Date of Award
Doctor of Philosophy (PhD)
Petrella, Lisa N.
Sexual reproduction and its coincident genetic recombination are powerful adaptive strategies. However, sexual reproduction has disadvantages. One ancient and conserved disadvantage is temperature sensitivity. In organisms diverse as plants, insects, nematode worms, and humans, as temperatures increase, fertility decreases. The goal of this dissertation is to examine the negative impact of elevated temperature stress on fertility in sexually reproducing organisms using wild strains of Caenorhabditis elegans. C. elegans presents a unique opportunity to study these effects broadly in two contexts, as worms may be either self-fertile hermaphrodites that produce both egg and sperm or males which produce only sperm. In chapters III and IV, I delineate the negative impact of moderate temperature stress on C. elegans males in three wild strains. I demonstrate that contrary to what has been shown in some animals, temperature stress has minor effects on germline-associated processes like sperm production, quality, and motility. These effects are overshadowed by comparatively dramatic changes in male behavior. Temperature stressed males experience a dramatic upset in their feeding and mating drives due to an inability to properly respond to external stimuli and make suitable decisions. Thus, very few temperature stressed males reproduce successfully and those that do produce few progeny. In chapter V, I report on the variability in fertility under temperature stress in C. elegans hermaphrodites in 144 wild strains isolated from across the globe. These strains vary considerably in both the percentage of fertile animals in the test population and the brood sizes of fertile individuals. I performed genome-wide association (GWA) mapping which identified quantitative trait loci (QTL) underlying the phenotypic variation I observed in brood size. These QTL do not correspond with known QTL identified by assessing lifetime fecundity at ideal temperatures, suggesting that there are distinct temperature sensitive elements of fertility highlighting its complexity. Collectively, this dissertation demonstrates exposure to modestly elevated temperatures has considerable and negative effects on fertility with significant differences dependent upon genetic variation. As climate change associated temperature variability becomes more commonplace, it will be imperative to understand how temperature stress affects conserved elements critical to sexual reproduction.
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