Natural microcosms are bellwether model systems in ecology and evolutionary biology especially under climate change

Abstract Natural microcosms are those such as galls, flowers, splashpools and lichen patches that form uniquely circumscribed systems, whose boundaries may be difficult to physically and physiologically define. Yet, unlike artificial microcosms that are assembled within petri plates, outdoor or indoor tanks, natural microcosms contain a full complement of organismal diversity within intricate food webs thus constituting functional natural ecosystems. Their small size and smaller number of organisms inhabiting them make many natural microcosms amenable to experimentation and utilization of techniques including sophisticated labelling, stoichiometry, genomics and transcriptomics to answer fundamental aspects of species ecology, ecosystem functioning, nutrient flows and physiological responses to climate change. Many natural microcosms of the same type occur over wide latitudinal extents and can therefore be used to investigate large-scale climatic impacts. Some microcosms exhibit internal gradients of temperature and oxygenation saturation resulting in different abiotic conditions within microcosms. Thus, an individual microcosm type can offer insights into physiological adaptations such as thermal tolerance. Organisms that inhabit ephemeral microcosms must also have efficient dispersal or dormancy strategies contributing to organism survival. The ephemerality of the microcosm may contribute to organism specialization versus generalization. Microlandscape ecology and microcosm stoichiometry are other new research areas that microcosms offer. This article is part of the theme issue ‘Life in natural microcosms’.