Climate‐driven, but dynamic and complex? A reconciliation of competing hypotheses for species’ distributionsSchultz, Emily L.; Hülsmann, Lisa; Pillet, Michiel D.; Hartig, Florian; Breshears, David D.; Record, Sydne; Shaw, John D.; DeRose, R. Justin; Zuidema, Pieter A.; Evans, Margaret E. K.; Chase, Jonathan
doi: 10.1111/ele.13902pmid: 34708503
Estimates of the percentage of species “committed to extinction” by climate change range from 15% to 37%. The question is whether factors other than climate need to be included in models predicting species’ range change. We created demographic range models that include climate vs. climate‐plus‐competition, evaluating their influence on the geographic distribution of Pinus edulis, a pine endemic to the semiarid southwestern U.S. Analyses of data on 23,426 trees in 1941 forest inventory plots support the inclusion of competition in range models. However, climate and competition together only partially explain this species’ distribution. Instead, the evidence suggests that climate affects other range‐limiting processes, including landscape‐scale, spatial processes such as disturbances and antagonistic biotic interactions. Complex effects of climate on species distributions—through indirect effects, interactions, and feedbacks—are likely to cause sudden changes in abundance and distribution that are not predictable from a climate‐only perspective.
Towards revealing the global diversity and community assembly of soil eukaryotesAslani, Farzad; Geisen, Stefan; Ning, Daliang; Tedersoo, Leho; Bahram, Mohammad; Vries, Franciska
doi: 10.1111/ele.13904pmid: 34697894
Soil fungi, protists, and animals (i.e., the eukaryome) play a critical role in key ecosystem functions in terrestrial ecosystems. Yet, we lack a holistic understanding of the processes shaping the global distribution of the eukaryome. We conducted a molecular analysis of 193 composite soil samples spanning the world's major biomes. Our analysis showed that the importance of selection processes was higher in the community assemblage of smaller‐bodied and wider niche breadth organisms. Soil pH and mean annual precipitation were the primary determinants of the community structure of eukaryotic microbes and animals, respectively. We further found contrasting latitudinal diversity patterns and strengths for soil eukaryotic microbes and animals. Our results point to a potential link between body size and niche breadth of soil eukaryotes and the relative effect of ecological processes and environmental factors in driving their biogeographic patterns.
Habitat percolation transition undermines sustainability in social‐ecological agricultural systemsBengochea Paz, Diego; Henderson, Kirsten; Loreau, Michel; He, Fangliang
doi: 10.1111/ele.13914pmid: 34747112
Steady increases in human population size and resource consumption are driving rampant agricultural expansion and intensification. Habitat loss caused by agriculture puts the integrity of ecosystems at risk and threatens the persistence of human societies that rely on ecosystem services. We develop a spatially explicit model describing the coupled dynamics of an agricultural landscape and human population size to assess the effect of different land‐use management strategies, defined by agricultural clustering and intensification, on the sustainability of the social‐ecological system. We show how agricultural expansion can cause natural habitats to undergo a percolation transition leading to abrupt habitat fragmentation that feedbacks on human's decision making, aggravating landscape degradation. We found that agricultural intensification to spare land from conversion is a successful strategy only in highly natural landscapes, and that clustering agricultural land is the most effective measure to preserve large connected natural fragments, prevent severe fragmentation and thus, enhance sustainability.
Sampling bias exaggerates a textbook example of a trophic cascadeBrice, Elaine M.; Larsen, Eric J.; MacNulty, Daniel R.; Coulson, Tim
doi: 10.1111/ele.13915pmid: 34748261
Understanding trophic cascades in terrestrial wildlife communities is a major challenge because these systems are difficult to sample properly. We show how a tradition of non‐random sampling has confounded this understanding in a textbook system (Yellowstone National Park) where carnivore [Canis lupus (wolf)] recovery is associated with a trophic cascade involving changes in herbivore [Cervus canadensis (elk)] behaviour and density that promote plant regeneration. Long‐term data indicate a practice of sampling only the tallest young plants overestimated regeneration of overstory aspen (Populus tremuloides) by a factor of 4–7 compared to random sampling because it favoured plants taller than the preferred browsing height of elk and overlooked non‐regenerating aspen stands. Random sampling described a trophic cascade, but it was weaker than the one that non‐random sampling described. Our findings highlight the critical importance of basic sampling principles (e.g. randomisation) for achieving an accurate understanding of trophic cascades in terrestrial wildlife systems.