2b) Fertility after adult heat-stress
Adult males were given an initial group of virgin females to mate with,
and there was no interaction between stress temperature and hardening
treatment on immediate fertility of adult males
(χ2(1) = 0.244, p=0.621; Figure 2b,
days 13-19). We also found no effect of heat-stress on immediate
fertility (χ2(1) = 2.286, p=0.130;
Figure 4, days 13-19), and no main effect of hardening on fertility at
this initial time point (χ2(1) =
0.590, p= 0.443; Figure 2b, days 13-19).
From 7 days post heat-stress onwards in non-hardened flies, there was no
interaction between heat-stress and time
(χ2(1) 3.333, p=0.068; Figure 2b, days
19-27). However, we found that heat stress significantly reduced
fertility through a main effect of stress
(χ2(1) = 28.444, p< 0.001;
Figure 2b, days 19-27). Stressed males had lower fertility than controls
after 7 days post heat-stress. We found no significant effect of time on
fertility after day 7 (χ2(1) = 2.413,
p= 0.120; Figure 2b, days 19-27) meaning fertility remained low post 7
days.
There was no interaction between hardening and time on fertility at the
stress temperature of 34°C when measured after day 7
(χ2(1) = 2.1824, p= 0.140; Figure 2b,
days 19-27). Hardening also did not affect fertility of heat-stressed
adults (χ2(1) = 0.1319, p= 0.717;
Figure 2b, days 19-27) meaning hardening does not change the sterility
pattern induced by thermal stress, even though there was a main effect
of time on fertility (χ2(1) = 4.265,
p= 0.039; Figure 2b, days 19-27), where fertility increased slightly as
the experiment progressed.