Temperature and biodiversity influence community stability differently in birds and fishes.

Determining the factors that affect community stability is crucial to understanding the maintenance of biodiversity and ecosystem functioning in the face of global warming. We investigated how four temperature components (that is, median, variability, trend and extremes) affected diversity-synchrony-stability relationships for 1,246 bird and 580 fish communities from temperate regions. We hypothesized a stabilizing effect on the community if the variation in species' response to changing median temperature decreases overall community synchrony (hypothesis H1) and if temperature extremes reduce interspecific synchrony at extreme abundances due to variation in species' thermal tolerance limits (hypothesis H2). We found support for H1 in fish and for H2 in bird communities. Here we showed that the abiotic components (that is, the median, variability, trend and extremes of temperature) had more indirect effects on community stability, predominantly by affecting the biotic components (that is, diversity, synchrony). Considering various temperature components' direct as well as indirect impacts on stability for terrestrial versus aquatic communities will improve our mechanistic understanding of biodiversity change in response to global climatic stressors.

Temporal turnover in species' ranks can explain variation in Taylor's slope for ecological timeseries.

The scaling exponent relating the mean and variance of the density of individual organisms in space (i.e., Taylor's slope: zspace) is well studied in ecology, but the analogous scaling exponent for temporal datasets (ztime) is underdeveloped. Previous theory suggests the narrow distribution of ztime (e.g., typically 1-2) could be due to interspecific competition. Here, using 1694 communities time series, we show that ztime can exceed 2, and reaffirm how this can affect our inference about the stabilizing effect of biodiversity. We also develop a new theory, based on temporal change in the ranks of species abundances, to help account for the observed ztime distribution. Specifically, we find that communities with minimal turnover in species' rank abundances are more likely to have higher ztime. Our analysis shows how species-level variability affects our inference about the stability of ecological communities.

Warming underpins community turnover in temperate freshwater and terrestrial communities.

Rising temperatures are leading to increased prevalence of warm-affinity species in ecosystems, known as thermophilisation. However, factors influencing variation in thermophilisation rates among taxa and ecosystems, particularly freshwater communities with high diversity and high population decline, remain unclear. We analysed compositional change over time in 7123 freshwater and 6201 terrestrial, mostly temperate communities from multiple taxonomic groups. Overall, temperature change was positively linked to thermophilisation in both realms. Extirpated species had lower thermal affinities in terrestrial communities but higher affinities in freshwater communities compared to those persisting over time. Temperature change's impact on thermophilisation varied with community body size, thermal niche breadth, species richness and baseline temperature; these interactive effects were idiosyncratic in the direction and magnitude of their impacts on thermophilisation, both across realms and taxonomic groups. While our findings emphasise the challenges in predicting the consequences of temperature change across communities, conservation strategies should consider these variable responses when attempting to mitigate climate-induced biodiversity loss.