Biogeographic patterns of olenid trilobites
Description
The biogeographic histories of two cosmopolitan groups of Olenida: Hypermecaspididae and <i>Parabolinella</i> (Olenidae) are studied herein. Different biogeographical models were compared, and the results were discussed in a paleogeographic and palaeoceanographic context. Dispersal pathways were proposed for both groups, identifying potential environmental factors that affected their distribution. Calibrated phylogenetic hypotheses for each taxon were used to compare different models of geographical evolution with the R package BioGeoBEARS. Time-stratified analyses were carried out, using different distance matrices, for three intervals (Furongian, Early Ordovician, and Middle Ordovician). Numbers and types of biogeographical events were estimated under the best-fitting models by using Biogeographic Stochastic Mapping (BSM). The folders include in this project contain the data used in the analysis, the code, and the outputs of the program. The best-fitting model for both groups incorporated jump dispersal, indicating that this was an important speciation strategy. Vicariance was unimportant for these trilobites. The main strategy used for both groups would have been “island hopping”, taking advantage of the microterranes and volcanic island arc chains surrounding Laurentia, Baltica, Avalonia, and Gondwana. Superficial currents generated more homogeneous conditions, allowing dispersal by creeping in <i>Parabolinella</i>. By contrast, in Hypermecaspididae long-distance founder events would have been achieved only by stepping-stone, which is consistent with paleogeographic models that contemplate the development of ocean stratification. The different timings in the evolutionary histories of Parabolinella and Hypermecaspididae would have had an impact on the type and time of the event count inferred for each group. These differences can be explained by the tectonic and climatic changes during the intervals studied. Despite these differences, in both clades, founder and dispersal events were more abundant from the western margin of Gondwana, which constituted an important dispersal center during the Late Cambrian and Early Ordovician.
Files
Steps to reproduce
To calibrate the tree, download the folder "Calibrate": * Open whit an IDE for R the file "run_calibrate.R" * Change your wd in the first line * Run To reproduce the biogeographical analysis download the folder "BioGeo": To compare biogeographical models: * Open with an IDE for R the file "run_all_models.R" located in the folder "run" * Change your wd in the first line * Run Then, for biogeographic stochastic mappings (BSM): * Open the file "run_BSM.R" in the "run" folder * Change your wd in the first line * Run -- Note that the exact BSM count "from to" will differ in each run (given the method is stochastic), but the overall count will be the same --