DOI: 10.5061/dryad.23cn7
title: Data from: Decoupling of latitudinal gradients in species and genus geographic range size: a signature of clade range expansion

description: Aim. Clade range size is a function of species range sizes but also
 depends on the geographic deployment of species; clade range expansion
 should therefore depend partly on a clade’s tendency to produce new
 species. Under high speciation pressure, species-rich clades can migrate
 outside its present distribution, and thus overcome niche conservatism. A
 simple probabilistic mechanism for an out-of-tropics dynamic (OTT) for
 clade range expansion can thus operate in the absence of species-level
 differences in probability of range expansion, with speciation into novel
 climates more likely to occur in species-rich clades. In this scenario,
 (a) species and clade range sizes are decoupled and (b) clade range
 expansion is a function of per-clade species diversification. To test
 these predictions that can discriminate between a weaker and a stronger
 climatic niche conservatism, we contrast the latitudinal and thermal range
 sizes of marine bivalves at the species and clade (genus) level. Location.
 Western Pacific, Eastern Pacific, and Western Atlantic. Methods. We
 decompose the latitudinal and thermal distribution of genera into
 within-species and among-species dispersions and quantify their
 contributions to genus range size and species richness. We model the
 latitudinal gradient in per-genus species richness with a scenario where
 species range expansion does not vary with latitude. Result. Genus
 latitudinal range size cannot be predicted from the latitudinal range
 sizes of congeneric species, but strongly depends on latitudinal distances
 among species centroids, which correlate strongly with per-genus species
 richness. Genus thermal ranges correlate with the thermal ranges of
 congeneric species and thus support thermal conservatism of genera, but
 they correlate even more strongly with thermal differentiation among
 congeneric species. Genus latitudinal and thermal range sizes increase
 towards higher latitudes because genera that are species-rich anywhere
 within their range increase in proportion towards higher latitudes. Main
 Conclusions. The probabilistic model represents a first-order neutral
 expectation of clade-level range expansion at multiple phylogenetic levels
 arising from clade differences in net species diversification. Unless
 opposed by a strong niche conservatism, clade species richness can promote
 genus range expansion to new latitudes and climates. Species
 diversification thus plays a significant role in range expansion of marine
 genera even when thermal range sizes and limits of clades are conserved.
description: Data supplement-Western
 Pacific bivalve range limitsLatitudinal range limit
 of marine bivalve species in the Western Pacific living on continental or
 island shelves (water depths &lt; 200 m)Data supplement-Eastern
 Pacific bivalve range limitsLatitudinal range limit
 of marine bivalve species in the Eastern Pacific living on continental or
 island shelves (water depths &lt; 200 m)Data supplement-Western
 Atlantic bivalve range limitsLatitudinal range limit
 of marine bivalve species in the Western Atlantic living on continental or
 island shelves (water depths &lt; 200 m)Input objects-Western
 AtlanticThe input file for the R
 code for range expansion model. It has these objects: 3 objects - species,
 genera, genusnames - vectors of species names for 928 species, genus names
 for 390 genera, and genus names for each species, 2 objects - Slongextent,
 Slatextent - empirical latitudinal and longitudinal ranges in degrees for
 928 species, 2 objects - lats, longs - latitudes and longitudes of
 1-degree cells with species records in the Western Atlantic database, 3
 objects - shelflats, shelflongs, originationrates - latitudes and
 longitudes of all 1-degree cells in the Western Atlantic (shelf and island
 &lt; 200 m), and origination rates for each cell - based on temperature
 dependence of speciations, using mean sea-surface temperature for each
 cellRange_expansion_model-Western AtlanticSource code for range expansion model in R language, using input data from the Western Atlantic