All ecological disciplines consider temporal dynamics, although relevant concepts have been developed almost independently. We here introduce basic principles of temporal dynamics in ecology. We figured out essential features that describe temporal dynamics by finding similarities among about 60 ecological concepts and theories. We found that considering the hierarchically nested structure of complexity in temporal patterns (i.e. hierarchical complexity) can well describe the fundamental nature of temporal dynamics by expressing which patterns are observed at each scale. Across all ecological levels, driver-response relationships can be temporally variant and dependent on both shortand long-term past conditions. The framework can help with designing experiments, improving predictive power of statistics, and enhancing communications among ecological disciplines. The Need for Basic Principles of Temporal DynamicsAll ecological disciplines consider temporal dynamics with major paradigms shifting from one to another: equilibrium (see Glossary) to nonequilibrium, and stationary to nonstationary (Box 1). Understanding temporal dynamics is becoming more important in the Anthropocene. Several time-related concepts and statistics have emerged recently [1][2][3][4]. Nevertheless, ecology still lacks basic principles that underlie all studies relevant to temporal dynamics [5], and the exchange of knowledge about temporal dynamics among subdisciplines is limited [6,7].Recently developed concepts include, for example, temporal ecology [5], abrupt shifts in ecological systems [8], ecological memory [3], lag hypothesis for community dynamics [9], and asymptotic environmentally determined trajectories [1]. These were proposed almost independently of each other. However, they all consider that driver-response relationships are not necessarily constant through time, but they depend on the recent and historical past. This perspective brings together various concepts to figure out the essence of temporal dynamics across ecological and temporal scales. HighlightsTemporal dynamics are inherently complex.Concepts and techniques have flourished to understand ecological temporal dynamics in recent years.A key finding of recent studies is that driver-response relationships are not necessarily constant through time, but rather, that they are conditioned by the recent and historical past.Basic principles of temporal dynamics need to be summarized to increase the understanding and predictability of complex temporal dynamics in ecology and evolution.

The rate of change (RoC) of environmental drivers matters: biotic and abiotic components respond differently when faced with a fast or slow change in their environment. This phenomenon occurs across spatial scales and thus levels of ecological organization. We investigated the RoC of environmental drivers in the ecological literature and examined publication trends across ecological levels, including prevalent types of evidence and drivers. Research interest in environmental driver RoC has increased over time (particularly in the last decade), however, the amount of research and type of studies were not equally distributed across levels of organization and different subfields of ecology use temporal terminology (e.g. ‘abrupt’ and ‘gradual’) differently, making it difficult to compare studies. At the level of individual organisms, evidence indicates that responses and underlying mechanisms are different when environmental driver treatments are applied at different rates, thus we propose including a time dimension into reaction norms. There is much less experimental evidence at higher levels of ecological organization (i.e. population, community, ecosystem), although theoretical work at the population level indicates the importance of RoC for evolutionary responses. We identified very few studies at the community and ecosystem levels, although existing evidence indicates that driver RoC is important at these scales and potentially could be particularly important for some processes, such as community stability and cascade effects. We recommend shifting from a categorical (e.g. abrupt versus gradual) to a quantitative and continuous (e.g. °C/h) RoC framework and explicit reporting of RoC parameters, including magnitude, duration and start and end points to ease cross‐scale synthesis and alleviate ambiguity. Understanding how driver RoC affects individuals, populations, communities and ecosystems, and furthermore how these effects can feed back between levels is critical to making improved predictions about ecological responses to global change drivers. The application of a unified quantitative RoC framework for ecological studies investigating environmental driver RoC will both allow cross‐scale synthesis to be accomplished more easily and has the potential for the generation of novel hypotheses.

Summary A recent study by Sugiura and coworkers reported the non‐symbiotic growth and spore production of an arbuscular mycorrhizal (AM) fungus, Rhizophagus irregularis, when the fungus received an external supply of certain fatty acids, myristates (C:14). This discovery follows the insight that AM fungi receive fatty acids from their hosts when in symbiosis. If this result holds up and can be repeated under nonsterile conditions and with a broader range of fungi, it has numerous consequences for our understanding of AM fungal ecology, from the level of the fungus, at the plant community level, and to functional consequences in ecosystems. In addition, myristate may open up several avenues from a more applied perspective, including improved fungal culture and supplementation of AM fungi or inoculum in the field. We here map these potential opportunities, and additionally offer thoughts on potential risks of this potentially new technology. Lastly, we discuss the specific research challenges that need to be overcome to come to an understanding of the potential role of myristate in AM ecology.

No abstract