DOI: 10.5061/dryad.6n15h
title: Data from: Nonlinear thermal gradients shape broad-scale patterns in geographic range size and can reverse Rapoport’s rule

description: Aim: Species living at latitudes that have greater annual temperature
 variations are expected to achieve broader geographic ranges than species
 living at latitudes that have smaller annual temperature variations,
 generating a positive relationship between range size and latitude
 (Rapoport's rule). However, this prediction fails to take into
 account the greater latitudinal extent of tropical temperatures relative
 to those at higher latitudes. Here we model the contributions of the
 broader latitudinal extent of equal-temperature habitats at low latitudes
 and the greater annual temperature variation at high latitudes to the
 range size–latitude relationship, and test whether the latitudinal
 variation in geographic range size in marine bivalves can be explained by
 models that account for both annual temperature variation and the
 steepness of latitudinal thermal gradients. Location: Western Pacific,
 eastern Pacific and western Atlantic. Methods: We use a null model where
 geographic ranges are placed on the ocean surface independently of thermal
 gradients, and a range-expansion model where the minimum and maximum
 temperatures encompassed by the geographic range of a species
 (macroecological thermal ranges) are positively related to annual
 temperature minima and maxima at the location where the species
 originated. We compare results with a database containing 40,820
 occurrences of 4760 marine bivalve species. Result: Models incorporating
 temperature-limited range expansion along realistic thermal gradients
 predict an inverse relationship between range size and latitude, in
 opposition to Rapoport's rule. The distribution patterns of marine
 bivalves match this prediction. Main conclusions: The poleward trend in
 latitudinal range size is determined by the nonlinearity of the
 latitudinal gradient of temperature minima and maxima and less by the
 latitudinal gradient of the local seasonal range in temperatures. Although
 tropical species do have narrower macroecological thermal ranges than
 high-latitude species, the nearly constant temperatures over wide areas of
 the tropics allow tropical species to achieve broad latitudinal ranges.
description: Range-shuffling model -
 shelf coordinates3 vectors with
 latitudinal coordinates and 3 corresponding vectors with longitudinal
 coordinates of 1° cells that include shelf depths &lt; 200 m for three
 ocean margins in the Western Pacific (allWPlats, allWPlongs), Eastern
 Pacific (allEPlats, allEPlongs), and Western Atlantic (allWAlats,
 allWAlongs). Midpoints of geographic ranges were assigned in the null
 model to these 1° cells.Shelf
 coordinates.RdataRange-shuffling model -
 SST gridded dataMODIS sea-surface
 temperature data (2009) in an array with 360 rows and 180 columns,
 corresponding to 1º cells (continental cells have NA values). These data
 were used in estimation of macroecological thermal ranges for species in
 the null model.SST gridded
 data.RdataRange-shuffling model -
 empirical species rangesEmpirical latitudinal
 and longitudinal ranges of species (in º) that are approximately conserved
 in the null model. These ranges are from the Western Atlantic (946
 species) and form two vectors - Slatextent and
 Slongextent.Empirical species
 ranges.RdataRange-shuffling model -
 locality coordinatesCoordinates and SST of sampled
 cells.RdataRange-shuffling
 model-source codeAppendix
 C.pdfRange expansion
 model-source codeAppendix
 B.pdfRange expansion
 model-gradients in SST in W AtlanticWA gradients in
 SST.RdataSpecies composition in
 the Western Pacific-5° lat. bandsPresence-absence data in
 the Western Pacific, with bivalve species in rows and 5° lat. bands in
 columnsSpecies composition in
 bands-WP.txtSpecies composition in
 the Eastern Pacific-5° lat. bandsPresence-absence data in
 the Eastern Pacific, with bivalve species in rows and 5° lat. bands in
 columnsSpecies composition in
 bands-EP.txtSpecies composition in
 the Western Atlantic-5° lat. bandsPresence-absence data in
 the Western Atlantic, with bivalve species in rows and 5° lat. bands in
 columnsSpecies composition in
 bands-WA.txt