Resistance of Australian fish communities to drought and flood: implications for climate change and adaptations

Climate change induced extreme weather are dynamic in location, timing, and magnitude of rainfall and can alter how species respond to their environment. Extreme weather like droughts are now being seen as coupled to flooding when rainfall returns. Unfortunately, it is difficult to understand how ecological communities respond to the combination of drought and floods together. In the associated study we hypothesized that native organisms have evolved resistance to withstand repeated cycles of drought-flood disturbances, and that established non-native species have adapted to persist in novel conditions.

To test our hypothesis, we fit a geostatistical model of species occurrence with spatiotemporal local rainfall patterns as covariates in the drought and flood impacted Murray-Darling basin in Australia. The time range of this dataset included the decade long Millenium Drought, and its recovery period. During these drought conditions, river-floodplain organisms in the Murray-Darling became localized in refugia that limited longitudinal and lateral connectivity, and following flooding the same organisms were exposed to dispersal and recruitment opportunities, as well as to hypoxic blackwater events that lead to the mortality of aquatic organisms. At the basin-scale we found that the range size of most native and non-native fishes were highly resistant to the extreme drought and post-flood conditions. At local scales, species richness, or detection, actually increased under drought conditions. Both findings highlight the resistance of species to climate change driven extreme weather, which opens new questions on community adaptations.