The mating system of the common house spider Parasteatoda tepidariorum

Mating systems, with varying female mating rates occurring with the same partner (monogamy) or with multiple mates (polyandry), can have far reaching consequences for population viability and the rate of gene flow. Here, we investigate the mating system of the common house spider Parasteatoda tepidariorum (Theridiidae), an emerging model for genetic studies, with yet undescribed reproductive behavior. It is hypothesized that spiders belonging to this family have low re-mating rates. We paired females twice with the same male (monogamy) or with different males (polyandry), scored behaviors and mating success and fitness resulting from single- and double-matings, either monogamous or polyandrous. Despite the study being explorative in nature, we predict successful matings to be more frequent during first encounters, to reduce the risk of remaining unmated. For re-mating to be adaptive, we expect higher fitness of double-mated females, and polyandrous females to experience highest mating success and fitness if reproductive gains are achieved by mating with multiple partners. We show that the majority of the females mated once, not necessarily on their first encounter, and the likelihood of re-mating did not differ between monogamous and polyandrous encounters. The number of matings did not affect fitness, indicated by similar offspring production in females. Female twanging of the web, a behavior that likely advertises female receptivity, lead successful matings, suggesting female control. We discuss how the species ecology, with high mating costs for males and potentially limited female receptivity, may shape a mating system with low mating rates.