DOI: 10.5061/dryad.dh46139
title: Data from: The Rapoport effect and the climatic variability hypothesis in Early Jurassic ammonites

description: The increase of species range size towards high latitudes, known as the
 Rapoport’s rule, remains one of the most debated and poorly understood
 macroecological patterns. Numerous studies have challenged both its
 universality and the main mechanism originally proposed to explain it,
 i.e. the climatic variability hypothesis. Here we study this pattern on a
 group of fossil marine organisms: the early Pliensbachian ammonites of the
 western Tethys. We further take into account the influence of the marked
 provincialism prevailing at that time, with a Mediterranean province (MED)
 and a Northwest European province (NWE) located on each side of a
 latitudinally-oriented palaeobiogeographic barrier. We find that only
 species from the NWE province display a Rapoport effect, whereas species
 from the more tropical MED province show a boundary effect and have larger
 range sizes in average. This dual pattern can be explained by an
 alternative climatic variability hypothesis that better captures
 latitudinal seasonal variations and outlines the influence of the
 intertropical zone, characterized by stable and homogeneous climate that
 allows species to disperse over very large areas, regardless of their
 thermal tolerance. Accordingly, the NWE province probably displayed a
 gradient of seasonal climatic variations which caused the emergence of a
 Rapoport effect, whereas the MED province was probably located in the
 intertropical zone where no gradient in species range size is expected.
 Our multi-scale approach further shows that the Rapoport effect is scale
 dependent and may be labile through time. This probably explains the
 conflicting results of previous studies carried out at various
 spatio-temporal scales.
description: Phylogenetic hypothesis
 for early Pliensbachian ammonitesPhylogenetic hypothesis
 for early Pliensbachian ammonites of the western Tethys provided in
 parenthetical format for the entire dataset and for each subdataset
 analyzed in this studySupplementary figure 1.
 Species-level phylogenetic hypothesis for ammonites of the western Tethys,
 for the entire early Pliensbachian and for each chronozone of this
 substageSpecies-level
 phylogenetic hypothesis for early Pliensbachian ammonites (214 sp; after
 Hardy et al. 2012) together with their province(s) of occurrence (A); and
 subtrees for species of the Jamesoni (B; 132 sp), Ibex (C; 103 sp) and
 Davoei (D; 45 sp) chronozones. Inter-species phylogenetic distances
 correspond to branch lengths between each species pair in the phylogeny.
 Abbreviations: MED, Mediterranean; NWE, Northwest European; sp,
 species.Zacaietal_SuppFig1.pdfSupplementary figure 2. Spatial distribution of western Tethys fossiliferous localities and of fossiliferous localities containing endemic species for each chronozone of the early PliensbachianSpatial distribution of western Tethys fossiliferous localities and of fossiliferous localities containing endemic species for each chronozone of the early PliensbachianZacaietal_SuppFig2.pdfSupplementary table 1. Datasets analyzed to test for the existence of a Rapoport effect in early Pliensbachian ammonites of the western TethysDatasets analyzed to test for the existence of a Rapoport effect in early Pliensbachian ammonites (first Excel sheet), and for the three chronozones of this substage (following Excel sheets)Zacaietal_SuppTable1.xlsxSupplementary table 2. Results of GEE models testing the relationship between species latitudinal midpoint and range size for trans-province species and for NWE species without Beaniceras luridumResults of GEE models testing the relationship between species latitudinal midpoint and range size for trans-province species and for NWE species without Beaniceras luridumZacaietal_SuppTable2.xlsxSupplementary table 3. Results of GEE models testing the relationship between species latitudinal midpoint and range size for species with at least two occurrencesResults of GEE models testing the relationship between species latitudinal midpoint and range size for species with at least two occurrencesZacaietal_SuppTable3.xlsx