Are extreme high temperatures at low or high latitudes more likely to inhibit the population growth of a globally distributed aphid?

Meta-analysis reveals less sensitivity of non-native animals than natives to extreme weather worldwide

Extreme weather events (EWEs; for example, heatwaves, cold spells, storms, floods and droughts) and non-native species invasions are two major threats to global biodiversity and are increasing in both frequency and consequences. Here we synthesize 443 studies and apply multilevel mixed-effects metaregression analyses to compare the responses of 187 non-native and 1,852 native animal species across terrestrial, freshwater and marine ecosystems to different types of EWE. Our results show that marine animals, regardless of whether they are non-native or native, are overall insensitive to EWEs, except for negative effects of heatwaves on native mollusks, corals and anemone. By contrast, terrestrial and freshwater non-native animals are only adversely affected by heatwaves and storms, respectively, whereas native animals negatively respond to heatwaves, cold spells and droughts in terrestrial ecosystems and are vulnerable to most EWEs except cold spells in freshwater ecosystems. On average, non-native animals displayed low abundance in terrestrial ecosystems, and decreased body condition and life history traits in freshwater ecosystems, whereas native animals displayed declines in body condition, life history traits, abundance, distribution and recovery in terrestrial ecosystems, and community structure in freshwater ecosystems. By identifying areas with high overlap between EWEs and EWE-tolerant non-native species, we also provide locations where native biodiversity might be adversely affected by their joint effects and where EWEs might facilitate the establishment and/or spread of non-native species under continuing global change.

Heat-avoidance behavior associates with thermal sensitivity rather than tolerance in aphid assemblages

How to predict animals' heat-avoidance behaviors is critical since behavior stands the first line for animals dealing with frequent heat events under ongoing climate warming. However, the discrepancy between the scarcity of research on heat-avoidance behaviors and the commonness of eco-physiological data for thermal tolerance and for thermal sensitivity such as the temperature-dependent survival time makes it difficult to link physiological thermal traits to heat-avoidance behavior. Aphids usually suck plant sap on a fixed site on the host plants at moderate temperatures, but they will leave and seek cooler feeding sites under stressful temperatures. Here we take the cereal aphid assemblages comprising different species with various development stages as a model system. We tested the hypotheses that heat tolerance (critical thermal maximum, CT_max) or heat sensitivity (temperature-dependent declining rate of survival time, similarly hereinafter) would associate with the temperature at which aphid activate heat-avoidance behavior. Specifically, we hypothesized the aphids with less heat tolerance or greater heat sensitivity would take a lower heat risk by leaving the host plant earlier. By mimicking the linear increase in ambient temperature during the daytime, we measured the CT_max and the heat-avoidance temperature (HAT, at which aphids leave the host plant to find cooler places) to understand their heat tolerance and heat-avoidance behavior. Then, we tested the survival time of aphids at different temperatures and calculated the slope of survival time declining with temperature to assess their heat sensitivity (HS). Finally, we examined the relationships between CT_max and HAT and between HS and HAT to understand if the heat-avoidance behavior associates with heat tolerance or with heat sensitivity. The results showed that HS and HAT had a strong correlation, with more heat sensitive individuals displayed lower HAT. By contrast, CT_max and HAT had a weak correlation. Our results thus provide evidence that heat sensitivity is a more reliable indicator than thermal tolerance linking with the heat-avoidance behavior in the aphid assemblages. Most existing studies use the indexes related to thermal tolerance to predict warming impacts. Our findings highlight the urgency to incorporate thermal sensitivity when predicting animal responses to climate change.

Establishing a warning index for evaluating the physiological stress of sanitation workers in high temperature weather

High temperature weather occurs frequently in recent years. As a heat-vulnerable group, sanitation workers suffer great physiological safety risks in high temperature weather. In this paper, a physiological warning index (PWI) is established to quantify the physiological stress of the sanitation workers. Firstly, the dynamic weights of the physiological parameters are calculated by the norm grey correlation method. Secondly, the PWI is established by the efficacy coefficient method and the warning level of the PWI is divided based on the relationships between the PWI and thermal sensation vote (TSV). Finally, the reasonability of the PWI is verified. The results show that the weights of the physiological parameters are dynamic, changing with the environments and the physiological states. The weight ranges of the mean skin temperature (MST), tympanic temperature (TT), systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) are 0.036-0.538, 0.000-0.369, 0.000-0.362, 0.018-0.367 and 0.009-0.348. And the MST and DBP are more affected by the high temperature than the TT, SBP and HR. The warning interval of PWI is: (0, 0.25] (no warning), (0.25, 0.45] (mild warning), (0.45, 0.7] (moderate warning), and (0.7, 1.0] (severe warning). The PWI can provide simple real-time physiological warning and guarantee physiological health for sanitation workers in high temperature weather.