DOI: 10.5061/dryad.sb175
title: Data from: Environmental harshness is positively correlated with intraspecific divergence in mammals and birds

description: Life on Earth is conspicuously more diverse in the tropics. Although this
 intriguing geographical pattern has been linked to many biotic and abiotic
 factors, their relative importance and potential interactions are still
 poorly understood. The way in which latitudinal changes in ecological
 conditions influence evolutionary processes is particularly controversial,
 as there is evidence for both a positive and a negative latitudinal
 gradient in speciation rates. Here, we identify and address some
 methodological issues (how patterns are analysed and how latitude is
 quantified) that could lead to such conflicting results. To address these
 issues, we assemble a comprehensive data set of the environmental
 correlates of latitude (including climate, net primary productivity and
 habitat heterogeneity) and combine it with biological, historical and
 molecular data to explore global patterns in recent divergence events
 (subspeciation). Surprisingly, we find that the harsher conditions that
 typify temperate habitats (lower primary productivity, decreased rainfall
 and more variable and unpredictable temperatures) are positively
 correlated with greater subspecies richness in terrestrial mammals and
 birds. Thus, our findings indicate that intraspecific divergence is
 greater in regions with lower biodiversity, a pattern that is robust to
 both sampling variation and latitudinal biases in taxonomic knowledge. We
 discuss possible causal mechanisms for the link between environmental
 harshness and subspecies richness (faster rates of evolution, greater
 likelihood of range discontinuities and more opportunities for divergence)
 and conclude that this pattern supports recent indications that
 latitudinal gradients of diversity are maintained by simultaneously higher
 potentials for both speciation and extinction in temperate than tropical
 regions.
description: Data4DryadCSV file with 1 header line, 26 columns, and 9830 rows of data. Data collated from literature reviews (sources cited in the main text or in column 23). Version 2 of this data set corrects a scaling issue in the original column 18 (that is, ca. 2% of the originally reported values for BREEDING.RANGE.AREA were reported in m2 rather than km2). V2 also provides recomputed values for the composite variables derived from principal components analysis (cols. 19-22). PLEASE NOTE THAT: (i) All original values can still be accessed through v1; and (ii) this minor correction does not affect qualitatively the findings reported in our MEC paper. ABBREVIATIONS and UNITS: DISSECTED.BY.MOUNTAINS = True if breeding range is divided into two or more isolated regions by a mountain chain; LAT.RANGE = Latitudinal range; ENV.SHIELDING = Environmental shielding (1 = migratory bird or hibernating mammal); GLACIATION: 1= 20% or more of current breeding range overlap with areas glaciated in the last 21,000 years; ISLAND.DWELLING: 1 = 20% or more of the breeding range occurs on islands; HABITAT.HETEROGENEITY: number of biomes covering at least 5% of the breeding range; BODY.SIZE: Adult body size in grams; PRECIP = Precipitation (in mm); TEMP = Temperature (in degrees Celsius); NPP = Net Primary Productivity (in log10[ g carbon per yr ] ); BREEDING.RANGE.AREA = Area of the breeding distribution (in km2); ENV.HARSHNESS = Environmental harshness (Raw values for PC1); GEOGRAPHIC.COVERAGE = Raw values for PC2; RAINFALL.UNPREDICTABILITY = Raw values for PC3; RESIDUAL.BODY.SIZE = Raw Values for PC4; N.MOST.LAT = Northernmost latitude in the breeding range; S.MOST.LAT = Southernmost latitude in the breeding range; CENTROID = centroid latitude for the breeding range.