Ecology Letters

Bowler, Catherine H.; Weiss‐Lehman, Christopher; Towers, Isaac R.; Mayfield, Margaret M.; Shoemaker, Lauren G.; Enquist, Brian

doi: 10.1111/ele.14011pmid: 35633300

Natural systems contain more complexity than is accounted for in models of modern coexistence theory. Coexistence modelling often disregards variation arising from stochasticity in biological processes, heterogeneity among individuals and plasticity in trait values. However, these unaccounted‐for sources of uncertainty are likely to be ecologically important and have the potential to impact estimates of coexistence. We applied a Bayesian modelling framework to data from an annual plant community in Western Australia to propagate uncertainty in coexistence outcomes using the invasion criterion and ratio of niche to fitness differences. We found accounting for this uncertainty altered predictions of coexistence versus competitive exclusion for 3 out of 14 species pairs and yielded a probability of priority effects for an additional species pair. The propagation of uncertainty arising from sources of biological complexity improves our ability to predict coexistence more accurately in natural systems.

Fragata, Inês; Costa‐Pereira, Raul; Kozak, Mariya; Majer, Agnieszka; Godoy, Oscar; Magalhães, Sara; Angert, Amy

doi: 10.1111/ele.14021pmid: 35596732

Historical contingency, such as the order of species arrival, can modify competitive outcomes via niche modification or pre‐emption. However, how these mechanisms ultimately modify stabilising niche and average fitness differences remains largely unknown. By experimentally assembling two congeneric spider mite species feeding on tomato plants during two generations, we show that order of arrival affects species’ competitive ability and changes the outcome of competition. Contrary to expectations, order of arrival did not cause positive frequency dependent priority effects. Instead, coexistence was predicted when the inferior competitor (Tetranychus urticae) arrived first. In that case, T. urticae colonised the preferred feeding stratum (leaves) of T. evansi leading to spatial niche pre‐emption, which equalised fitness and reduced niche differences, driving community assembly to a close‐to‐neutrality scenario. Our study demonstrates how the order of species arrival and the spatial context of competitive interactions may jointly determine whether species can coexist.

Fay, Rémi; Hamel, Sandra; Pol, Martijn; Gaillard, Jean‐Michel; Yoccoz, Nigel G.; Acker, Paul; Authier, Matthieu; Larue, Benjamin; Le Coeur, Christie; Macdonald, Kaitlin R.; Nicol‐Harper, Alex; Barbraud, Christophe; Bonenfant, Christophe; Van Vuren, Dirk H.; Cam, Emmanuelle; Delord, Karine; Gamelon, Marlène; Moiron, Maria; Pelletier, Fanie;

Yang, Xianyu; Angert, Amy L.; Zuidema, Pieter A.; He, Fangliang; Huang, Shongming; Li, Shouzhong; Li, Shou‐Li; Chardon, Nathalie I.; Zhang, Jian; Levine, Jonathan

doi: 10.1111/ele.14028pmid: 35598109

Demographic compensation—the opposing responses of vital rates along environmental gradients—potentially delays anticipated species’ range contraction under climate change, but no consensus exists on its actual contribution. We calculated population growth rate (λ) and demographic compensation across the distributional ranges of 81 North American tree species and examined their responses to simulated warming and tree competition. We found that 43% of species showed stable population size at both northern and southern edges. Demographic compensation was detected in 25 species, yet 15 of them still showed a potential retraction from southern edges, indicating that compensation alone cannot maintain range stability. Simulated climatic warming caused larger decreases in λ for most species and weakened the effectiveness of demographic compensation in stabilising ranges. These findings suggest that climate stress may surpass the limited capacity of demographic compensation and pose a threat to the viability of North American tree populations.

Miller, Zachary R.; Lechón‐Alonso, Pablo; Allesina, Stefano; Ostling, Annette

doi: 10.1111/ele.14027pmid: 35635769

Plant–soil feedbacks (PSFs) are considered a key mechanism generating frequency‐dependent dynamics in plant communities. Negative feedbacks, in particular, are often invoked to explain coexistence and the maintenance of diversity in species‐rich communities. However, the primary modelling framework used to study PSFs considers only two plant species, and we lack clear theoretical expectations for how these complex interactions play out in communities with natural levels of diversity. Here, we extend this canonical model of PSFs to include an arbitrary number of plant species and analyse the dynamics. Surprisingly, we find that coexistence of more than two species is virtually impossible, suggesting that alternative theoretical frameworks are needed to describe feedbacks observed in diverse natural communities. Drawing on our analysis, we discuss future directions for PSF models and implications for experimental study of PSF‐mediated coexistence in the field.