DOI: 10.5061/dryad.d51c5b0fs
title: Shifting speciation mode and biogeographic patterns during the Late Ordovician (Sandbian-Katian) in Laurentian brachiopods (Atrypida, Anazygidae)

description: The Late Ordovician was a period of substantial environmental change. The
 co-evolution of Earth systems changes involving tectonic uplift, eustasy,
 and biotic changes are recorded in the Late Ordovician in Laurentia. In
 this study, species of the brachiopod family Anazygidae within the genera
 Zygospira and Catazyga were analyzed to assess dispersal pathways among
 eight sedimentary basins. Stochastic analysis applied to a Bayesian
 phylogeny (Anazygidae_tree.tre) through BioGeoBEARS facilitated estimation
 of speciation events including episodes of vicariance and basin-to-basin
 dispersal events (Anazygidae_geoareas.data) within the clade. Three
 algorithms were implemented and compared (BioGeoBEARS_code.R).
 Dispersal-extinction-cladogenesis (DEC) + jump dispersal parameter was the
 best supported model. For suggestions, advice, or requests related to the
 code and how to re-run our results, please contact the author. 
 Results (b_AICc_table.csv) indicate that Anazygidae originated from an
 ancestral vicariance event, and most subsequent speciation events occurred
 via dispersal (total of 14 distinct episodes). Vicariance events are
 constrained to Mohawkian (Sandbian 2 to Katian 1) time and correlate to
 tectonic events. Dispersal events dominated during Cincinnatian (Katian
 1–4) time and promoted increased diversification of anazygid species.
 Dispersal events are related to epicontinental circulation patterns and
 regional sea level changes and can be linked to connectivity and isolation
 pulses between the mid-continent and southern basins. Dispersal events
 exhibit a directional trend from the mid-continent toward the
 southern-most basins in Laurentia. Long-distance dispersal can be
 explained by jump dispersal events, with marginal-Laurentian islands
 acting as “stepping-stones” for intracratonic species. Anazygid speciation
 declined in the Richmondian (Katian 4). Zygospira and Catazyga became
 extinct in Laurentia as the epicontinental seas drained and climate cooled
 during the late Katian.
description: # Shifting speciation mode and biogeographic patterns during the Late
 Ordovician (Sandbian-Katian) in Laurentian brachiopods (Atrypida,
 Anazygidae) Dataset DOI:
 [10.5061/dryad.d51c5b0fs](10.5061/dryad.d51c5b0fs) ## Description of the
 data and file structure ### Files and variables #### File:
 BioGeoBEARS\_code.R **Description:** R code used in R 4.3.0 with original
 (Matzke, 2013) and adapted comments #### File: Anazygidae\_geoareas.data
 **Description:** Anazygidae_geoareas.data is the file used in the R
 script. It's a .txt file saved as .data. The first line contains the
 number of analyzed taxa (20), the number of total geographic areas (8),
 and the initial letters for each studied geographic area. Presence/absence
 of the taxa in a given geographic area is given by 0 (absence) or 1
 (presence). O = Scoto-Avalonia; W= Western Mid-Continent; U= Upper
 Mississippi Valley; E= Eastern Canada; F= Proximal Foreland basin; N=
 Northern Appalachian Basin; S= Southern Appalachian Basin; and A= Alaska.
 More details on the geographic distribution, and which states/provinces
 these areas refer to are mentioned in the manuscript. #### File:
 Anazygidae\_tree.tre **Description:** It's the analyzed .tre file
 from Vilela-Andrade et al. (2025) #### File: b\_AICc\_table.csv
 **Description:** The .csv file is the exported results from the R code.
 The column "Model" refers to all tested models + J parameters;
 "LnL" refers to the logarithmic likelihood; "d" refers
 to the dispersal rates along each branch; "e" refers to the
 extinction rates along each branch; "j" stands for jump
 dispersal (see original text); AICc refers to the corrected Akaike
 Information Criterion (see Matzke, 2013); and AICc_wt refers to the
 weighted Akaike Information Criterion.