Abstract
Climate forecasts project further increases in extremely high-temperature events. These present threats to biodiversity, as they promote population declines and local species extinctions. This implies that ecological communities will need to rely more strongly on recovery processes, such as recolonization from a meta-community context. It is poorly understood how differences in extreme event intensity change the outcome of subsequent community reassembly and if such extremes modify the biotic environment in ways that would prevent the successful re-establishment of lost species. We studied replicated aquatic communities consisting of algae and herbivorous rotifers in a design that involved a control and two different heat wave intensity treatments (29°C and 39°C). Animal species that suffered heat-induced extinction were subsequently re-introduced at the same time and density, in each of the two treatments. The 39°C treatment led to community closure in all replicates, meaning that a previously successful herbivore species could not re-establish itself in the postheat wave community. In contrast, such closure never occurred after a 29°C event. Heat wave intensity determined the number of herbivore extinctions and strongly affected algal relative abundances. Re-introduced herbivore species were thus confronted with significantly different food environments. This ecological legacy generated by heat wave intensity led to differences in the failure or success of herbivore species re-introductions. Reassembly was significantly more variable, and hence less predictable, after an extreme heat wave, and was more canalized after a moderate one. Our results pertain to relatively simple communities, but they suggest that ecological legacies introduced by extremely high-temperature events may change subsequent ecological recovery and even prevent the successful re-establishment of lost species. Knowing the processes promoting and preventing ecological recovery is crucial to the success of species re-introduction programs and to our ability to restore ecosystems damaged by environmental extremes.
Highlights
Under climate change major regions on the planet will experience both gradual warming and an increase in temperature variability
Ecology and Evolution published by John Wiley & Sons Ltd
Keratella declined by more than an order of magnitude in the first week, in the control, and in both heat wave treatments, we considered Keratella as a marginal species on its way to extinction; it was not reintroduced after its more rapid extinction in the extreme heat wave treatment
Summary
Under climate change major regions on the planet will experience both gradual warming and an increase in temperature variability. In the past three decades, such variability has already emerged in the form summertime extremely hot outliers (Hansen et al 2012). Variability in terms of environmental extremes poses a greater threat to species and biodiversity than slow and gradual warming itself (Vasseur et al 2014). Research has started to focus on gradual increases in mean temperatures (see Bale et al 2002; Brown et al 2004) and on the effects of increasingly severe extreme events (Jentsch et al 2007) such as heat waves (e.g., Sentis et al 2013) and other catastrophic climatic events such as floods
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