Data from: Realistic heat pulses protect frogs from disease under simulated rainforest frog thermal regimes

Recent emergences of fungal diseases have caused catastrophic global
losses of biodiversity. Temperature is one of the most important factors
influencing host-fungus associations but the effects of temperature
variability on disease development are rarely examined. The chytrid
pathogen Batrachochytrium dendrobatidis (Bd) has had severe effects on
populations of hundreds of rainforest-endemic amphibian species but we
know little about the effects of rainforest-specific host body temperature
cycles on infection patterns. To address this challenge, we used body
temperature regimes experienced in nature by frogs in the Australian Wet
Tropics to guide a controlled experiment investigating the effects of body
temperature fluctuations on infection patterns in a model host (Litoria
spenceri), with emphasis on exposing frogs to realistic ‘heat pulses’ that
only marginally exceed the thermal optimum of the fungus. We then exposed
cultured Bd to an expanded array of heat pulse treatments and measured
parameters of population growth to help resolve the role of host immunity
in our in vivo results. Infections developed more slowly in frogs exposed
to daily 4-h heat pulses of 26°C or 29°C than in frogs in constant
temperature treatments without heat pulses (control). Frogs that
experienced heat pulses were also less likely to exceed infection
intensities at which morbidity and mortality become likely. Ten of 11
(91%) frogs from the daily 29°C heat pulse treatment even cleared their
infections after approximately nine weeks. Cultured Bd also grew more
slowly when exposed to heat pulses than in constant-temperature control
treatments, suggesting that mild heat pulses have direct negative effects
on Bd growth in nature, but precluding us from determining whether there
was a concurrent benefit of heat pulses to host immunity. Our results
suggest that even in habitats where average temperatures may be suitable
for fungal growth and reproduction, infection risk or the outcome of
existing infections may be heavily influenced by short but frequent
exposures to temperatures that only slightly exceed the optimum for the
fungus. Our findings provide support for management interventions that
promote warm microenvironments for hosts, such as small-scale removal of
branches overhanging critical habitat or provision of artificial heat
sources.