Dissertation Research: Eggs in one basket: Male mate choice and female mortality risk in a sperm-limited spider

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Do animals consider their partner's mortality risk when choosing a mate? In the golden orb spider, Nephila clavipes, males are limited in the amount of sperm they can use over their lifetime and therefore must allocate sperm judiciously. They usually choose to mate with unmated females because the first male to mate with a virgin female fertilizes the majority of her eggs. However, a virgin female stores sperm and delays egg fertilization for up to a month, making it possible that she will die before she lays her eggs. If she dies then the male has wasted his limited sperm on this female. Rather than mate with a virgin, some males mate with a previously mated female just before she lays her eggs. This study proposes that these males are trading off reduced paternity for an increase in the chance that his mate will survive to lay eggs, a portion of which he has fertilized. Mate mortality risk could be a factor in mate choice under a variety of circumstances where reproductive pay-off is not immediate. For example, in species with paternal care, females are thought to choose mates that are in good condition because they provide more resources, but this study suggests a different reason: lower parental mortality rates that will reduce offspring abandonment. This project uses modeling, molecular and experimental approaches to evaluate this hypothesis. The investigators will measure the consequences of mating choices by males and how these consequences change over the breeding season. The project will provide undergraduate assistants with research experience in observational field methods, natural experiments, genetic analysis, and dynamic modeling. In addition, the study will contribute to the campus natural areas conservation project. Understanding the complexity of reproductive behavior is critical for conservation efforts and for maintaining biodiversity.