ZEFI-PTR-G-ThermalChallenge

In a rapidly warming world, exposure to high temperatures may impact
fitness, but the gene regulatory mechanisms that link sublethal heat to
sexually selected traits are not well understood, particularly in
endothermic animals. Our experiment used zebra finches (Taeniopygia
guttata), songbirds that experience extreme temperature fluctuations in
their native Australia. We exposed captive males to an acute thermal
challenge (43°C) compared with thermoneutral (35°C) and lower (27°C)
temperatures. We found significantly more heat dissipation behaviors at
43°C, a temperature previously shown to reduce song production and
fertility, and more heat retention behaviors at 27°C. Next, we
characterized transcriptomic responses in tissues important for mating
effort – the posterior telencephalon, for its role in song production, and
the testis, for its role in fertility and hormone production. Differential
expression of hundreds of genes in the testes, but few in the brain,
suggest the brain is less responsive to extreme
temperatures. Nevertheless, gene network analyses revealed that
expression related to dopaminergic signaling in the brain co-varied with
heat dissipation behaviors, providing a mechanism by which temporary
thermal challenges may alter motivational circuits for song
production. In both brain and testis, we also observed
correlations between thermally sensitive gene networks and individual
differences in thermoregulatory behavior. Although we cannot directly
relate these gene regulatory changes to mating success, our results
suggest that individual variation in response to thermal challenges could
impact sexually selected traits in a warming world.