Data from: Explaining global variation in the latitudinal diversity gradient: meta-analysis confirms known patterns and uncovers new ones

Aim: The pattern of increasing biological diversity from high latitudes to
the equator [latitudinal diversity gradient (LDG)] has been recognized for
> 200 years. Empirical studies have documented this pattern across
many different organisms and locations. Our goal was to quantify the
evidence for the global LDG and the associated spatial, taxonomic and
environmental factors. We performed a meta-analysis on a large number of
individual LDGs that have been published in the 14 years since
Hillebrand's ground-breaking meta-analysis of the LDG, using
meta-analysis and meta-regression approaches largely new to the fields of
ecology and biogeography. Location: Global. Time period: January
2003–September 2015. Major taxa studied: Bacteria, protists, plants, fungi
and animals. Methods: We synthesized the outcomes of 389 individual cases
of LDGs from 199 papers published since 2003, using hierarchical
mixed-effects meta-analysis and multiple meta-regression. Additionally, we
re-analysed Hillebrand's original dataset using modern methods.
Results: We confirmed the generality of the LDG, but found the pattern to
be weaker than was found in Hillebrand's study. We identified
previously unreported variation in LDG strength and slope across
longitude, with evidence that the LDG is strongest in the Western
Hemisphere. Locational characteristics, such as habitat and latitude
range, contributed significantly to LDG strength, whereas organismal
characteristics, including taxonomic group and trophic level, did not.
Modern meta-analytical models that incorporate hierarchical structure led
to more conservative and sometimes contrasting effect size estimates
relative to Hillebrand's initial analysis, whereas meta-regression
revealed underlying patterns in Hillebrand's dataset that were not
apparent with a traditional analysis. Main conclusions: We present
evidence of global latitudinal, longitudinal and habitat-based patterns in
the LDG, which are apparent across both marine and terrestrial realms and
over a broad taxonomic range of organisms, from bacteria to plants and
vertebrates.