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Title: The impacts of heat-wave conditions on reproduction in a model insect, Tribolium castaneum
Author: Dickinson, Matthew
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2018
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Climate change will increase the frequency, intensity and duration of weather extremes including heat-waves, which could have important consequences for biodiversity. This thesis examines the direct influences of thermal stress associated with heat-wave conditions on reproduction in a model insect in order to understand how animal populations might be affected by climate change. Fertility reductions in homeotherms due to thermal stress are well documented, but effects on ectotherms have received little attention. In the first half of this thesis, the flour beetle model Tribolium castaneum is used to measure the impacts of heat-wave conditions on reproductive fitness in males and females, and the proximate mechanisms behind any impacts. I find that the reproductive fitness of males, but not females, is impacted by heat-wave conditions. Female fecundity is not affected when mating with heat stressed males, but egg hatch and pupal eclosion rates are reduced. Transgenerational effects were not found beyond the pupal stage. In experimental examinations of mating behaviour, males exposed to heat-wave conditions were slower to initiate mating and mated less frequently, but still achieving sufficient matings that would normally allow full female fertility. However, ejaculate sperm numbers were reduced more than five-fold following a simulated heat-wave, partly explaining how male reproductive fitness is halved following exposure to a heat-wave. In addition to an impact on male fertility and sperm production, I also found clear evidence that sperm in female storage were also sensitive to heat-wave conditions, with significant declines in female reproductive fitness if they had already mated and contained sperm, but no effects if the heat-wave was experienced before mating and sperm storage. This sensitivity of male fertility to heat-wave conditions could generate selection on both males and females to respond. In the second half of the project, the male and female responses to thermal stress and their impacts across generations were investigated. Females were found to be able to rescue their fertility when facing matings with heat stressed males by mating polyandrously, restoring their reproductive output to normal levels. However, I found no evidence that females strategically or facultatively adjusted their remating behaviour to compensate for reductions in fertility condition after thermal stress, and multi-generational male responses to elevated ambient temperature regimes showed no evidence for an ability to acclimate or adapt to heat-wave conditions. This thesis advances our knowledge of how one important trait for population viability and biodiversity can be impacted by climate change and increases in extreme weather conditions. It offers directions for future research to investigate the drivers of temperature-induced male fertility loss, and suggestions for how management efforts might be focused to mitigate the impacts of heat-wave conditions on reproduction in ectotherms.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available