Widespread underfilling of the potential ranges of North American trees

Abstract

Aim Climatic equilibrium is a foundational principle in ecological theory and models used in conservation, but has been challenged by growing evidence of disequilibrium, particularly for long‐lived, sessile organisms like trees. Here, we calculated range filling for North American trees to detect the degree to which trees are filling their potential climatic niches, and to assess climatic and non‐climatic drivers of underfilling. Location North America (22°N–72°N). Taxon Trees and shrubs. Methods We modelled the potential ranges of 447 North American tree and shrub species with species distribution models using bioclimatic variables, and calculated the occupied proportion of each potential range. Results were compared to a null model using simulated ranges generated by a spreading‐dye algorithm. We further used range shape ratios (latitude/longitude) to detect the drivers of disequilibrium. Results The potential ranges of North American trees and shrubs are broadly underfilled (mean = 48%). Furthermore, range filling is positively correlated with geographic range size. Large‐ranged species have higher range filling than the null model, and shape ratios indicative of climatic restrictions. Small‐ranged species showed a stronger influence of dispersal limitation. Main conclusions Climate explains only about half of tree species' ranges, and the signal of climatic equilibrium increases with range size. Small‐range species show high levels of climatic disequilibrium, which is likely be driven by combinations of dispersal lags, and undetected environmental factors or biotic interactions. These results highlight the importance of conserving small‐ranged species and the difficulty of forecasting how their distributions will shift in the coming centuries.

Of mutualism and migration: will interactions with novel ericoid mycorrhizal communities help or hinder northward Rhododendron range shifts?

“…Bellemare and Moeller 2014; Fig. 1b) (Seliger et al 2021). The survival of planted R. catawbiense in horticulture in the region, and records of occasional adventive R. catawbiense individuals growing near areas of human habitation in southern New England (Haines 2011), suggest aspects of its ecological niche requirements are already sometimes met in the region.…”

Human food use increases plant geographical ranges in the Sonoran Desert

“…Although there is general consensus that both environmental filtering (i.e., abiotic constraints) and dispersal (e.g., chance colonization, differences in dispersal abilities) play a role in community assembly and distribution dynamics (Fraaije et al., 2015; Guo et al., 2005), our research suggests that past human‐mediated dispersal of food plants is also a major driver of community assembly and distribution dynamics. However, the relatively low explained variation in the statistical models indicates that human use is not the only factor explaining range‐filling patterns; for example, as seen in North American trees (Seliger et al., 2021). Our results, therefore, provide an alternative and complementary explanation for previously described patterns of range filling (e.g., Seliger et al., 2021; Svenning & Sandel, 2013; Svenning & Skov, 2004) and build on prior studies of biogeographical consequences of human dispersal of plants (Abrams & Nowacki, 2008; Van Zonneveld et al., 2018; Warren, 2016) to provide flora‐wide analyses and to carry out these analyses in an arid biome.…”

“…However, the relatively low explained variation in the statistical models indicates that human use is not the only factor explaining range‐filling patterns; for example, as seen in North American trees (Seliger et al., 2021). Our results, therefore, provide an alternative and complementary explanation for previously described patterns of range filling (e.g., Seliger et al., 2021; Svenning & Sandel, 2013; Svenning & Skov, 2004) and build on prior studies of biogeographical consequences of human dispersal of plants (Abrams & Nowacki, 2008; Van Zonneveld et al., 2018; Warren, 2016) to provide flora‐wide analyses and to carry out these analyses in an arid biome.…”

Effects of climate and topography on the diversity anomaly of plants disjunctly distributed in eastern Asia and eastern North America

“…These ice sheets constrained the extent of suitable habitat for plants and hampered the geographic shifting of plant distributions. Plant species in ENA likely dispersed slowly, with relatively low post‐glacial migration rates, and did not reach equilibrium with climate (Seliger et al., 2021), as was also the case in Europe (Svenning & Skov, 2004, 2005, 2007). In contrast, eastern Asia lacked large‐scale ice sheets, although permafrost covered Asia south to 40° N (Beijing area; Rapp, 2012).…”