Pre-copulatory choices drive post-copulatory decisions: mechanisms of female control shift across different life stages.

Background: The 'wallflower' hypothesis proposes females mate indiscriminately to avoid reproductive delays. Post-copulatory mechanisms may then allow 'trading up', favouring paternity of future mates. We tested links between pre- and post-copulatory choice in Latrodectus geometricus female spiders paired sequentially with two males. These females copulate as adults or as subadults and store sperm in paired spermathecae. Choosy adults have a higher risk of delays to reproduction than subadults.

Results: We predicted low pre-copulatory, but high post-copulatory choice at first matings for adults and the opposite for subadults. At second matings, we expected all females would prefer males superior to their first. We found all females mated indiscriminately at their first pairing, but in contrast to subadults, adults usually allowed only a single insertion (leaving one of their paired spermatheca empty); a mechanism of post-copulatory choosiness. Adult-mated females were more likely to remate than subadult-mated females when they became adults, showing a preference for larger males, while subadult-mated females tended to prefer males of greater size-corrected mass.

Conclusions: Our results show that the 'wallflower' effect and 'trading up' tactics can be utilized at different life stages, allowing females to employ choice even if rejecting males is costly.