Code and data from: Global patterns in plant environmental breadths

The latitudinal gradient in plant diversity is one of the most famous
patterns in ecology. It is hypothesised that narrow niche breadths and
restricted geographic ranges in the tropics allow more species to coexist
with minimal overlap, relative to high-latitude regions. Although a wealth
of studies have investigated these questions across different regions and
taxonomic groups, these have consistently yielded contradictory results,
leading to the continued persistence of numerous ecological explanations.
Here, using a global occurrence database containing over 100,000 plant
species, we provide the first globally standardised investigation into the
geographic relationships among latitudinal range, environmental breath,
and latitudinal median. We find limited evidence for a global latitudinal
gradient in species’ ranges and environmental breadths, with results
varying between hemispheres and along latitude within each hemisphere. In
agreement with previous observations, we show consistent support for a
latitudinal gradient in environmental breadth and latitudinal range, but
only for trees in the northern hemisphere and for tropical species. In the
southern hemisphere, conversely, these trends are inverted for
non-tropical species, with latitudinal range and environmental breadth
decreasing with distance from the equator. Moreover, these relationships
are even weaker with environmental breadth, even though there is a strong
relationship between environmental breadth and latitudinal range. By
applying standardised methods at the global scale, these results
illustrate that variation in species’ ranges is largely a by-product of
biogeographic patterns rather than niche processes. Collectively, this
work suggests that existing ecological “rules” linking niche breadth to
latitude predominantly reflect regional sampling biases and a historical
focus on the northern hemisphere and certain taxonomic groups.