Considerable evidence exists for local adaptation of critical thermal limits in
ectotherms following adult temperature stress, but fewer studies have tested for local
adaptation of sub-lethal heat stress effects across life history stages. In organisms
with complex life cycles, such as holometablous insects, heat stress during ...
Considerable evidence exists for local adaptation of critical thermal limits in
ectotherms following adult temperature stress, but fewer studies have tested for local
adaptation of sub-lethal heat stress effects across life history stages. In organisms
with complex life cycles, such as holometablous insects, heat stress during juvenile
stages may severely impact gametogenesis, having downstream consequences on
reproductive performance that may be mediated by local adaptation, although this is
rarely studied. Here, we tested how exposure to either benign or heat stress
temperature during juvenile and adult stages, either independently or combined,
influences egg-to-adult viability, adult sperm motility and fertility in high and low
latitude populations of Drosophila subobscura. We found both population- and
temperature-specific effects on survival and sperm motility; juvenile heat stress
decreased survival and subsequent sperm motility and each trait was lower in the
northern population. We found an interaction between population and temperature
on fertility following application of juvenile heat stress; while fertility was negatively
impacted in both populations, the southern population was less affected. When the
adult stage was also subject to heat stress, the southern population exhibited
positive carry-over effects whereas the northern population’s fertility remained low.
Thus, the northern population is more susceptible to sub-lethal reproductive
consequences following exposure to juvenile heat stress. This may be common in
other organisms with complex life cycles and current models predicting population
responses to climate change, which do not take into account the impact of juvenile
heat stress on reproductive performance, may be too conservative