores, representing ecospace occupation in many dimensions packing_expansion_results_PCO.txt - results from packing analysis based on PCO scores packing_expansion_results.txt - results from packing analysis based on NMDS scores WMPD_results.txt - WMPD results eco_nmds.rds - object with NMDS output, so it does not have to be rerun (takes around 1 hour to run) R_Code_final.R - R script used to perform analyses and produce plots (associated function scripts: bootstrapWMPD.R, GreedySearch.R, StackPlot.R, UpperTriangle.R, xAxisPeriods.R, results of nmds saved as eco_nmds.rds ),
Date made available9 Sep 2020

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