Although it is generally accepted that females can gain material benefits by mating with more than one male, the proposal that polyandry provides genetic benefits remains controversial, largely because direct experimental support is lacking. Here, we report the results of a study testing for genetic benefits to polyandry in the pseudoscorpion Cordylochernes scorpioides. In an experiment that controlled for male mating experience and the number of spermatophores accepted by a female, twice-mated females received either one sperm-packet from each of two different males (the ''DM'' treatment) or two sperm-packets from a single male (the same male or ''SM'' treatment). Over their lifetime, DM females gave birth to 32% more offspring than did SM females, primarily because of a significantly reduced rate of spontaneous abortion. This result could not be attributed to male infertility nor to lack of sexual receptivity in males paired with previous mates. Spermatophore and sperm numbers did not differ between males presented with a previous mate and males paired with a new female. Because SM and DM females received the same quantity of ejaculate, it was possible to eliminate material benefits as a contributor to the enhanced reproductive success of DM females. The reduction in embryo failure rate achieved by DM females is most consistent with the genetic incompatibility avoidance hypothesis, i.e., that polyandry enables females to exploit postcopulatory mechanisms for reducing the risk and͞or cost of fertilization by genetically incompatible sperm. This study, which rigorously controlled for material benefits and excluded inbreeding effects, demonstrates that polyandry provides genetic benefits that significantly enhance female lifetime reproductive success.The revolution in molecular genetic techniques that has taken place over the past decade has revealed one of nature's best-kept secrets, namely, that across a wide array of species, females frequently mate with more than one male (1, 2). As DNA evidence of multiple paternity accumulates for organisms as ecologically and phylogenetically divergent as fruit flies (3) and humpback whales (4), it is becoming clear that polyandry is a common female mating strategy, although it is often covert and difficult to detect at the behavioral level. Polyandry as a pervasive feature of natural populations challenges the long-held view of females as the choosy, monogamous sex (5-7) and raises the question of why, considering the potentially high risks and costs involved, females would mate with multiple males (8-9).As evolutionary biologists increasingly recognize the importance of considering reproduction from the female perspective (10), a variety of hypotheses have been proposed to explain why selection should favor the evolution of polyandry. With

In most animal species, particularly those in which females engage in polyandry, mate choice is a sequential process in which a female must choose to mate or not to mate with each male encountered. Although a number of theoretical and empirical investigations have examined the effects of sequential mate choice on the operation of sexual selection, how females respond to solicitation by previous mates has received little attention. Here, we report the results of a study carried out on the polyandrous pseudoscorpion, Cordylochernes scorpioides, that assessed the sexual receptivity of once-mated females presented after a lapse of 1.5 hr or 48 hr with either their first mate or a different male. Females exhibited a high level of receptivity to new males, irrespective of intermating interval. By contrast, time between matings exerted a strong effect on female receptivity to previous mates. After a lapse of 48 hr, females did not differ significantly in their receptivity toward previous mates and different males, whereas at 1.5 hr after first mating, females were almost invariably unreceptive to males from whom they had previously accepted sperm. This result could not be attributed to male size or mating experience or to male sexual receptivity. Indeed, males were as willing to transfer sperm to a previous mate as they were to a new female. This difference between males and females in their propensity to remate with the same individual may ref lect a conf lict between the sexes, with males seeking to minimize postcopulatory sexual selection and females actively keeping open the opportunity for sperm competition and female choice of sperm by discriminating against previous mates.

Patients with hereditary angioedema (HAE) have impaired health-related quality of life (HRQoL), but the effect of preventative treatment strategies on HRQoL has not been evaluated. This study was designed to evaluate the effect of routine prevention therapy with nanofiltered C1 inhibitor (C1 INH-nf; human) on the HRQoL of patients with HAE. Thiry-six-item Short Form (SF-36) Version 1.0 questionnaires were administered at the beginning and end of two 12-week treatment periods in this multicenter, randomized, placebo-controlled, crossover study. Patients (n = 22) received intravenous injections of 1000 U of C1 INH-nf or placebo every 3-4 days for 12 weeks and then crossed over to the other treatment arm for a second 12-week period. Patients could receive open-label C1 INH-nf (1000 U) for the acute treatment of angioedema attacks in either arm of the study. Sixteen patients had evaluable SF-36 data. Mean physical component summary scores (PCSs) were 36.41 at baseline, 37.06 at the end of the placebo period, and 43.92 at the end of the C1 INH-nf period. Mean mental component summary scores (MCSs) were 49.90, 44.98, and 54.00, respectively. Least square mean differences (95% confidence intervals) between C1 INH-nf and placebo in norm-based SF-36 scores at the end of each treatment period were 6.55 (1.48, 11.62; p = 0.015) for PCS and 8.70 (1.67, 15.72; p = 0.019) for MCS. In a clinical trial setting, patients with HAE had significantly better HRQoL after 12 weeks of C1 INH-nf for routine prevention compared with acute treatment of individual angioedema attacks in the absence of routine prevention while on placebo. This study was a part of the clinical trial NCT01005888 registered in www.clinicaltrials.gov.