DOI: 10.5061/dryad.gb5mkkwqf
title: Data & R code for: Paquette & Hargreaves 'Biotic interactions are more often important at species' warm vs. cool range edges'

description: Predicting which ecological factors constrain species distributions is a
 fundamental ecological question and critical to forecasting geographic
 responses to global change. Darwin hypothesized that abiotic factors
 generally impose species’ high-latitude and high-elevation (typically
 cool) range limits, whereas biotic interactions more often impose species’
 low-latitude/low-elevation (typically warm) limits, but empirical support
 has been mixed. Here, we clarify three predictions arising from Darwin’s
 hypothesis, and show that previously mixed support is partially due to
 researchers testing different predictions. Using a comprehensive
 literature review (885 range limits), we find that biotic interactions,
 including competition, predation, and parasitism, contributed to
 &gt;60% of range limits, and influenced species’ warm limits more
 often than cool limits. Abiotic factors contributed more often than biotic
 interactions to cool range limits, but temperature contributed frequently
 to both cool and warm limits. Our results suggest that most range limits
 will be sensitive to climate warming, but warm-limit responses will depend
 strongly on biotic interactions.
description: There are two sets of data: data on potentially range-limiting
 factors (one file for cool limits and one file for warm limits), and data
 for locations of each data point (again, one file for cool limits, one for
 warm limits). See Supplementary Materials for full
 description. In brief: We searched Web of Science for
 studies published up to the end of 2019 that assessed the causes of
 species’ high latitude/elevation (hereafter ‘cool’) or low
 latitude/elevation (hereafter ‘warm’) range limits. To increase coverage
 in areas with few studies, we repeated the search in Spanish and French
 and did a targeted search for studies from Africa. We screened results for
 studies that assessed the importance of at least one biotic or abiotic
 factor in causing a cool or warm range limit. We
 extracted data for each potentially range-limiting factor assessed,
 separating data by study and species whenever possible. For each study x
 taxon x range limit (latitude or elevation, cool or warm, separated by
 continent or ocean if applicable), we identified the potential
 range-limiting factors assessed, such that each factor a study assessed at
 a given range limit contributed 1 data point.  We noted whether each
 factor was biotic or abiotic (‘factor type’) and what category of factor
 it was.  Multiple assessments of a factor category (e.g. max. and mean
 annual temperature) at one species’ range limit would contribute one data
 point.  Factors outside these categories were assigned as
 ‘other’. We collected various meta-data about each data
 point, as explained in the 'column headings explained'
 sheet. We assessed whether each factor contributed to
 the given range limit (‘yes’ or ‘no’), determined from statistical
 results, figures, and author arguments when necessary. Data and reasoning
 behind these decisions are given in separate columns. If a study
 considered &gt;1 measure of one factor (e.g. summer and winter
 temperature), we deemed the factor (temperature in this example) supported
 if any measure contributed to the range limit.  For studies in Cahill et
 al. (2014), we used their conclusions unless a) data were grouped across
 species or studies, in which case we ungrouped data and reassessed
 conclusions for each species/study, or b) we spot checked the study and
 could not find evidence to support the conclusion.  These decisions are
 also detailed in the data.