Abstract
The dynamics of host-parasite interactions are highly temperature-dependent and may be modified by increasing frequency and intensity of climate-driven heat events. Here, we show that altered patterns of temperature variance lead to an almost order-of-magnitude shift in thermal performance of host and pathogen life-history traits over and above the effects of mean temperature and, moreover, that different temperature regimes affect these traits differently. We found that diurnal fluctuations of ±3°C lowered infection rates and reduced spore burden compared to constant temperatures in our focal host Daphnia magna exposed to the microsporidium parasite Ordospora colligata. In contrast, a 3-day heatwave (+6°C) did not affect infection rates, but increased spore burden (relative to constant temperatures with the same mean) at 16°C, while reducing burden at higher temperatures. We conclude that changing patterns of climate variation, superimposed on shifts in mean temperatures due to global warming, may have profound and unanticipated effects on disease dynamics.
Highlights
One of the major challenges of the 21st century is understanding how infectious diseases, which have profound ecological and epidemiological impacts on human (Hotez et al, 2014), agricultural (Chakraborty and Newton, 2011), and wildlife (Harvell et al, 2019) populations, will be affected by climate change
Diurnal temperature fluctuations narrowed the thermal performance curve for infectivity compared with constant temperatures (Figure 2A)
The thermal performance curve for infectivity under the heatwave, where temperatures were raised by 6°C for 3 days and returned to constant temperature (Figure 1), was almost identical to that under constant temperature
Summary
One of the major challenges of the 21st century is understanding how infectious diseases, which have profound ecological and epidemiological impacts on human (Hotez et al, 2014), agricultural (Chakraborty and Newton, 2011), and wildlife (Harvell et al, 2019) populations, will be affected by climate change It is well-established that the interaction between hosts and their pathogens is sensitive to temperature (Kirk et al, 2020; Rohr et al, 2013). Disease transmission (Ben-Horin et al, 2013), host immunity (Dittmar et al, 2014; Rohr and Raffel, 2010), and pathogen growth (Gehman et al, 2018; Kirk et al, 2018) can increase with temperature, while other host-p athogen life-h istory traits such as lifespan and fecundity can decrease (Altizer et al, 2013).
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