Sexual selection buffers the negative consequences of population fragmentation on adaptive plastic responses to increasing temperatures

Whether sexual selection facilitates or hampers the ability to plastically
respond to novel environments might depend on population structure, via
its effects on sexual interactions and associated fitness payoffs. Using
experimentally evolved lines of the seed beetle Callosobruchus maculatus,
we tested whether individuals evolving under different sexual selection
(monogamy vs polygamy) and population spatial structure (metapopulation vs
undivided populations) treatments differed in their response across
developmental thermal conditions (control, hot or stressful) in a range of
fitness and fitness-associated traits. We found that individuals from
subdivided populations had lower lifetime reproductive success (LRS) at
hot temperatures, but only in lines evolving under relaxed sexual
selection, revealing a complex interaction between sexual selection,
population structure, and thermal environmental stress on fitness. We also
found an effect of population structure on several traits, including
fertility and adult emergence success, under exposure to high thermal
conditions. Finally, we found a strong negative effect of hot and
stressful temperatures in fitness and associated traits. Our results show
that population structure can exacerbate the impact of a warming climate,
potentially leading to declines in population viability, but that sexual
selection can buffer the negative influence of population subdivision on
adaptation to warm temperatures.