Table 1.

Summary of hypotheses and models on the causes of range limits

Hypothesis/model	Category	Premise of hypothesis/model	Relevant taxa	Notable papers
Species distribution models/environmental niche models/climate envelope models	Abiotic	These models assume that animals and plants track a climate niche, i.e., their distributions are their fundamental niche. They are commonly used to evaluate abiotic constraints on species' distributions and to generate predictive maps.	Plants and animals	Pearson and Dawson (2003), Soberón (2007)
Climatic variability hypothesis	Abiotic	This hypothesis posits that species are more temperature limited in aseasonal environments and have narrow temperature niches than species living in seasonal and harsher climates, which explains narrower altitudinal distributions in tropical areas.	Plants and animals	Janzen (1967), Ghalambor, Huey, Martin, Tewksbury, & Wang (2006)
Abundant‐centre model/abundant‐centre hypothesis/Central margin hypothesis/Centre‐periphery hypothesis	Biotic	These hypotheses and models predict that abundance, fitness, or genetic diversity is highest at the centre of a species geographical range and declines towards each edge.	Plants and animals	Brown (1984), Gaston et al. (2000), Carter and Prince (1981), Pironon et al. (2017)
Asymmetric abiotic stress limitation hypothesis (AASL); species interactions‐abiotic stress hypothesis (SIASH); Stress‐trade‐off hypothesis (STH)	Abiotic or biotic	These contributions are centred around the classic hypothesis described by Darwin (1859), Connell (1961), Dobzhansky (1950) and MacArthur (1984), which posits that abiotic factors form high‐latitude/altitude limits and biotic interactions form lower limits.	Plants and animals	Darwin (1859), Dobzhansky (1950), Connell (1961), MacArthur (1984), Normand et al. (2009), Louthan et al. (2015), Anderegg and HilleRisLambers (2019)
Stress‐gradient hypothesis (SGH)	Interactive	This hypothesis postulates that gradients of environmental stress determine the extent to which competition affects populations. Those living along lower edges, in less stressful environments, are more likely to experience competition, whereas those along upper edges, where abiotic stress is thought to be higher, are more likely to experience positive biotic interactions (e.g. facilitation).	Plants	Callaway et al. (2002), Ettinger and HilleRisLambers (2017)
Condition‐specific competition (CSC); resource availability hypothesis	Interactive	The main premise of this hypothesis is that interacting species will either gain or lose competitive advantage based on environmental conditions and this will, in turn, affect their distributions.	Animals	Connell (1961), Taniguchi & Nakano (2000), Malenke et al. (2011), Srinivasan et al. (2018)