Female mating rates and their fitness consequences in the common house spider Parasteatoda tepidariorum

Mating systems, with varying female mating rates occurring with the same partner (monandry) or with multiple mates (polyandry), can have far reaching consequences for population viability and the rate of gene flow. Here, we investigate the mating rates 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 (monandry) or with different males (polyandry), and recorded behaviors, mating success and fitness resulting from single- and double-matings, either monandrous or polyandrous. Despite the study being explorative in nature, we predict successful matings to be more frequent during first encounters, to reduce female 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 did not mate, and those that did mated only once, not necessarily on their first encounter. The likelihood of re-mating did not differ between monandrous and polyandrous encounters and female mating experience (mated once, twice monandrous, twice polyandrous) did not affect fitness, indicated by similar offspring production. Female twanging of the web leads to successful matings suggesting female behavioral receptivity. Cannibalism rates were low and mostly occurred pre-copulatory. We discuss how the species ecology, with potentially high mating costs for males and limited female receptivity, may shape a mating system with low mating rates.