Abstract
AbstractAimThis work explores whether the commonly observed positive range size–niche breadth relationship exists for Fagus, one of the most dominant and widespread broad‐leaved deciduous tree genera in temperate forests of the Northern Hemisphere. Additionally, we ask whether the 10 extant Fagus species’ niche breadths and climatic tolerances are under phylogenetic control.LocationNorthern Hemisphere temperate forests.TaxonFagus L.MethodsCombining the global vegetation database sPlot with Chinese vegetation data, we extracted 107,758 relevés containing Fagus species. We estimated biotic and climatic niche breadths per species using plot‐based co‐occurrence data and a resource‐based approach, respectively. We examined the relationships of these estimates with range size and tested for their phylogenetic signal, prior to which a Random Forest (RF) analysis was applied to test which climatic properties are most conserved across the Fagus species.ResultsNeither biotic niche breadth nor climatic niche breadth was correlated with range size, and the two niche breadths were incongruent as well. Notably, the widespread North American F. grandifolia had a distinctly smaller biotic niche breadth than the Chinese Fagus species (F. engleriana, F. hayatae, F. longipetiolata and F. lucida) with restricted distributions in isolated mountains. The RF analysis revealed that cold tolerance did not differ among the 10 species, and thus may represent an ancestral, fixed trait. In addition, neither biotic nor climatic niche breadths are under phylogenetic control.Main ConclusionsWe interpret the lack of a general positive range size–niche breadth relationship within the genus Fagus as a result of the widespread distribution, high among‐region variation in available niche space, landscape heterogeneity and Quaternary history. The results hold when estimating niche sizes either by fine‐scale co‐occurrence data or coarse‐scale climate data, suggesting a mechanistic link between factors operating across spatial scales. Besides, there was no evidence for diverging ecological specialization within the genus Fagus.
Highlights
Geographical range size is generally defined as the 2-dimensional extent of the spatial distribution of a species based on latitudinal and longitudinal extents (Gaston, 1991), whereas a species’ realized niche is widely understood as the n-dimensional hypervolume (Hutchinson, 1957) defined by the multi-dimensional range of abiotic and biotic conditions under which it can sustain natural populations (Blonder, 2018)
| 9 et al, 2012; Brown, 1984; Kambach et al, 2019; Sheth et al, 2020; Slatyer et al, 2013), we found no significant relationship between range size and the biotic and climatic niche breadth estimates for the species in the globally important tree genus Fagus
The Fagus species in Korea (F. multinervis) and Japan (F. crenata and F. japonica) have narrower biotic and climatic niche breadth, consistent with these species being limited to isolated islands, especially for F. multinervis, endemic to Ulleungdo Island (Hukusima et al, 2013)
Summary
Geographical range size is generally defined as the 2-dimensional extent of the spatial distribution of a species based on latitudinal and longitudinal extents (Gaston, 1991), whereas a species’ realized niche is widely understood as the n-dimensional hypervolume (Hutchinson, 1957) defined by the multi-dimensional range of abiotic and biotic conditions under which it can sustain natural populations (Blonder, 2018). A meta-analysis of 64 studies worldwide, found widespread convergence between geographical range size and niche breadth, even after taking into account differences in niche breadth measurements, taxonomic groups, spatial scales and sampling effects across studies (Slatyer et al, 2013). This has raised concerns for specialist species that might be disproportionally affected by habitat loss (Staude et al, 2020). Contrasting patterns have been observed (Kambach et al, 2019; Slatyer et al, 2013), potentially reflecting the multitude of factors affecting range size and realized niche breadth, such as dispersal abilities, regional availability of suitable niche space and historical events
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